AC and furnace both on?

[Octopus Prime]

We have a 2018 Jayflight 26bh.
It's in the 50s tonight, so we turned on the heater. The last time we did this was in March. I recall having trouble with it then, but this time it's different.

1. The furnace and the AC appear to both be operating at the same time. The furnace blows hot when we have it on 79 or 80, but cool (not cold) air blows out of the AC ducts.

2. Also, when we bump the temp down to 78, the furnace starts blowing cool air.
It gets too hot in here on 79 or 80, but too cool with no furnace going at all.

How do I fix these issues?

[ASTMedic]

Originally Posted by Octopus Prime

We have a 2018 Jayflight 26bh.
It's in the 50s tonight, so we turned on the heater. The last time we did this was in March. I recall having trouble with it then, but this time it's different.

1. The furnace and the AC appear to both be operating at the same time. The furnace blows hot when we have it on 79 or 80, but cool (not cold) air blows out of the AC ducts.

2. Also, when we bump the temp down to 78, the furnace starts blowing cool air.
It gets too hot in here on 79 or 80, but too cool with no furnace going at all.

How do I fix these issues?

We had this problem last time we went out. Had the A/C unit blowing air too. We calibrated the thermostat and that stopped it and the furnace ran alone. On my thermostat with it off I hold power and the up button if I remember correctly.

Edit:

"If you install the thermostat and it still acts up, then perform a system initialization by following these steps:
Press and hold the '+' button.
Press and hold the 'On/Off Mode' button.
Hold both buttons down for about three seconds until the screen shows a -- --.
Release both buttons and press the 'On/Off Mode' button again to turn system off.
Press 'On/Off Mode' to turn back on. The thermostat has now been reset."

I saw somewhere that you should do this procedure each time you set up. We had peoblems with our A/C the first time out till we did an initialization and then same issue you described last time out with the furnace.

[ASTMedic]

Here's a how to for the one I have on my 242BHSW

https://youtu.be/R_HJxl5WMyw

[Duke_26]

Coming from a digital Coleman Mach thermostat in my last TT, I struggled with this Dometic thermostat in our new 28BHS at first. It seems very finicky. However, I do like the backlit display and that you can have the AC fan running with the furnace on. Seems like this may help move the heat around a little better. But I haven’t really used it this way too much yet. If I recall correctly, the Coleman Mach was one or the other.

The video above is very helpful.

I do have one question still, is there anyway to have the Dometic thermostat display the ambient temperature? I miss that feature that the Coleman Mach digital thermostat had.

[jimp]

What does the "reset" procedure accomplish???

We have the same Dometic thermostat in our TT (appearance wise anyways) and are having issues with the AC portion short cycling, the fan constantly turns on for about 30-45 seconds, shuts down for 30-45 seconds, and repeats this process.

[o2silverado]

Originally Posted by Duke_26

I do have one question still, is there anyway to have the Dometic thermostat display the ambient temperature? I miss that feature that the Coleman Mach digital thermostat had.

They do not display the room temp. It probably would have cost a extra 50 cents to add that...its always about the bottom line.

[Octopus Prime]

Thank you!
That is very helpful.

[ASTMedic]

Originally Posted by jimp

What does the "reset" procedure accomplish???

We have the same Dometic thermostat in our TT (appearance wise anyways) and are having issues with the AC portion short cycling, the fan constantly turns on for about 30-45 seconds, shuts down for 30-45 seconds, and repeats this process.

Don't really know. I do know we had issues with the AC coming on or staying on and then the AC fan running while the furnace should have been and no furnace. Did the reset and then the furnace ran with no AC fan. Just so long as it works correctly. I use a battery shut off so every time I shut my rig down completely I'll do a reset once I set up.

[jimp]

Thanks for the tip, will try it out.

[Duke_26]

Originally Posted by o2silverado

They do not display the room temp. It probably would have cost a extra 50 cents to add that...its always about the bottom line.

Thank you for confirming that. Seems ridiculous that that feature is not included in a digital thermostat.

I wonder if the Coleman Mach digital thermostat could be wired up to control the Dometic AC and the furnace? Would it still be a wire for wire swap? I really like the simplicity of the Coleman Mach digital thermostat and the fact that it does display the room temperature.

I put the analog Coleman Mach thermostat back in our 26BH when we traded it for the 28BHS, so I still have the digital Coleman Mach available. I planned to put it in the 28BHS when it came in, but they had switched to the Dometic AC, so I’m not sure if it would work or not. If it will fairly easily, I will swap it out in a heartbeat.

[o2silverado]

Originally Posted by Duke_26

I wonder if the Coleman Mach digital thermostat could be wired up to control the Dometic AC and the furnace? Would it still be a wire for wire swap? I really like the simplicity of the Coleman Mach digital thermostat and the fact that it does display the room .

I don't believe so. The dometic uses a 3 wire system . I think the Coleman still uses the standard thermostat wiring configuration. I believe this is why there is the issue's like this with the Dometic.

[Duke_26]

Originally Posted by o2silverado

I don't believe so. The dometic uses a 3 wire system . I think the Coleman still uses the standard thermostat wiring configuration. I believe this is why there is the issue's like this with the Dometic.

Thank you again!

[2edgesword]

We had the same thing happening. Change the fan setting from "auto" to high or low.

