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JFNM 07-21-2015 04:56 AM

Quote:

Originally Posted by Samflhomes (Post 2656663)
Gas heater works fine but not electric

Hi Sam,

This is probably of no help but... just in case. ;)

Some water heaters have two switches. One on the control panel (with all the other electrical goodies and another on the water heater itself. Both have to be on for the 120V heating element to work. The switch on my water heater is pretty small and inconspicuous (not labeled).

ShapeShifter 07-21-2015 06:25 AM

Sam,

I can answer your questions, but that's going to be too much typing on a little tablet. I'll be back at my computer in an hour or two, and will give a full response when I have a real keyboard on monitor - it's much more efficient that way!

Hopefully it'll be before you head back out to work on it some more.

Quote:

Originally Posted by JFNM (Post 2659202)
Hi Sam,



This is probably of no help but... just in case. ;)



Some water heaters have two switches. One on the control panel (with all the other electrical goodies and another on the water heater itself. Both have to be on for the 120V heating element to work. The switch on my water heater is pretty small and inconspicuous (not labeled).


Good suggestion, but it doesn't apply to this heater, there are no switches in the heater itself. The wiring diagram is posted above. The electric heater circuit is about as simple as it gets: if the relay is on, and there is incoming power, the heater is on. The actual low voltage controls are a bit more complicated, but there are still no local controls.

YC1 07-21-2015 06:29 AM

You may shoot yourself in the foot if you keep digging. No offense, it happens.

Do you have 12 volts on the wall switch?
No need to be digging around a relay if 12 volts is not getting to the switch or out of it.

To measure that voltage with confidence you need a good ground for the negative/black lead of your meter. Grab a regular extension cord and plug it into a wall outlet in the rv. Put tape over the long holes of the open end. This leaves the ground wire. Slide a round tight fitting screwdriver into the round ground hole if you can, otherwise just hold the negative lead tightly or tape it. Make some test measurements on a working ceiling light or something that is 12 volts so you again have confidence.

Now see if there is voltage on the switch leads on the wall. Check both contacts on the switch. If you find 12 volts one one side, turn the switch on. If 12 volts on the other side this is the time to go to the heater relay.

I suspect you may have a blown fuse supplying the 12 volts so if the voltage is not present then it is time to hunt fuses. Some are hidden and some are just not easy to see.

I like to use a 12 volt test light versus a meter for this test. Using the extension cord ground go to any fuse panels you find and put the meter or better yet the test light probe on each side of the fuses. Check each end. If you find power on one end and not the other then change and label that fuse.

If you cannot find it then a Fox and Hound is a great tool that will sort it out.

ShapeShifter 07-21-2015 08:51 AM

WARNING: Let me start by re-iterating that you are working with potentially dangerous voltages at the back of the water heater, and in the circuit breaker box if it gets that far. KEEP THE AC CIRCUIT BREAKER FOR THE WATER HEATER TURNED OFF! Better yet, completely unplug the shore power and make sure the generator doesn't start. The only time you should turn on the AC breaker is when you are specifically measuring an AC voltage, and before doing that you must make sure than any exposed wires are not shorting against anything. Be very careful working around exposed live wires! You can be seriously injured or killed! :eek:

Now, go back and read that paragraph again!

OK, now you can proceed, but please read through and understand everything in the remainder of this post before continuing your work.

Quote:

Originally Posted by YC1 (Post 2659262)
Do you have 12 volts on the wall switch?
No need to be digging around a relay if 12 volts is not getting to the switch or out of it.

I agree. That's why the first test I recommended was checking the white wire into the heater - that's the control signal from the switch. I figured it was easiest to get to the signal there, where it's easily accessible and a ground is handy, rather than opening up the control panel and then looking for a good ground.

But if the white wire does not have the control signal on it, that is what is going to be needed, so you have some great advice there. :thumb:

Actually, looking back, checking the control signal is the second test I list. The first thing I have is checking that the heater element isn't internally shorted to ground, a test I only listed because Sam seemed to be particularly concerned that the element was bad. As long as everything is currently exposed, and he already started those tests, I figured it didn't hurt to finish them. Even though it's unlikely to be a problem, it's a good safety test as long as everything is already open.

