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Old 07-19-2015, 12:59 PM   #1
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No power to water heater element

Element checks good at 10.4 Ohms
But no voltage at element

Gas heater works fine but not electric

Have been told that inside switch is 12 volt that must have a in line relay somewhere that turns on 120 volt

That Relay may be bad

How do I find that relay?

Or other suggestions

Sam
2004 Seabreeze LX WH
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Old 07-19-2015, 01:27 PM   #2
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I had this issue with my Bounder a couple of years ago. On my Bounder there is a 12 vdc relay at the back of the water heater that controls the 120 vac. The 12 vdc for the relay has a fuse in the coach 12 vdc fuse panel and is controlled by the water heater on/off switch. The 120 vac power for the heater element comes from a circuit breaker in the cb panel and is controlled by a relay in the Electrical Management System, EMS. This is a load shed system used to trip circuits if the coach is drawing to much power. I don't know if you have this system or not. My problem was the EMS. Hope this helps, good luck.
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Old 07-19-2015, 03:13 PM   #3
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I do have a progressive EMS
But it shows no errors

No Amps on EMS on leg one just on leg two

Maybe the fuse blew now where is that located?

Sam
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Old 07-19-2015, 03:31 PM   #4
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Mine did not show any errors either. But the relay contacts on the EMS circuit board for the water heater were open. Probably burned open due to applying/removing power to the coach with the water heater switch on one to many times.
I saw in one of your pictures on another post what looks like the 12 vdc relay at the back of your water heater. Check for 12 vdc and 120 vac at the relay. Check for 120 vac thru the relay to the heater element with the water heater switch on. If the relay is good and no 120 vac at the relay check the 120 vac circuit breaker and the EMS.
I just realized we may be talking about two different EMS's. I am not referring to a surge protector type EMS that we add to our coaches. I am referring to a load shed system that is built into your coach at the factory that trips individual ac circuits in the event of an overload. Mine trips the water heater first.
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Old 07-19-2015, 05:01 PM   #5
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Redcolorado
Yes mine is a surge protector at the plug not intigrated with rv

Your suggestions to check DC and AC current at relay sound right except I am a complete novice and don't know how to go about doing that check

I was able to use digital meter on the element and no power but I don't know where to use the black and red (positive) probes when checking the several wires attached to the relay which is inside a plastic cover that goes on top of the element and a little difficult to work on from under the coach reaching high up while on my back
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Old 07-19-2015, 05:25 PM   #6
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FWIW even if you do not have an automatic load shedding system you should have a manual switch for the 12 VDC to the relay.
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Old 07-19-2015, 05:44 PM   #7
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I do have a manual switch
Whatever point that makes?

All I know is that there is no power to the element and the element checks good from white to black side at 10.4 ohms and there is no ohms when checking black side of element to the tank (ground)

I need to learn how to check AC current to the circuit board and to the relay that connects to the element

Again I have a working gas side just no electric

Sam
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Old 07-19-2015, 07:21 PM   #8
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What make/model is your water heater?

If it is a Suburban, there are two high heat reset buttons under the black rubber cover. One for electric and one for gas.


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Old 07-19-2015, 10:23 PM   #9
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My heater is a an Atwood 10 gallon combo gas electric model 4e

There is an Eco in front but not sure how to check its affect on lack of power to my heating ElementClick image for larger version

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Old 07-19-2015, 10:24 PM   #10
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There is a RELAY at rear of heater within the element plastic cover
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Old 07-20-2015, 07:43 AM   #11
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Quote:
Originally Posted by Samflhomes View Post
Element checks good at 10.4 Ohms
But no voltage at element

Gas heater works fine but not electric

Have been told that inside switch is 12 volt that must have a in line relay somewhere that turns on 120 volt

That Relay may be bad

How do I find that relay?

Or other suggestions

Sam
2004 Seabreeze LX WH

Here is the Service Manual http://manuals.adventurerv.net/Atwoo...er-Service.pdf

Page 25 shows the schematic. The ECO is just a closed switch is common to both propane and electric. Since propane works, it is ok. Your problem is more likely the relay which you should be able to verify with a volt meter.


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Old 07-20-2015, 07:55 AM   #12
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Quote:
Originally Posted by Samflhomes View Post
My heater is a an Atwood 10 gallon combo gas electric model 4e
What is the exact model number from the rating plate inside the outside door? That will make a big difference.

From the pictures you've posted so far in this thread and your other other thread, it looks very much like my own Atwood GC10A-4E heater. The following is assuming that this is true, my statements may not be correct if you have a different model.

You measured 10.4 ohms on the electric element, so it is likely good. To be absolutely sure, you should take two more measurements: with the meter still in Ohms mode, and both wires disconnected from the heater, measure from each terminal of the heater to ground (the metal of the tank.) Both of them should read very high resistance (probably an "OL", "OV" or other error indication on the meter.) If so, the element is good. If either terminal reads low resistance to ground, the element is shorted to ground internally and will need to be replaced (this is unlikely.)

A big clue is that it is still working on gas. If you have the same model as I do, then you can rule out the thermostat, high limit switch, thermal fuse, and most of the control board. The same controls (thermostat, high lmiit, etc) operate both the the gas and electric side of the heater. So if gas is working, electric should also. The ECO is only used on the gas side.

