AC and Heat Issues

[Supertommy68]

My RV Comfort T stat is non responsive. Thought it was a bad stat. Replaced it and issue persists. Where do I start troubleshooting?

[chuckster57]

That’s a Coleman thermostat, they have a fuse. Even with a new thermostat, I would check the fuse. After that it’s time to check for 12V to it. Look at the control box in the AC unit it’s connected to.

[Supertommy68]

I did check fuses all were good. I have 3 ac units any suggestions where the control boxes would be? They are not in the basement I checked.

[chuckster57]

3 AC units and a single thermostat?

[Supertommy68]

Yes it is 3 units rooftop and 1 gas furnace. The instructions for the thermostat say it can operate up to four units. It doesn’t make any sense that none of them would be responding. The instructions also show separate control boxes for each unit for a generic installation, but I’ve no idea where to find them. I took apart the basement wall panels trying to find a hidey-hole somewhere but nothing. It seems convenient that all of them would go bad at the same time. There has to be one central brain somewhere that operates all of them. And it apparently is not the thermostat.
I don’t know if this would affect it or not, but I did have generator service last week. They had to remove and reinstall the generator under warranty, because the rotor stopped working. Again, I don’t see how that affects anything but could it?

[chuckster57]

If the AC units are on the roof, the control boxes should be in the return duct. IF you have ceiling plenums then just remove the ceiling panels. If you have the "whisper quiet" system then you have to take the cover off on the roof and then take the front cover assembly off.

This may or may not help:

https://airxcel.com/coleman-mach/service-support/document-library

[Rinsrig]

The control unit is in the AC unit itself. If you pull the cover off the top of the unit (from the roof top) each of your units has a set of dip switches that tell the system which unit is which zone. Nothing will work unless there is 12 volts to the thermostat, the power is NOT supplied by the AC units. You will need to make certain that you have 12 volt power coming into the back of the thermostat. Most thermostats will show a display and look like it should be working, but without that 12 volts, nothing will happen.

[Supertommy68]

I have a main battery total kill switch/disconnect. When off, there is no display on the t stat. As soon as I turn the switch on, the display on the t stat comes on. I have to believe it is getting 12v, unless there are two 12v inputs for it, but the instructions don’t indicate that. When I switched stats yesterday to “test”, I hooked up the new one exactly as the factory did it on the existing one. That wiring setup seemed to work till this weekend.

[K_N_L]

Not sure which brand you RV is but on mine , from the factory, with 2 ac's and the t-stat on the wall beside the stairs, the wiring for the t-stat ran first to the bedroom unit then to the main living area. The units are daisy-chained together and as noted, unit numbers are set by dip switches. Again on my Fuzion, while ducted, the control units are accessible by removing the inside panels, 8 square drive screws, 4 for the external and 4 for the internal panel, and it should expose the control box and the t-stat wiring. Might as simple as a bad connection on the control board due to travel bouncing.

[Supertommy68]

K_N_L—
I have a raptor 398. I’ll have to wAit till the weekend to work on it again. Neighborhood association doesn’t like RV’s parked outside. Your suggestion then is to figure out which AC unit is first in line, probably the bedroom, and go from there? I’ll try that. Makes sense but still don’t know why the furnace heat would not work. Seems there needs to be a brain somewhere that controls it all. I did look at the “in command” control board but there is nothing on there listed for AC or heat. There was only one wire coming from it to the t stat ( at least that I could tell).

[K_N_L]

Here is a link to a good overall diagram of how it should be connected in a multizone system - figure 5 on page 10 of the pdf.



https://www.rvupgradestore.com/v/vspfiles/assets/pdf/9330f4552.pdf


I misspoke it is a pin jumper not a dip switch on the control unit in case anyone is checking up. I only know this as I converted my 3rd unit from control knobs on the unit to t-stat control after having the g-kids turn it on and off, and on and off, if you know what I mean. Love them but getting older and the patience can get short. I swapped out the control box, ran t-stat wires between the central and garage units, I didnt have to actually do any changes to the thermostat.

[DHred]

Our 17 Fuzion has a similar problem. I've noticed if the 1 and 2 are not showing on the thermostat active zones that zone or both zones will not work. On our unit the problem is a signal wire connection up in the living room ac unit. I remove the inside grill and wiggle the 2 signal wires and things will work again. I replaced the connector once but it still gives trouble. I'm considering converting the bedroom ac to manual control for the safety of our dogs while we are gone.

[Supertommy68]

DHred-
So this morning, I pull the living room HVAC cover and bingo, the 12v red wire is loose. I almost paid a mobile rv repair guy to troubleshoot this problem- so glad I saved the money. So on the Raptor 398, the tstat wire to the AC units goes to the living room AC first, then branches to the other 2. All three get connected together to the LR AC control board. Well, the main (red wire) from the tstat was the one that was loose, and caused all of the issues I was having. I decided to redo all of the connections, with shrink tubing and new connectors, on all three AC units, and on the T-stat.
Also, on the 398, the relay that allows only 2 AC's at a time is located behind the main panel under the pantry. I pulled that out and hooked the rear AC to the dryer breaker, since I know I will never get a dryer. Now all 3 are running, off 50Amp shore of course. Stoked for sure!! I haven't tried to run all of the genset yet, and probably won't attempt it. The rear AC breaker will stay off unless I'm on shore.
I was going to hook up the heat strip in the garage, a mod I have seen posted elsewhere in the forum, but the unit I have does not have that capability that I could tell. Thanks all for your help!!

[K_N_L]

Glad to here that you got it working. Someone (dont recall who) mentioned that Raptor and Carbon are build in one facility and Fuzion / Impact another and that kinda makes sense that there would be some differences. Nice find / fix!

[Tommysmith]

Does it have the "In-Command" system? If so and the heat inside exceeds 100 degrees, or below 40 deg, it won't work....

[Frosty46]

First verify you have the 12 volt dc supply to your avc/heat system. This is best done at the t-stat as it's easy to expose the terminals there. If you have no 12 volts the entire system will not function. Let us know what you find out.

[Dusty]

Does it have the "In-Command" system? If so and the heat inside exceeds 100 degrees, or below 40 deg, it won't work....

Not all In-Command systems have this problem. Mine built 3/19 works fine above 100 degrees. The older In-Command units have a fix for the issue.