[Forelyndogs]

I guess I'm a bit mystified by this thread. This appears to be an issue with new Dometic thermostats. We have a 2014 Greyhawk with a Coleman thermostat. We can choose Cooling, Off, Gas Heat or Electric Heat. We also have the choice to have the a/c fan cycle or run continuously, but only when either the Electric heat of the Cooling is on. Now the part of this discussion that has me confused is the notion of the A/C running with the gas heat. In our unit if we choose "Electric Heat" the roof unit (the A/C) turns into a heat pump and pulls warmth out of the outside air. (Essentially, it reverses the cooling which pulls warm air out of the inside of the coach and exhausts that air outside.) This works great when the outside temp is above about 45. Sucks when it isn't. What does this have to do with running both at the same time? If the thermostat is set more than five degrees above the interior temp the roof unit will come on AND the gas furnace will also run. Also, if the roof unit isn't working well (outside temp too low), then eventually the set temp will wind up being more than five degrees higher than the actual temp and the roof unit will continue to run (blowing nice cold air) and the gas furnace will come. At first, I thought this was what the original question was about, then I read more and discovered it was all about the thermostat. Guess I"m glad I have a boring old Coleman thermostat.

[2OLDMONKEYS]

Originally Posted by Octopus Prime

We have a 2018 Jayflight 26bh.
It's in the 50s tonight, so we turned on the heater. The last time we did this was in March. I recall having trouble with it then, but this time it's different.

1. The furnace and the AC appear to both be operating at the same time. The furnace blows hot when we have it on 79 or 80, but cool (not cold) air blows out of the AC ducts.

2. Also, when we bump the temp down to 78, the furnace starts blowing cool air.
It gets too hot in here on 79 or 80, but too cool with no furnace going at all.

How do I fix these issues?

Just returned from a very cold trip to Oregon and suffered the same problem. Some vents had air coming out and then at other times they didn’t. Blowing cold air at times then hot again. I kept turning up the temp. One night turned it all off in frustration and in the a.m. it was 44 degrees! We thought something was wrong with the thermostat. Not sure how to solve this.

[2edgesword]

Originally Posted by Forelyndogs

I guess I'm a bit mystified by this thread. This appears to be an issue with new Dometic thermostats. We have a 2014 Greyhawk with a Coleman thermostat. We can choose Cooling, Off, Gas Heat or Electric Heat. We also have the choice to have the a/c fan cycle or run continuously, but only when either the Electric heat of the Cooling is on. Now the part of this discussion that has me confused is the notion of the A/C running with the gas heat. In our unit if we choose "Electric Heat" the roof unit (the A/C) turns into a heat pump and pulls warmth out of the outside air. (Essentially, it reverses the cooling which pulls warm air out of the inside of the coach and exhausts that air outside.) This works great when the outside temp is above about 45. Sucks when it isn't. What does this have to do with running both at the same time? If the thermostat is set more than five degrees above the interior temp the roof unit will come on AND the gas furnace will also run. Also, if the roof unit isn't working well (outside temp too low), then eventually the set temp will wind up being more than five degrees higher than the actual temp and the roof unit will continue to run (blowing nice cold air) and the gas furnace will come. At first, I thought this was what the original question was about, then I read more and discovered it was all about the thermostat. Guess I"m glad I have a boring old Coleman thermostat.

I think some of the confusion comes from the fact that some people have the A/C-heat pump combination while others have an A/C and separate propane furnace for heat. I have an A/C unit and separate propane furnace. If the thermostat fan setting is set on "auto" both the furnace fan and A/C fan will blow when the temperature is below the thermostat setting. To avoid this I have to switch the fan setting from "auto" to either "high" or "low". With the fan setting on "high" or "low" only the furnace fan operates providing heat when the temperature is below the thermostat setting.

[Racinforthefinish]

X2

[2OLDMONKEYS]

We have 2016 Grayhawk with Coleman heat/ac. We have tried settings on both Auto and On positions Hi/Lo (which is a different switch than Auto/On) and get the same results: cold coming from above (a/c) and at times no heat or air coming from low vents (heat). We are stumped as to how to rectify the problem of both running at the same time or heat not running at all. All too confusing for my brain. When I’m hot I want a/c. When I’m cold I want heat. How hard should it be??

[2OLDMONKEYS]

The AUTO switch is separate from the HI LOW switch on our Coleman (2016 grayhawk). the Auto switch is either on Auto or ON.

[pconroy]

Originally Posted by 2OLDMONKEYS

We have 2016 Grayhawk with Coleman heat/ac. We have tried settings on both Auto and On positions Hi/Lo (which is a different switch than Auto/On) and get the same results: cold coming from above (a/c) and at times no heat or air coming from low vents (heat). We are stumped as to how to rectify the problem of both running at the same time or heat not running at all. All too confusing for my brain. When I’m hot I want a/c. When I’m cold I want heat. How hard should it be??

We have a 2016 Greyhawk. Also Coleman Mach 3 Heat/AC unit.
Does your thermostat look like ours?


Auto/On - just controls the fan (more or less). I leave it on Auto.

Cold - AC.
Gas Heat - fires up the furnace.
Elec Heat - fires up the Heat Strips in the AC unit -- and possibly the furnace.



What are you experiencing?