To be clear: most of what I wrote is to diagnose problems within the water heater itself. That test to measure the 12V coming in on the white wire is critical and should not be skipped: if there is no voltage coming in on that wire, the problem is NOT in the water heater, it's in that control circuit which is part of the coach's wiring. I have no details of that wiring, so you're going to be on your own following the general advice given by Myron.

Quote:

Originally Posted by Samflhomes (Post 2659135)
and that my EMS is a portable that I add at the post when I plug in at rv for park.

That really shouldn't play into this. As long as you are getting AC power into the coach for other loads, that style of EMS is not the cause of your water heater issues.

The confusion is that the term EMS is applied to two very different types of systems: The type you have monitors the incoming power and will disconnect the coach if various issues are detected like high/low voltage, certain wiring problems, etc.

The other type doesn't do any of that. Instead, it monitors the type of power you have (generator, 50 Amp, 30 Amp, 20 Amp) and the amount of power you are currently using. If you are trying to use more current than is available from the power source, it will automatically start to shut off less important loads to bring the total power consumption into the safe range. For my system, it will first cut power to the water heater, then the rear A/C, then the washer/dryer, then the front A/C. I wanted to know if you had such a system because the electric water heater circuit is usually one of the first things that such a system would cut off. I have had times where that EMS system has locked up and needed to be reset, and one of the symptoms is that the loads it controls are disabled. I wanted to make sure you did not have such a system, or if you did, that it was working properly.

Quote:

I also have removed the two ground ( I think they are both used for grounds?) wires from lugs on back of tank and the white black from the element
Yes, the lug on the back of the tank will be ground. There should be two wires on that lug (there is no need to remove them, and I would recommend connecting them back up before getting into these tests.)
  • One of the wires is the ground wire (probably green) from the incoming power cord. This is the safety ground for the circuit.
  • The other of these wires will go directly to one of the coil terminals of the relay. This is the wire that completes the circuit to the relay, the relay will not activate if that wire is disconnected.

On the heater element, the black wire is the hot lead and should always have 120V when measured to the white wire. This lead should go to one of the relay contact terminals. The white wire on the element is the neutral wire and should be coming directly from the input power cord.

Quote:

Then I checked from the white and black terminals to the lugs and got ol but in my ignorance thought it meant zero so now I understand it's really high resistance.
What reading means low resistance? As you described it.
Take your meter, and set it to the resistance measuring mode (the Greek Omega symbol between the ACV and ACmA settings on your meter.) Now, touch the contacts of the two probes directly together, and the display should read close to zero (it usually never reads exactly zero, as there is always some resistance in the probes themselves.) A typical value might be around 0.4. This is how zero resistance will read on your meter.

Now, separate the two meter probes so that are not touching each other. The display will likely show "OL" which should look significantly different than the previous display indication. This is how the meter displays an open circuit (infinite resistance.)

For the sake of these tests, a low resistance is generally anything less than an Ohm or two. If you are reading more than that, make sure the probes are touching clean metal contact points and that they are making good contact. A loose connection or dirty contact point can throw of the measurement.

Quote:

Starting with the point you having me check the white wire on control board I'll use pressure relief for the black probe and do you think the red probe will hit the white wire since it is buried into the connector on control panel or should I pull it and check from the other side that plugs in? Or is there some way I can get probe down those little holes in the connector?
You may or may not be able to fit the probe next to the wire in the hole far enough to make contact. It all depends on the thickness of the probe contact, and the available space in the hole. One tip (for the low voltage DC connections only!) is to straighten a paperclip: that can usually be pushed in far enough to make contact, then you can touch the probe to the paperclip - just make sure the paperclip can't short to anything.

For measuring the white wire, you can indeed pull off the connector and measure from the other side of the connector.

But for the the yellow wire, that won't work as the power is coming from the control board. If you simply can't probe the back of the connector, pull off the connector and probe the corresponding contact on the control board.

