Coleman-Mach Heat Pump Problem 2004 Itasca Horizon 36GD

[Kim Petersen]

Hey all,
I have a 2004 Itasca Horizon by Winnebago 36gd, cat L6 motor allison 6 spd.

yesterday evening we came home to find the thermostat on the information panel display ER. would not let me turn the heat pump on, or the gas furnace. temp was in the mid 50's F.
the temp here in sw Az. have been in the 40's overnight so haven't used gas heat for a while. but now nothing will heat up except our portable electric heater.
I removed the T-stat, unhooked the wires and let it sit a spell, hoping it would reset, but that failed.

any ideas?

 

[Morich]

I think this will be a function of the thermostat. Do you have the info on what brand and model of stat you have?
I would suggest that there is likely to be online manuals available and by finding the correct one, you may find the correct procedure to reset the lockout if that is actually the problem.
I normally think of lockout being a result of the thermostat trying to bring things online but failing for some reason.
That may mean it takes a bit of looking at what may have caused the basic problem of not firing the furnace?
But that is very much theory and may not be the case at all!
But with about a billion different combos, starting with the correct info for what you have is likely to be needed as a first step!
What we often have is the furnace is one, the air is another and the thermostat is yet another builder, so getting the right info is difficult at times as there doesn't seem to be full agreement on things like colors of wires, etc.

If you post up the brand of thermostat you have, somebody may pop in and know the rest procedure?

 

[powercat_ras]

The propane furnace and Heat Pump/AC units only take signals FROM the thermostat. There are 4 signal wires that go from the thermostat to the Heat Pump AC and 1 signal wire that goes to the propane furnace.

I'd try power cycling the thermostat either and see if it resets.

 

[Morich]

But then , there may be some questions to ask?
Is there reason to think it is the thermostat and it needs reset or is that a leap too far?
Looking at that thermostat as really just a switch, one of the big issues is that switch has to have power getting to it before it can switch it on through!

Any checks on the breaker, etc. getting power to the thermostat for it to work?
Maybe a quick check here if not been done before?

If the breaker is good, there may be a number of connections between it and the thermostat and some of them may need checked.
There are a couple places where these might be checked being open if the breaker is good. Also the ground has to be good at both stat and furnace, so check that as well!


Not sure of what you have looked over yet but I might mention some things which could confuse??
The wires you see at the thermostat are often soldered to it and then go down into the wall to meet the wires that Winnebago adds. So you may need to gently tug those wires up out of the wall to get to that connection. And that is where you may find wire ID stamped on the ends of the Winnebago wires as ID for each wire.


What this tells us is that 12VDC should be coming to the plug at the front thermostat on wire JB (pin 1!) , go through the plug to the thermostat wires of different color to the thermostat switches. Also there should be ground on pin 2.
Then when the thermostat switches are set and it calls for heat, you should see 12VDC come back to this plug on the wire from the thermostat that connects to pin 3, Wire JJ!

Sounds difficult but idea is that 12V comes in on pin 1, goes to thermostat and if set right there, the 12V comes back on pin 3 and goes to start the furnace!

Tripped breaker or maybe as simple as the plug is not making good contact in the wall behind the thermostat?

Good luck on the chase and let us know if that makes sense or you find it!

 

[powercat_ras]

If the thermostat display is showing "ER" this indicates that the thermostat is receiving 12 volts and has a good ground.

 

[bigb56]

I'm going to ask this because I really don't know the answer, but if the propane runs out will it lock out all heating? I'm asking because on my Coleman Mach when you select electric heat the furnace always comes on to help get the temp up faster and it will come on again if the temp drops more than 1 or 2 degrees below the setpoint.

 

[RayIN]

I'm going to ask this because I really don't know the answer, but if the propane runs out will it lock out all heating? I'm asking because on my Coleman Mach when you select electric heat the furnace always comes on to help get the temp up faster and it will come on again if the temp drops more than 1 or 2 degrees below the setpoint.

Correct.
That temperature differential is 3° on most thermostats, but my OEM 1999 Colman-Mach thermostat would run the heat pump regardless of temperature differential. I replaced it with a digital model and it will turn on LP heat when the temperature differential is 3° or more.

 

[bigb56]

Correct.
That temperature differential is 3° on most thermostats, but my OEM 1999 Colman-Mach thermostat would run the heat pump regardless of temperature differential. I replaced it with a digital model and it will turn on LP heat when the temperature differential is 3° or more.

So if the furnace runs out of gas will the heat pump still work? I'm thinking it may be possible that it could throw off the sequence causing a shut down/lockout until gas is restored.

 

[RayIN]

So if the furnace runs out of gas will the heat pump still work? I'm thinking it may be possible that it could throw off the sequence causing a shut down/lockout until gas is restored.

ColemanMach heat pump thermostat operation begins on page 8 of The 6535 CM heat pump service manual. Prove chart is on page 9.
.

To keep the heat pump operating without the LP furnace turning on, one must adjust the thermostat up by no more than 3° above inside temperature.
For example; assume indoor temperature is 45°, 'stat must be set on 48°. When 'stat reaches 47° it may be set on 50°, etc.
Any more set difference locks out the heat pump and attempts to turn on the LP furnace.
This is all controlled by the 'stat and heat pump PC board.


