HELP----AC fan blows when thermostat is set to OFF

[upnorth15]

I just had a new AC installed in my 2009 travel trailer. Crazy thing is happening.. The only way to turn the AC fan off is to flip the AC breaker or unplug the trailer from power. This is a non-digital thermostat and there are no controls on the AC itself. The furnace works great and is controlling heat via thermostat. Any ideas what this could be before I take it back to the shop?? They are not to helpful and are planning to charge us again... saying it's not a problem with the install of the new AC. Thanks in advance.

[budwich]

ooops... ??? not sure why the "No thanks Ozlander. " His suggestion is good. It will likely stop the AC fan from running all the time and will likely just have the fan running ONLY when the AC is on.

[upnorth15]

Ozlander wrote:
The first thing I would do is disconnect the orange and blue wires from the fan terminals on the thermostat.
Then we can go from there.

Sorry I was way off base there. Sorry about that.. :? So is this disconnect of wires fan and hi fan helping with troubleshooting the problem? I'm game if you can help me with the walk thru from there.

[budwich]

now "we" are talking... should have asked for that picture sooner.

[Ozlander]

The first thing I would do is disconnect the orange and blue wires from the fan terminals on the thermostat.
Then we can go from there.

[upnorth15]

budwich wrote:
no problem. If you can post a picture of the wiring at your thermostat (pull off the cover) so that you / we can see the terminal and wire connections. We might get an idea of what your next steps might be... ie. chasing wiring or otherwise. According to some dometic wiring, there should be 6 wires at the thermostat. Less may mean that some "mods" were done previously instead of running additional cabling.... and those "mods" may not have been as "expected".

here's a pic

[budwich]

no problem. If you can post a picture of the wiring at your thermostat (pull off the cover) so that you / we can see the terminal and wire connections. We might get an idea of what your next steps might be... ie. chasing wiring or otherwise. According to some dometic wiring, there should be 6 wires at the thermostat. Less may mean that some "mods" were done previously instead of running additional cabling.... and those "mods" may not have been as "expected".

*** removed a portion as I misread the wiring diagram ****

[upnorth15]

budwich wrote:
😞

I think they had a "couple of issues" ("onion skin" so to speak). The AC problem had some issue since it was blowing fuses (likely a motor issue / compressor problem) but the "fan on" issue was also there all along which might still be a wiring error (either at the thermostat or AC box), since it is likely that the "installer" might have only did a "unplug/plug" and things "worked" thereafter (ie. no fuse blowing). Anyways, I don't see an easy way out without doing some good wiring investigation which will take time and understanding which will mean $$ if you don't do most of it yourself. 😞

Too bad the country is so big ... 🙂

That's for sure!! Might be cheaper to fly you out here to fix it. The wishy washy poor customer service seems to be the norm anymore. You've been great and educated me so I've got some knowledge of what might be going on when I talk to them again. Thanks again Kathy

[budwich]

😞

I think they had a "couple of issues" ("onion skin" so to speak). The AC problem had some issue since it was blowing fuses (likely a motor issue / compressor problem) but the "fan on" issue was also there all along which might still be a wiring error (either at the thermostat or AC box), since it is likely that the "installer" might have only did a "unplug/plug" and things "worked" thereafter (ie. no fuse blowing). Anyways, I don't see an easy way out without doing some good wiring investigation which will take time and understanding which will mean $$ if you don't do most of it yourself. 😞

Too bad the country is so big ... 🙂

[upnorth15]

budwich wrote:
OK... so now you are getting to the "root cause" of the problem... although you didn't indicate why the ac was changed out.

Basically, there are "considerations" when trying to wire an AC unit in a travel trailer. The heating / furnace work on 12v systems entirely while the AC needs 120v... so there are different relay "options" that need to be used. Dometic offers a "few" different ones. Overall, the system is relatively simple in terms of electronics and tracing IF you have a little electrical knowledge and a meter. My guess based on my limited experience converting / adding a digital thermostat to my system (which is coleman based I think). The fan selection / speeding will not having any effect on the furnace operation as the furnace control takes care of it all. Basically, the thermostat just causes an "ON/OFF" function based on the temperature.

The AC side has more "considerations". My old dometic analog only had heating (two wires only) so I don't have much more to go on other than what I have read on the various sites.

Again, you need to look at the wires that are at the thermostat (copy down the terminal and color) then "trace" this over to the "jumble" and see which colors show up there, and then even further, you need to see which wires go where inside the AC "box" where the relays and others terminals are. From there, it will likely be possible to understand the issue... hopefully.

I guess depending on what the "work order" was with the install company, their stance of "it will cost you" is probably "reasonably" IF it was stated as "replace my AC UNIT" which they did. It appears that the "real problem" was never addressed or "paid for" to get resolved.