Quote:

I'll try to keep water somewhat cold so that the yellow wire should show voltage at the control panel when the 12v switch is on.
An easy way to tell if the water is cold enough is to flip on the gas control switch: the gas flame should light within seconds. If it doesn't, the water is too warm and the yellow wire will not have power by design. Just make sure to flip the gas control switch off again or the water will heat up to the point where the yellow wire will definitely be off. If you are testing the yellow wire, and the gas flame does not light, run enough hot water to make the gas flame come on, then turn off the gas mode switch and make your yellow wire test.

Quote:

However does it matter that all the 4 wires described above are still not attached to the rear of the tank?
Yes. The steps I mentioned before assume that everything is connected as it was before you started anything. The only wires that should be disconnected are whatever wires I mention in that particular step. For example, with that wire from the relay disconnected from the ground lug in back, the relay will never switch on, even if it is getting the proper voltage.

Quote:

So when I get to the relay I need to find a good ground with the black and touch the yellow in the relay
Yes. That lug for the ground wires is a good ground point.

Quote:

There are two wires that go to the back of heater I think they are green but one may be black. At least one comes from the relay. I am not sure where the other comes from and J don't know how to identify the power cord you mentioned It must be on top of heater and I haven't seen it and access to top of heater is extremely challenging since I am on my back already trying to reach up to the relay and element . I think we need to clarify what these two wires are that attach to the heater lugs (bolts) so I check the correct one and understand the purpose of the other one.
The power cord is attached to the box covering the relay and the heater element. In the drawing below, there is a rounded line at the left side of that box, near the bottom. This is a clamp that holds the incoming power cord in place.

https://www.ssav.org/RV/pics/WaterHeaterRelay.gif

Look at the wiring diagram I posted previously: the AC circuit is in the lower left corner. The power cord is drawn as the three wires coming in from the bottom left: 115V NEUTRAL (white), 115V HOT (black) and GRN (the green ground wire.) The dotted line represents where these wires enter the water heater (the clamp on the box that covers the relay/element. Following the circuit:
  • The black wire from the power cord goes to one of the relay contacts (labeled BLACK 110V HOT in the diagram immediately above)
  • A black wire run from another relay contact to one lug of the heater element (labeled BLACK TO ELEMENT above)
  • The other lug of the heater element is connected to the white wire from the power cord, completing the circuit (not shown in the above diagram)
  • The last wire of the power cord is the green ground, connected to the stud on the back of the water heater (that triangular symbol of three lines in the wiring diagram means a ground connection.)

Quote:

When you say high resistance is that the ol again?
Yes.

Quote:

What is very low resistance on the meter look like? Need to know the digital value you are implying.
Probably something less than an Ohm or so (zero point something.)

Quote:

I am curious if my heater is hard wired or there is a hidden plug somewhere near the top of heater
Maybe it's loose.
I can't say. My power cord looks like a regular heavy duty extension cord, and is plugged into a regular socket behind the water heater. Yours might be the same, or the wire from the breaker box might go directly to the heater. The only way to know is to start where the cord comes out of the relay box and follow it to see where it goes.

One final comment: before starting anything, re-read the initial warning paragraph at the start of this post!

Good luck!

Samflhomes 07-21-2015 03:49 PM

Ok Thank You I will go slow and see what I find Out
Your instructions are at a level that I can understand and follow

Will report back

Sam

Samflhomes 07-21-2015 05:13 PM

There are still no wires connected to back of water heater.

I wanted to quick check the 12 volt white wire coming from the inside switch so I turned it on.

Went to the control board and pulled the connector and checked the back side of the white. Got 13.4 . (For clarification I turned meter on to DCV and was surprised to see number Ike 65.7 etc but when I grounded the black lead to the relief valve and put the red on the white lead I got 13.4)

Now I checked the yellow on the other plug from the front side using your suggestion of a paper clip and got nothing. To verify the use of the clip I used it on the front side of the prior white wire and still got 13.4

Then I crawled behind the heater and pulled the yellow from the relay then I crawled under the coach to test the yellow wire with red on the wire opening and black on the metal cabinet containing the water heater
Got 0 again

If I did reattach the ground wire and the relay wire back to the tank the element cover containing the relay and all the other wires is too tight to the tank to be able to access the inside of the shell to do any tests on the relay

So I am hoping that the yellow test is valid and we have isolated the problem between the first and second connector on the control board which I assume means a bad board?