FWIW; I've seen my heat pump operating and keeping the MH warm when outside temperature was 39°. That was because indoor temperature was less than 3° below 'stat setting. When the "stat could no longer maintain less than 3° differential it turned on the LP furnace.
Had there been no LP available, I would've had to lower the 'stat setting to keep it operating.

 

[powercat_ras]

I have the model 8530 thermostat on my Vista. When the mode switch is set to Elec Heat it will activate the propane furnace in addition to the heat pump, if the current temperature is 5 degrees or more below the set point.

The 8530 thermostat manual is dated 2008 so this thermostat may not be the same kind that is on OP's 2004 Winnebago.

 

[RayIN]

I have the model 8530 thermostat on my Vista. When the mode switch is set to Elec Heat it will activate the propane furnace in addition to the heat pump, if the current temperature is 5 degrees or more below the set point.

The 8530 thermostat manual is dated 2008 so this thermostat may not be the same kind that is on OP's 2004 Winnebago.

This discussion is for a ColemenMach/RVP basement heat pump only, not roof units.

 

[Morich]

When dealing with an RV that is more than 20 years old, I don't think there is any way to say what they are dealing with until they come back and tell us more.
They mention heat pump, also propane furnace and then they mention reset tries but that leaves a lot of open space to fill!

 

[RayIN]

When dealing with an RV that is more than 20 years old, I don't think there is any way to say what they are dealing with until they come back and tell us more.
They mention heat pump, also propane furnace and then they mention reset tries but that leaves a lot of open space to fill!

The Coleman 8350 will not work with a basement AC/heat pump combo unit, so must be a roof unit.
See: https://www.rvproductsshop.com/8530-3481-black-thermostat-for-coleman-mach-heat-pumps.html Then under "more information".

 

[Kim Petersen]

thanks a lot to all who chimed in with advice. the advice that caught my eye was submitted by Big B :"if you run out of propane the t-stat will lock out"
I had not considered that, and I am out of propane. I will let you know if that kick starts everything again, once I fill the tank.

 

[Jim_HiTek]

Did not care for that automatic propane furnace turn on feature of the TrueAir thermo in my 2002 Winnie so I just clipped the power lead to it and installed a switch I can leave off. Which I do 90% of the time. Might use the propane furnace to take the chill off in the early morning a few times a year but that is about it. And I've never had a problem running the heat pump (basement style) with that switch in the Off position. I don't see any signal from the furnace back to the thermo in the schematics that it's shut down due to no propane but perhaps that's only with the roof mounted heat pumps?

Hmm, just looked at wiring for the 8085 and don't see a out-of-propane wire there either.

 

[RayIN]

Make sure the set temp and actual temp is less than 4°, the heat pump should run. As it heats up inside adjust the 'stat by another 3°.

 

[Kim Petersen]

Update,
filled propane tank today, unhooked t-stat harnesses, after a few minutes plugged everything back in. t-stat display again reads Er. I turned the selector switch to OFF, and the fan came on, blowing through the ceiling vents. if I set temp 3-4 degrees differential from room stat, nothing except air through the ceiling vents.
looks like I'm going to have to "call a friend" LOL

 

[bigb56]

Update,
filled propane tank today, unhooked t-stat harnesses, after a few minutes plugged everything back in. t-stat display again reads Er. I turned the selector switch to OFF, and the fan came on, blowing through the ceiling vents. if I set temp 3-4 degrees differential from room stat, nothing except air through the ceiling vents.
looks like I'm going to have to "call a friend" LOL

Don't give up yet, if your propane ran out there is air in the lines that needs to bleed out. Use the stove or water heater to help bleed the system if they are propane.

 

[ZigZag03]

The Micro-Air stat for this application allows for the auto selection of heat or cool, and you can designate which heat you'd like to run, gas or electric. If you are questioning the thermostat, don't waste too much with the old one. Besides this feature, the wifi and phone app are nice to monitor your coach from the phone. With mine parked and plugged in at the house, I can maintain a comfortable range without ever going aboard. This is what I bought:

https://www.amazon.com/MICRO-AIR-Th...keywords=MICRO-AIR&qid=1738161590&sr=8-5&th=1

 

[jerichorick]

The Micro-Air stat for this application allows for the auto selection of heat or cool, and you can designate which heat you'd like to run, gas or electric. If you are questioning the thermostat, don't waste too much with the old one. Besides this feature, the wifi and phone app are nice to monitor your coach from the phone. With mine parked and plugged in at the house, I can maintain a comfortable range without ever going aboard. This is what I bought:

https://www.amazon.com/MICRO-AIR-Th...keywords=MICRO-AIR&qid=1738161590&sr=8-5&th=1

That was what I was going to suggest.
Here is the Micro-Air direct site: https://www.micro-air.com/products_easytouch_rv_thermostat_touchscreen.cfm
I have one of the early thermostats and took part in beta testing. I had some problems with getting it to work correctly. The support team was fantastic and wanted me to return the t-stat until I told them I had bought it from Amazon. They wouldn't take it back. I found the fuse holder was not making good contact. Once fixed my problems went away. I don't know if they still have this return policy. It might be worth it if they do to buy direct from Micro-Air.
Fantastic thermostat.