Thank you so much for all your info. It is very helpful. They were told to fix the AC. We never told them to replace it. The girl that works at this RV place was the seller's best friend.(girl we bought it from) She just told us they would look at the AC and fix it and said it might have to be replaced. They told us it was the compressor!! and also told us they tested the system.

[budwich]

OK... so now you are getting to the "root cause" of the problem... although you didn't indicate why the ac was changed out.

Basically, there are "considerations" when trying to wire an AC unit in a travel trailer. The heating / furnace work on 12v systems entirely while the AC needs 120v... so there are different relay "options" that need to be used. Dometic offers a "few" different ones. Overall, the system is relatively simple in terms of electronics and tracing IF you have a little electrical knowledge and a meter. My guess based on my limited experience converting / adding a digital thermostat to my system (which is coleman based I think). The fan selection / speeding will not having any effect on the furnace operation as the furnace control takes care of it all. Basically, the thermostat just causes an "ON/OFF" function based on the temperature.

The AC side has more "considerations". My old dometic analog only had heating (two wires only) so I don't have much more to go on other than what I have read on the various sites.

Again, you need to look at the wires that are at the thermostat (copy down the terminal and color) then "trace" this over to the "jumble" and see which colors show up there, and then even further, you need to see which wires go where inside the AC "box" where the relays and others terminals are. From there, it will likely be possible to understand the issue... hopefully.

I guess depending on what the "work order" was with the install company, their stance of "it will cost you" is probably "reasonably" IF it was stated as "replace my AC UNIT" which they did. It appears that the "real problem" was never addressed or "paid for" to get resolved.

[upnorth15]

budwich wrote:
OK... thanks for the extra info.
hmmm, why the changed out of the AC? Asking cause maybe if there was an issue, the thermostat might be at issue and was never "root caused" by anyone.

You are likely going to have to have someone look at it if you aren't willing to do some "disassembly" of some areas to get better looks at things. There are relay boards under the panel in your picture that are based on "system needs" along with how they have been connected to the wires showing.

Further, the wiring at the thermostat needs to be identified specifically to see what wiring is leaving there and going to the "jumble" of wires in your picture that ultimately need to go to the relay board that I mentioned.
Ultimately, lots of tracing / tracking to determine where the problem lies.
Since the original company isn't very "co-operative", you are likely stuck between "rocks". 😞

I just got off the phone with the previous owner of the trailer. OMG she tells me that the AC fan was always running in OFF mode for her too and blowing the breaker. Same problem as I have with a brand new AC installed. There never sourced the problem. Could a digital thermostat fix it? Is the control panel part of the AC?

[budwich]

OK... thanks for the extra info.
hmmm, why the changed out of the AC? Asking cause maybe if there was an issue, the thermostat might be at issue and was never "root caused" by anyone.

You are likely going to have to have someone look at it if you aren't willing to do some "disassembly" of some areas to get better looks at things. There are relay boards under the panel in your picture that are based on "system needs" along with how they have been connected to the wires showing.

Further, the wiring at the thermostat needs to be identified specifically to see what wiring is leaving there and going to the "jumble" of wires in your picture that ultimately need to go to the relay board that I mentioned.
Ultimately, lots of tracing / tracking to determine where the problem lies.
Since the original company isn't very "co-operative", you are likely stuck between "rocks". 😞

[upnorth15]

budwich wrote:
Yes, the cowling that I refer to is the "trim ring" holding the filter BUT on a number of other dometics, it houses the control panel. I am still suspicious of the "combination" of manual thermostat with a "new AC" as dometic went to a digital controller / thermostat a while ago.
I think you really need to find out what model of AC was installed as that will likely help with understanding what controller it is equipment with.

Actually, back up a bit.

What equipment did they actually install??? What thermostat was originally there?

They installed a new AC unit only. I looked at the trailer once before I bought it and the unit on top was white and looked smaller. Now it's black and looks bigger. The thermostat is the original. I don't know where to find the model # other than call Dometic and see if they can find it via the serial #

[budwich]

Yes, the cowling that I refer to is the "trim ring" holding the filter BUT on a number of other dometics, it houses the control panel. I am still suspicious of the "combination" of manual thermostat with a "new AC" as dometic went to a digital controller / thermostat a while ago.
I think you really need to find out what model of AC was installed as that will likely help with understanding what controller it is equipment with.

Actually, back up a bit.

What equipment did they actually install??? What thermostat was originally there?

[upnorth15]

budwich wrote:
One more question, what happens with the furnace side of the operation?
Do you have a picture of the lower cowling of the AC (ceiling trim ring). Its unusual to not have some form of manual controls for the AC unit especially with the manual thermostat (which has been discontinued by dometic).

Thanks again.. The furnace works fine and it is regulating according to the the temp setting but the AC fan runs steady in furnace mode too. I have to flip AC breaker when using the furnace. Can you explain what the lower cowling and ceiling trim ring are? Are you meaning the plastic cover that holds the filter? Thanks Kathy