Rear A/C

[66gt350]

Hi everyone. I was out in my motor home this morning and turned both heat pumps on. Yes I'm plugged into a 50 amp source. Both H/P units ran for awhile and then (I think) both units slowed down very badly. I turned them off and tried them a little while later and only the front unit comes on. Rear unit doesn't have any power to the junction box inside. After switching all the breakers off and back on then neither H/P runs and the EMS panel is not displaying the lights that show what loads can be run. If I go to generator all the lights will display. If I turn the washer/drier CB off it will go to 30 amps and display the way it should. I know it won't display amp draw when on 50 amps but it always showed the load lights, Everything seems to work except the 2 H/Ps. The temperature outside is about 40 degrees. Could that have anything to do with the H/Ps not coming on although that wouldn't have anything to do with the lights.

[Timaz]

check the voltage at your 50 plug

[windsorbill]

Even if the temp is 40, the heat pumps should run, they may not heat very well, however.

If your coach is like mine, you have a multiplex system. I'd check the fuse directly on the circuit board. Your circuit board may be toast, or at least the relays on the board. Mine is in the back closet, in same box as the circuit breakers. The heat got to it over the years. I just replaced it last summer from M&M Electronics.

From your post also, I'm assuming the roof units will not work with the generator either, is that correct?

[96 Wideglide]

Originally Posted by windsorbill

From your post also, I'm assuming the roof units will not work with the generator either, is that correct?

First thing I'd check.

[66gt350]

I didn't check for the H/Ps running on the generator,but will check that on Friday. (Can't tomorrow,Turkey Day!!!)
Bill, is there any kind of test for the circuit board? Do you have a contact for M&M Electronics?

Timaz. I did check for 50 Amps and everything is good there. I have a Progressive surge protector and that is showing voltage on both sides with no errors.

I'm trying to get everything in order to head out to Quartszite right after Christmas.

Thanks everyone
Jim

[Windecker]

Yes, trying generator is a great idea.

If you have the portable version of the Progressive surge protector, take that off and try it (if the gen works the system OK) as I have seen others have issues with them. Not wide spread failures but have heard of it.

Sure hope it is easy to track down.

One thing for sure, the Heat Pumps run straight off of Generator or shore power so the inverter portion should be no factor.

Also have seen a few plugs burn one leg off at the connector so you wind up with either 1/2 power or failed neutral which causes all kinds of issues.

So back to testing with the generator, knocks most of the above out if it all still does not work. Then the multiplex control becomes more of an issue.

Windecker

Originally Posted by 66gt350

I didn't check for the H/Ps running on the generator,but will check that on Friday. (Can't tomorrow,Turkey Day!!!)
Bill, is there any kind of test for the circuit board? Do you have a contact for M&M Electronics?

Timaz. I did check for 50 Amps and everything is good there. I have a Progressive surge protector and that is showing voltage on both sides with no errors.

I'm trying to get everything in order to head out to Quartszite right after Christmas.

Thanks everyone
Jim

[96 Wideglide]

Well, if the HP's, and everything else works fine on gen power, I'd look at the transfer switch first. May even just be a loose connection on the shore power side.

[nodine]

Originally Posted by 66gt350

Hi everyone. I was out in my motor home this morning and turned both heat pumps on. Yes I'm plugged into a 50 amp source. Both H/P units ran for awhile and then (I think) both units slowed down very badly. I turned them off and tried them a little while later and only the front unit comes on. Rear unit doesn't have any power to the junction box inside. After switching all the breakers off and back on then neither H/P runs and the EMS panel is not displaying the lights that show what loads can be run. If I go to generator all the lights will display. If I turn the washer/drier CB off it will go to 30 amps and display the way it should. I know it won't display amp draw when on 50 amps but it always showed the load lights, Everything seems to work except the 2 H/Ps. The temperature outside is about 40 degrees. Could that have anything to do with the H/Ps not coming on although that wouldn't have anything to do with the lights.

The Energy Management System (EMS) is notorious for causing problems with the rear air conditioner/heat pump. We had that problem several times and finally put a jumper across the shedding relay on the circuit board. I am quite capable of managing my own power loads.

Bob

[jacwjames]

Do any of the other things work with the EMS, washer/dryer or the water heater??


There is a reset procedure for the EMS system, basically have to remove all power, there is a small fuse on the side of the panel that takes the 12 volt off. Leave power off for ~10 minutes and then try again.



here is a link to a manual if you don't have
https://janeandjohn.org/docs/EMSmanual.pdf


M&M Electronics link
https://www.mmrvelectronics.com/


My EMS got hit by lightening. I did the troubleshooting to determine this and then called M&M who who had me do the above to try and reset, no go. I ended up ordering a new board but since my model was obsolete I had to upgrade meaning a new load sensor and wiring harnesses, not a bad install but the instructions were not that good. Cost ~$450 about 4 years ago.



