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Old 04-05-2019, 01:16 AM   #1
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THOR #11774
A/C Fan Won't Turn Off

I swapped out my thermostat yesterday and all was well.

Today I turned on the A/C fan for a bit and now it won't turn off.

Here is what I have tried:
- turned off/on the shore power. Fan came back on with the power.
- removed the thermostat. (Fan stayed running)
- wired up the original thermostat. A/C and heat all run fine but the fan still stays running.

Note that I am referring to the A/C fan not the heater fan.

I'm thinking it may be a stuck fan relay but I've never gone into the A/C unit from above.

Heading out on a trip next week and would rather not call a mobile tech if it's something I can do myself.

Any suggestions?
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Old 04-05-2019, 02:34 AM   #2
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If you are saying that when you flip the fan switch from on to auto that the fan still stays on when the AC is off then I’d say that somehow you wired the “auto” AC fan switch to a “hot” wire. The auto fan setting is basically an off switch for the fan when the AC compressor is not operating. If u tried two different thermostats and it still stays on, then both the on and the auto fan settings are getting power all the time. The auto side should only get power when the compressor is running.
The wire connections from the thermostat to the AC unit are located up in the ducting inside the coach. It is accessed by removing the inside panels of the AC unit. You do not have to remove the outside roof cover. You cannot access them from there. There is a box up in the ducting where the wires from the thermostat connect to the AC unit. However, since this problem occurred after fooling with your thermostat, the thermostat wiring is probably the issue.
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Old 04-05-2019, 02:48 AM   #3
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Originally Posted by Oneilkeys View Post
If you are saying that when you flip the fan switch from on to auto that the fan still stays on when the AC is off then I’d say that somehow you wired the “auto” AC fan switch to a “hot” wire. The auto fan setting is basically an off switch for the fan when the AC compressor is not operating. If u tried two different thermostats and it still stays on, then both the on and the auto fan settings are getting power all the time. The auto side should only get power when the compressor is running.
The wire connections from the thermostat to the AC unit are located up in the ducting inside the coach. It is accessed by removing the inside panels of the AC unit. You do not have to remove the outside roof cover. You cannot access them from there. There is a box up in the ducting where the wires from the thermostat connect to the AC unit. However, since this problem occurred after fooling with your thermostat, the thermostat wiring is probably the issue.


Since I had replaced the thermostat the day before, it was the first thing I suspected.

I would have expected that by fully removing the thermostat that the fan would have turned off, but it still runs.
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Old 04-05-2019, 01:39 PM   #4
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I would too, but the system is pretty simple, so if the compressor is off and the fan switch is on auto, then the fan is still getting power somehow. Did this happen immediately when you replaced the thermostat or did the system work correctly initially and then not turn off on auto? One other question? Did your new thermostat have a high and low fan switch and how did you wire it if it did not?

If the wiring at the thermostat is not the problem, then it is may be the box up in the vent. You might check to see if the auto side of the fan switch at the thermostat has constant power as does the “on” side with the thermostat connected.

If I understand your first post correctly, your fan runs with no thermostat connected at all. Since I believe the fan is powered by the fan wire being connected to the red power wire at the thermostat, if the fan runs with all the wires at the thermostat disconnected then that fan wire must be receiving 12v from somewhere. I would check to see if it is “hot” with a volt meter and if it is, find the box under the AC and disconnect that wire from the box. It is a spade connector and just pulls out. If the fan stops, you’ve isolated it to that wire. If the fan continues to run with that wire disconnected at the box, then that box might be bad.
Good luck. 12v electrical issues are so much “fun”. I finally called in an AC guy on my issues after I installed a new thermostat. Turned out that the info I got on the internet was incorrect and you could not combine the high and low fan wires. When you did, it confused the “box” which didn’t know whether it should be on high or low speed and kept shutting down the compressor. I could have played with it forever and never solved the problem. Glad I spent $100 and had a professional fix it by disconnecting one wire. Better that than having a “hot” wife complain thru the entire trip.
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Old 04-05-2019, 02:58 PM   #5
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Originally Posted by Oneilkeys View Post
I would too, but the system is pretty simple, so if the compressor is off and the fan switch is on auto, then the fan is still getting power somehow. Did this happen immediately when you replaced the thermostat or did the system work correctly initially and then not turn off on auto? One other question? Did your new thermostat have a high and low fan switch and how did you wire it if it did not?