With gas working, that leaves the electric control side:



For the following measurements, set your meter to measure DC volts using the DCV switch position, and the leads in the center and right sockets. Keep the black lead (from the center meter socket) on a good ground (clean exposed metal on the MH frame or water tank - like the body of the pressure relief valve.) Touch the red lead (from the right meter socket) to the points to be tested. Where I say 12V in the following steps, it's actually whatever your battery voltage happens to be which could be anywhere from a little below 12V to over 13V. Any reading like that is good.

The inside control switch should be 12V, and should provide 12V on the white wire going to the control board: 12V when the switch is on, nothing when the switch is off. If you don't get anything in either switch position, the switch is bad or there is a blown fuse or broken wire somewhere in the path between the battery and the water heater. I can't give you specific advice since the details depend heavily on the coach's make, model, and year, and I have no experience with your coach.

If that is working so far, the yellow wire coming from the control board controls the relay on the back of the water heater. If the control switch is on, and the water is cold, there should be 12V on that wire. If the control switch is off, or the water is already hot, there should be no voltage on the yellow wire. If either of these statements is false, there is a problem on the control board, or a bad connection where these wires attach to the control board.

Next, check the voltage at the back of the water heater. First, turn OFF the circuit breaker for the water heater, we don't want any high voltage back there while making these measurements! With 12V present on the yellow wire (from the previous step) measure the relay contact that has the yellow wire. It should also be 12V. If not, there is a break or bad connection in the yellow wire. Now, check the other low voltage wire terminal of the relay, this is the wire (black?) that goes to the ground screw on the back of the heater, not the wires that go to the element or power cord. That should not read any significant voltage: if it does, that wire is broken or has a bad connection.

As a final test, while you are looking at the relay, have someone flip the electric control switch on and off, you should be able to hear some soft clicking from the relay as it switches. Now, with the AC breaker still off, and the meter set to measure resistance again, measure the resistance of the two relay terminals where the high voltage wires to the element and power cord attach. With the control switch off, they should read high resistance. With the control switch on and the water cold, they should read very low resistance. If they always read high resistance, the relay contacts are bad and the relay must be replaced.

If all is good so far, the low voltage controls are good, and it's time to work on the high voltage side. Turn on the AC breaker to the water heater, set the meter to ACV, and be very careful! There are now dangerous voltages present at the back of the water heater, do not accidentally touch or short any exposed wires!

There should be a black and a white wire coming in to the relay box from the power cord. Black goes to the relay, white to the heating element. Measure across these two terminals, and you should see about 120 volts. If so, you have a break in the wires somewhere in this relay box. The circuit is quite simple: power comes in on the black lead, goes through the relay contacts (already determined good in the previous step) then through the heating element, and out the white wire. With everything connected up, and 120V coming in the black and white wires, there should be 120V on the heating element when the control switch is on and the water is cold, and no voltage on the heating element while the control switch is off or the water is hot.

If you aren't getting 120V on the white/black wires of the incoming power cord, then the problem is in the coach wiring. Your water heater might be hard-wired into the coach, or it might have a cord with a regular three prong plug plugged into a regular AC outlet behind the water heater. From there, it may go through any number of junction boxes as it works its way back to the breaker panel. If you open up the cover of the breaker panel (be very careful, there is high voltage and high current in there with lots of exposed wiring points!) you should be able to measure 120V between the output screw of the breaker and the bus bar where all of the white wires connect. If not, you have a bad breaker.

If you do have power on the output screw of the breaker, but not coming in the power cord at the back of the heater, then you have a break in the circuit somewhere between the two. I can't offer any specific advice there because the way the wires are routed and connected vary widely between different makes, models, and years of coaches.

You mention you have a Progressive EMS. As long as you have ANYTHING in the coach that is working properly on AC power (like the air conditioners, but not including things on an inverter) then the problem is likely not there. If you have power on the output screw of the water heater's circuit breaker, it is definitely not a problem with the EMS.

However, there are two types of EMS systems. Many coaches have a load shedding EMS that will turn off certain non-critical circuits if too much power is being used from the shore cord. On my coach, I also have an Intellitec EMS built into the breaker panel, and one of the loads that can be shed is the water heater. Do you have a system such as that? If so, what is the exact make and model number? Can you verify that it is not trying to shed the AC power to the water heater?

Good luck!
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Old 07-20-2015, 10:53 PM   #13
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Shape shifter thank you for coming to my call for help

I won't be able to get back to this until tomorrow after noon at the earliest

Although you have detailed instructions I still have questions due to my inexperience using a meter

First I want you to know we have the same model and that my EMS is a portable that I add at the post when I plug in at rv for park.

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

Then I did test for AC voltage and there was none. 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.

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?

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. However does it matter that all the 4 wires described above are still not attached to the rear of the tank?

So when I get to the relay I need to find a good ground with the black and touch the yellow in the relay

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.

I don't know how to identify the power cord attachment to the relay since I don't know where the power cord is but I am sure I can identify the other black wire that goes to the element. When you say high resistance is that the ol again? What is very low resistance on the meter look like? Need to know the digital value you are implying.

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.

If you can answer these question i feel more confident with my measurements especially with the back side of heater

Thank you so so much
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Old 07-20-2015, 11:07 PM   #14
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Photo of the relayClick image for larger version

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Ill use phone and reach up past the element to see if I can get photo of the various wires that are joined together with wire nuts. This is probably the power cord you Are referring to but as I recall there are about 4 sets of wire nuts being used which seems like a lot for just power cord
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