I did bypass the EMS in order to be able to run the AC's while waiting on he new board. Easy to do, just mark the wires.

[windsorbill]

Originally Posted by 66gt350

I didn't check for the H/Ps running on the generator,but will check that on Friday. (Can't tomorrow,Turkey Day!!!)
Bill, is there any kind of test for the circuit board? Do you have a contact for M&M Electronics?

Timaz. I did check for 50 Amps and everything is good there. I have a Progressive surge protector and that is showing voltage on both sides with no errors.

I'm trying to get everything in order to head out to Quartszite right after Christmas.

Thanks everyone
Jim

M&M (419) 965-3014 They are very helpful. There is no test that I'm aware of that an owner could do. Be sure you have the model number handy for the multiplex. I think the board was in the $250 range, shipped to me. Very easy to swap it out.

But before you do that, check to see if genny will run the a/c units. Completely unplug the shore power just to be sure there's not a transfer switch issue.

Maybe I'll see you in Quartzsite.

[66gt350]

Okay, I got a chance to do some testing today. With the genny running everything worked except the rear H/P. I reset everything and nothing changed. I disconnected and reconnected the push on connectors on the circuit board and everything came back except the rear H/P.

Does everyone still think it's the module??

Bob; what wires do you jump to bypass the EMS. I would like to fix this but would like a back up plan if needed.

Thanks all
Jim

[windsorbill]

Originally Posted by 66gt350

Okay, I got a chance to do some testing today. With the genny running everything worked except the rear H/P. I reset everything and nothing changed. I disconnected and reconnected the push on connectors on the circuit board and everything came back except the rear H/P.

Does everyone still think it's the module??

Bob; what wires do you jump to bypass the EMS. I would like to fix this but would like a back up plan if needed.

Thanks all
Jim

I jumped mine a few years ago. Notice the 2 wires on the same terminal. (black and yellow) Like Bob, I managed my own loads and everything was fine. A few years later, all the lights in the coach would randomly turn off and on, as if it was haunted. That forced me to replace the entire control board last spring. everything good now.

[96 Wideglide]

Could be a blown run capacitor on your rear HP.

When one of my start capacitors went, the compressor would try to start every minute or so, and the amp draw would go way up for a couple of seconds. Wonder if that is what you were see'ing when both of your HP's appeared to slow down.

Just a thought.

[nodine]

Originally Posted by 66gt350

Okay, I got a chance to do some testing today. With the genny running everything worked except the rear H/P. I reset everything and nothing changed. I disconnected and reconnected the push on connectors on the circuit board and everything came back except the rear H/P.

Does everyone still think it's the module??

Bob; what wires do you jump to bypass the EMS. I would like to fix this but would like a back up plan if needed.

Thanks all
Jim

Jim,

Pull off the AC distribution panel cover. You should have a dedicated 20 Amp circuit breaker in the panel for the rear air conditioner. Follow the output of that circuit breaker over to the EMS circuit board. That wire is connected to a terminal that leads to one side of the shedding relay for the rear air conditioner. The next wire on the terminal is the output of that relay and travels to the rear air conditioner. Take a voltmeter (on the AC range) and check that you have power on the terminal coming from the 20 amp circuit breaker and that you do not have power on the the other terminal. That will verify that the relay has failed and you can just move that wire from the output terminal to the terminal that comes from the 20 amp circuit breaker. You will have two wires in the same terminal. Before doing this make sure you turn off all the breakers supplying power to the EMS. There should be four of them, Front AC, Rear AC, Water Heater, and Wash/Dryer. Or you could just throw the main breaker. At any rate play it safe. Once the wire is moved to the input side of the shedding relay you can turn all the breakers back on. If there was power on both sides of the rely when you used the voltmeter to test the circuit then the rely is not the problem and something else is wrong.

While you have the power off you need to tighten up all the terminals on the EMS board. I do this once a year on the EMS board, as well as all the terminals in the distribution panel and the transfer switch. These connections can loosen over time and cause the terminals to heat up. Both the EMS board and the transfer switch have been known to fail from over heating. The transfer switch has even caught on fire. Be sure all the power is removed from the coach and the breaker on the generator is turned off before doing this. I always turn off the breaker on the generator just to make sure the Auto Gen Start does not fire up the generator while I am working.

Good luck,

Bob