If the wiring at the thermostat is not the problem, then it is may be the box up in the vent. You might check to see if the auto side of the fan switch at the thermostat has constant power as does the “on” side with the thermostat connected.

If I understand your first post correctly, your fan runs with no thermostat connected at all. Since I believe the fan is powered by the fan wire being connected to the red power wire at the thermostat, if the fan runs with all the wires at the thermostat disconnected then that fan wire must be receiving 12v from somewhere. I would check to see if it is “hot” with a volt meter and if it is, find the box under the AC and disconnect that wire from the box. It is a spade connector and just pulls out. If the fan stops, you’ve isolated it to that wire. If the fan continues to run with that wire disconnected at the box, then that box might be bad.
Good luck. 12v electrical issues are so much “fun”. I finally called in an AC guy on my issues after I installed a new thermostat. Turned out that the info I got on the internet was incorrect and you could not combine the high and low fan wires. When you did, it confused the “box” which didn’t know whether it should be on high or low speed and kept shutting down the compressor. I could have played with it forever and never solved the problem. Glad I spent $100 and had a professional fix it by disconnecting one wire. Better that than having a “hot” wife complain thru the entire trip.
He completely removed the thermostat and the fan still ran so unless he cross-connected the wiring itself, which I doubt since the fan didn't run after replacing the thermostat until he turned it on, and now it runs forever.

So my vote is for a stuck fan relay. OP go upstairs, remove the AC cover and find the relay.
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Old 04-05-2019, 03:23 PM   #6
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THOR #11774
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Originally Posted by 16ACE27 View Post
He completely removed the thermostat and the fan still ran so unless he cross-connected the wiring itself, which I doubt since the fan didn't run after replacing the thermostat until he turned it on, and now it runs forever.



So my vote is for a stuck fan relay. OP go upstairs, remove the AC cover and find the relay.


I think I have traced the problem down to the relay on the circuit board (which is accessible from in the coach)

Called Thor who said it was a Coleman warranty issue. I called Coleman who said the controller was handled by anothet group (RV Products).

I ended up with their tech support who confirmed my diagnosis and will replace the control board under the two year Coleman warranty.

Only issue is I need the serial number which is under the cover up top and it's raining today.

Once I get the serial number and replacement board it will take about 15 minutes to replace.

Worst case is I buy a new board on eBay ($75). Still better than a trip to CW.
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Old 04-05-2019, 03:28 PM   #7
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Your coach may have a build sheet attached inside a bedroom closet that lists all the major components complete with serial numbers.....might save you a trip North .......if you can find it.
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Old 04-05-2019, 03:30 PM   #8
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Good for u. I bet Thor could give you the serial# of ur AC is you asked for a build sheet for your unit.
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Old 04-05-2019, 03:45 PM   #9
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THOR #11774
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Originally Posted by javelin View Post
Your coach may have a build sheet attached inside a bedroom closet that lists all the major components complete with serial numbers.....might save you a trip North .......if you can find it.


Great idea. I was aware of the component list but never thought about it in this case.

Unfortunately, everything except the AC'S are on the list.

Want to check out the sealant anyway so a climb to the roof is not that big of a deal.
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Old 04-05-2019, 03:59 PM   #10
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THOR #11774
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Originally Posted by Oneilkeys View Post
I would too, but the system is pretty simple, so if the compressor is off and the fan switch is on auto, then the fan is still getting power somehow. Did this happen immediately when you replaced the thermostat or did the system work correctly initially and then not turn off on auto? One other question? Did your new thermostat have a high and low fan switch and how did you wire it if it did not?



If the wiring at the thermostat is not the problem, then it is may be the box up in the vent. You might check to see if the auto side of the fan switch at the thermostat has constant power as does the “on” side with the thermostat connected.



If I understand your first post correctly, your fan runs with no thermostat connected at all. Since I believe the fan is powered by the fan wire being connected to the red power wire at the thermostat, if the fan runs with all the wires at the thermostat disconnected then that fan wire must be receiving 12v from somewhere. I would check to see if it is “hot” with a volt meter and if it is, find the box under the AC and disconnect that wire from the box. It is a spade connector and just pulls out. If the fan stops, you’ve isolated it to that wire. If the fan continues to run with that wire disconnected at the box, then that box might be bad.