Advise your thoughts.

Seems to me that this is such a complicated way to simply supply 120 volt power to an element
Or
Is there more to this control board?

Is there a bypass that a novice like me could accomplish? or if we agree that the board is bad is it best to get replacement?

Sam

Samflhomes 07-21-2015 06:03 PM

Just for grins I replaced the two amp fuse in control board but made no difference Still no voltage on lower connector that hold yellow wire
Still 13.4 volts on upper connector containing the white wire

Gas flame still turns on when I flip gas switch in coach

Depending on what you Advise I will reconnect all wires at back of heater tomorrow and go to next step

ShapeShifter 07-21-2015 08:56 PM

Looks like we're making some progress!

Quote:

Originally Posted by Samflhomes (Post 2660323)
Just for grins I replaced the two amp fuse in control board but made no difference

Good idea! Too bad it made no difference. :sad:

Quote:

Still 13.4 volts on upper connector containing the white wire
That's a very good sign. It means the coach's wiring, fuse, and control switch are good, the problem must be in the water heater somewhere.

Quote:

Gas flame still turns on when I flip gas switch in coach
Good, the water is cold enough to be calling for heat.

Quote:

Still no voltage on lower connector that hold yellow wire
Bummer. Well, it looks like we found the problem, it's somewhere between the white wire and the yellow wire.

Just to be sure: when you measured the voltage on the yellow wire, the connector was still plugged into the control board, right? If not, it's not a valid test as the power is coming from the control board and we would expect the yellow wire to be dead if it were unplugged. Are you SURE the meter probe was actually touching the contact? I see you used the same method with the white wire, are you sure you used the same technique?

Some more things to try, now that it's narrowed down:

First, turn off the electric and gas water heater control switches.

Unplug the upper connector from the control board (the one with the white wire. Look in the connector, the side that mates with the control board. Do all of the contact fingers (especially the white wire) look good? Nothing burned, corroded, or bent out of position?

Look at the control board's contacts: they are a set of metal fingers printed on one side of the green fiberglass board sticking out of the black epoxy potting compound - the spring loaded fingers of the white connector press against these copper patches on the green board. Do all of the fingers look clean and shiny and not burnt? You can use an eraser on the end of a pencil to polish them up.

Now do the same with connector with the yellow wire: all of the connector fingers look good? All of the contacts on the control board look good?

After inspecting and cleaning the contacts, plug the connectors back in and repeat the measurements: turn on the electric heat switch, does the white wire still have power? (It had better!) Now, with the switch still on, measure the yellow wire. Does it now have power? If so, it was probably bad contacts: put everything back together (including the back of the water heater) and test it, and hope it now works. If the yellow wire still doesn't have power, it looks like it's a bad control board.

You had some questions in your previous post:

Quote:

Originally Posted by Samflhomes (Post 2660260)
(For clarification I turned meter on to DCV and was surprised to see number Ike 65.7 etc but when I grounded the black lead to the relief valve and put the red on the white lead I got 13.4)

You have an auto-ranging meter. That means that it is constantly adjusting the sensitivity of the meter according to the voltage you are measuring. When you don't have it on any voltage, or are measuring a very low voltage, it adjusts to a very sensitive scale. When you are measuring a higher voltage, it may take a couple seconds, but it will adjust itself to a less sensitive scale. If you look closely at the display, there should be a small indicator with some letters to tell you the scale.

When you didn't have the meter probes connected to anything, it adjusted to its most sensitive scale, which probably gives a maximum reading of 200 mV (thousandth's of a volt, or 0.200 V.) When the meter showed the number like 65.7, it probably had the mV indicator lit, meaning it was reading 0.0657 volts. That's practically nothing, it was just picking up electrical fields in the air. This is normal.