Good luck. 12v electrical issues are so much “fun”. I finally called in an AC guy on my issues after I installed a new thermostat. Turned out that the info I got on the internet was incorrect and you could not combine the high and low fan wires. When you did, it confused the “box” which didn’t know whether it should be on high or low speed and kept shutting down the compressor. I could have played with it forever and never solved the problem. Glad I spent $100 and had a professional fix it by disconnecting one wire. Better that than having a “hot” wife complain thru the entire trip.


I am installing a residential WIFI thermostate. I was aware that I would only be able to use one of the fan speed wires (unless I install an external switch). Since the difference between high and low is not that much, I'm using the high.

The thermostat I got requires a 'C' wire so I had purchased a separate 24v AC adapter. I'm going to return it and get one with batteries that does not require a 'C' wire. I found it to be a pain to run the adapter wire to a plug connected to my inverter.
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Old 04-05-2019, 04:01 PM   #11
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THOR #11774
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Originally Posted by 16ACE27 View Post
He completely removed the thermostat and the fan still ran so unless he cross-connected the wiring itself, which I doubt since the fan didn't run after replacing the thermostat until he turned it on, and now it runs forever.



So my vote is for a stuck fan relay. OP go upstairs, remove the AC cover and find the relay.


Actually, I can access everything including the circuit board / relay from below.

I just need the A/C serial number for warranty coverage and that is under the cover up top.

Probably only take 15 minutes to swap out the new board once I get it.
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Old 04-05-2019, 04:06 PM   #12
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THOR #3156
Quote:
Originally Posted by dave.irwin.59@gmail.com View Post
I am installing a residential WIFI thermostate. I was aware that I would only be able to use one of the fan speed wires (unless I install an external switch). Since the difference between high and low is not that much, I'm using the high.

The thermostat I got requires a 'C' wire so I had purchased a separate 24v AC adapter. I'm going to return it and get one with batteries that does not require a 'C' wire. I found it to be a pain to run the adapter wire to a plug connected to my inverter.
do they make wifi thermostats that will run on batteries. All the ones ive seen require c wire

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Old 04-05-2019, 04:14 PM   #13
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THOR #11774
A/C Fan Won't Turn Off

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Originally Posted by halfprice View Post
do they make wifi thermostats that will run on batteries. All the ones ive seen require c wire

Jerry


Honeywell does. I have three of them already and they say they don't need a C wire.

For the coach I picked up a slightly cheaper Honeywell model (on sale) that requires the C wire so I bought a C wire adapter for $12. But once I figured out the parts to put in a power plug under the bench seat (can't have the adapter wires showing) and the hassle, I should have gotten the better thermostat in the first place.

Planning to swap it out.

Here is the app all setup. The coach is off-line while I deal with the relay issue.

Click image for larger version

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ID:	16509
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Old 04-05-2019, 06:17 PM   #14
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Originally Posted by dave.irwin.59@gmail.com View Post
Honeywell does. I have three of them already and they say they don't need a C wire.

For the coach I picked up a slightly cheaper Honeywell model (on sale) that requires the C wire so I bought a C wire adapter for $12. But once I figured out the parts to put in a power plug under the bench seat (can't have the adapter wires showing) and the hassle, I should have gotten the better thermostat in the first place.

Planning to swap it out.

Here is the app all setup. The coach is off-line while I deal with the relay issue.

Attachment 16509
I have the Honeywell in the house. THe ones I saw at Home Depot all require the C wire THey must have been the cheaper models. Would be nice to have one in the mh.
If you get one please post the model number


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Old 05-28-2019, 03:05 PM   #15
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THOR #11774
I looking to replace my stock thermostates and was thinking of a WiFi unit for at least one of them.

I was in a discount store a few weeks ago and came across Honeywell programmable thermostates for $3 each. I simply could not pass this up. They don't require a 'C' wire which is perfect for the coach.

Very simple install and only had to change a couple of the default settings.

Since we are away from our rig for weeks at a time I want to manage humidity and am planning to leave both thermostats set to 99 degrees (basically off) and then have the front one cool to 78 for an hour mid-morning and the back one cool to 78 in the late afternoon.

I monitor the actual humidity by pointing a Webcam at a digital thermometer.

Will still probably look to upgrade on to WiFi in the future.
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