When you did connect to the white wire, the 13.4 volts was much more than the 200 mV, so it probably flashed an overload indication. The meter then adjusted the sensitivity to a 2V scale, still to much. It then went to a 20V scale, and this time it got a good reading of 13.4 volts. At this point, the indicator on the display should've read V, not mV.

This auto ranging lets it get a good reading at higher voltages, while still having enough sensitivity to measure very low voltages.

Quote:

So I am hoping that the yellow test is valid and we have isolated the problem between the first and second connector on the control board which I assume means a bad board?
Yes, I think the additional yellow wire tests you did were valid. Assuming that cleaning the contacts above didn't fix anything, it's really looking like a bad control board.

Do you know anyone with the same model water heater? An interesting test before buying a new board would be to pull the board from your water heater, and temporarily plug it into a different water heater. If the electric element now doesn't work on that water heater, you definitely have a bad board. But if it does work, we've got to go back to the drawing board to find a really strange problem.

Quote:

Seems to me that this is such a complicated way to simply supply 120 volt power to an element
Actually, I think it's a pretty good way. You run a simple low voltage control signal, and plug the water heater into a regular old unswitched power outlet. The wiring is very simple, and the control elements are all right there at the water heater.

There are two alternatives: Run the AC power through a regular wall switch, and then to the water heater. The downside there is that because of electrical codes, you can't put that switch in the same control panel with the other low voltage switches, the wiring for a 120V switch must be isolated by putting it in a separate box, or putting dividing walls in the box behind the control panel. That adds complexity and doesn't really simplify the water heater wiring or controls, because the water heater still needs a relay or separate thermostat and limit switch to turn off the current to the heater when the water is hot enough.

Or, you keep the low voltage switch in the control panel, run that to an external relay, and then run the switched power to the water heater. But you still need the relay or separate thermostat and limit switch at the water heater. This was what the setup was with the last water heater YC1 and I helped with, and it was a struggle finding that extra relay hidden in the coach and figuring out the proper wiring for it.

Quote:

Is there more to this control board?
By running the control signal through the control board, it simplifies the wiring in the coach, and also simplifies the wiring in the water heater because a single thermostat and limit switch can be used to control both heat sources, and a single power relay controls the power to the element for both heat control and on/off functions. The logic and circuitry to do that are all on the control board.

Unfortunately, all of the interesting parts of the control board are sealed in epoxy. They obviously don't intend you to service or repair the board. Other than replacing the fuse, and cleaning the contact, there isn't much you can do besides replace the board.

Quote:

Is there a bypass that a novice like me could accomplish?
I would NOT recommend a bypass. You could make the heating element come on by jumping the white and yellow wires, but then you would have strictly manual control of the heater. This would be very dangerous because if you left the switch on, it would be constantly heating, and would quickly reach dangerous levels, even going so far as to be boiling the water and generating steam. Very dangerous, don't do it!

You best bypass at this point is to just run it on propane.

Quote:

or if we agree that the board is bad is it best to get replacement?
It sure looks like the control board, and getting a replacement is probably the solution, unless you have a friend you can temporarily swap with to test it as described above.

I'm out of ideas: does anybody else have any tests they can think of to prove or disprove the control board theory? Myron?

Samflhomes 07-21-2015 09:39 PM

Well Shape Shifter as a former systems developer I knew from your other posts that you could train me with detailed instructions

I now know how to use a multimeter which I have avoided for years
And how to diagnose a water heater . I am quite sure I did the tests as you instructed and apparently you see no issue in my failed test of yellow that is caused because I have not yet reconnected the green two black and white wire to the back of the tank?

You and others on this site are a tremendous help and I can't thank you enough. I can only strive to help others as payment.

However we are not done yet

Your idea of swapping boards is great but the only person I know that has the same model is YOU but I don't think we can swap through the mail.

I see a circuit board on Amazon for $135.40 plus shipping and tax part number 91226 that has been replaced by 93851

However before I order that board would you agree that just as a test for only a few minutes THAT you could tell me a simple way I could create a jumper from the white to yellow just to confirm that the yellow wire, the relay and Element do their Job and the heater starts drawing 11 amps on my portable EMS DISPLAY? I understand I can't leave it bypassed for more than a short period.

Is that too risky since I am bypassing whatever safety and control features that the circuit board provides during electric heating of water. I would not want the bypass to destroy the relay or some other unintended consequence

Perhaps it could be jumped from the little holes in the top of the connector?

I gather from your comments that there is no trick to replacing the circuit board? Just remove three connectors and mount new board?

Thanks again for shepherding me through this so far and not causing more problems for myself as has been forewarned

Sam

Samflhomes 07-22-2015 12:05 AM

Just to be through I will reconnect the 4 wires to the back of the heater and verify that there is still no power at the yellow wire on the bottom connector on the circuit board

ShapeShifter 07-22-2015 06:12 AM

Quote:

Originally Posted by Samflhomes (Post 2660675)
I am quite sure I did the tests as you instructed and apparently you see no issue in my failed test of yellow that is caused because I have not yet reconnected the green two black and white wire to the back of the tank?

Not having the relay's green wire connected at the back of the water heater will not affect the voltage that is measured at the control panel. It is still a valid test.

But not having it connected will prevent current from flowing and will prevent the relay from actually controlling the heating element. So it can't be left that way, which I'm sure is no surprise.

Quote:

Your idea of swapping boards is great but the only person I know that has the same model is YOU but I don't think we can swap through the mail.
If we were local to each other, I'd be happy to swap for testing purposes. But doing so through the mail is not really practical: it will take time, during which your water heater will be down, and it just increases the total repair costs by adding more shipping charges.

Quote:

However before I order that board would you agree that just as a test for only a few minutes THAT you could tell me a simple way I could create a jumper from the white to yellow just to confirm that the yellow wire, the relay and Element do their Job and the heater starts drawing 11 amps on my portable EMS DISPLAY? I understand I can't leave it bypassed for more than a short period.
Yes, I suppose that is a reasonable temporary test. But first, did you check and clean the contacts as suggested last night?

Turn off the control switch and AC breaker power, then properly reassemble everything behind the heater. Unplug the two connectors from the control board. Straighten a paper clip and insert it in the holes in the back of the connectors, jumping from the smaller connector's white wire, to the larger connector's yellow wire. Make sure nothing can short out to anything else. Now, turn on the AC breaker, and flip the control switch back and forth: you should be able to hear faint clicks from the relay, and you should see the current draw change by approximately 11 amps. Do not leave it bypassed for any length of time.

This test completely removes the control board from the circuit, but uses every other part of the AC heater control system. It doesn't test the thermostat or other control logic, but we already know those parts work because the propane half of the system is working properly.

If this test works, then it would seem to be the control board, as every other significant part is tested. If the heater doesn't draw current with this test, then there is still an issue somewhere - were the relay connections properly assembled?

Quote:

I gather from your comments that there is no trick to replacing the circuit board? Just remove three connectors and mount new board?

That should be all it takes.

YC1 07-22-2015 07:58 AM

Use a couple of those plastic thumb tacks to pierce the wires or some sewing pins to make a quick jumper.

Samflhomes 07-22-2015 11:31 AM

This experiment was successful
I used a large paper clip to jump from top white to bottom connector yellow

Lots of clicking noise do turned on breaker and 11 amp draw

So it's the circuit board

I'll look closely at the connections again but if no luck there I guess I have to buy a board

Thanks for the tremendous help

Sam

Samflhomes 07-22-2015 11:57 AM

I checked the wires going into the circuit board for any possible shorts that may have fried the circuit board
I don't want to ruin the replacement

Only thing I saw was brown wire with thermal fuse has some damage from touching chimney metal but no visible bare wire. I re routed this and will tie wrap all wires

Cleaned connections but still no power to the yellow wire

So I am going to put cover on element that contains the relay then rebolt the cover plate behind the water heater. Oh my aching back

Then order a circuit board

Sam


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