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.

[upnorth15]

budwich wrote:
I am sure they know about their product, BUT what happens is that "people usually talk two different languages"... 🙂 they talk "technology / product" while you talk "user / product". Sometimes things don't "translate well".

You can likely follow their direction and get the AC model number from the actual outside unit (this is the big thing on the roof)... maybe a 5XX, or 6XX. However, the controller / relay board is usually inside for ease of access / repair. If you look at your picture of the plate, it indicates that there is wiring leaving the "box" and going up to the AC UNIT. There is also wiring coming from the thermostat and going into the "box".
Knowing what AC unit they installed will help as then when you look at the controller, it should be correlated as a "companion part".

IF you get a chance to talk with a technical person again at dometic, then the question to ask would be "what connections do the colors align with on the label?"... in your picture, you see the color codes of the wire and the connections saying "to thermostat"... each color aligns with some function going into the controller. As you saw in your picture of the thermostat, one can readily see a color to "function" for the wiring. What you need is that "equivalent" description from the label on the control box. IF those don't align, then you will having wiring "mismatch issues" which might be the source of your problem.
IT is strange that two AC units are operating the same way (ie. fan always on). It is unlikely that there is a component failure, more than likely a wiring error or possibly a relay card "mismatch" (unlikely but possible). From the dometic documentation, I am not able to determine the "color to function mapping". If you get this, it may go along way to solving your problem.

In terms of warranty, the AC unit (on the roof) and the controller (inside ceiling housing) are likely replaced together so indeed, it is a warranty issue if either fail. Your problem is the warranty probably doesn't cover "labor" which your "friends" don't appear to want to do for free (in terms of further troubleshooting). That's the "between the rock"... 😞

Thanks again!! I haven't gone looking any further into this because the girl I bought it from said she was going to raise some hell with the dealer. And she did. They are big farmers in the area so ......... Now they've agreed to drop labour charges and if there are parts the girl I bought it from will split costs with me. So hopefully dometic will cover under warranty. Like you said because this is happening with 2 AC's it's likely something deeper going on.
Your info is so great and if you don't mind could I pass it along. I just wonder if these guys know what they are doing!! Still I'm wondering if I even needed a new AC.
One more question? Does a bad compressor in AC typically blow the main breaker in trailer?

[ReferDog]

Call dealer, unit is wired wrong. Only can run fan if the fan wire is getting power, so if switch is off then it must in the wires.

[budwich]

I am sure they know about their product, BUT what happens is that "people usually talk two different languages"... 🙂 they talk "technology / product" while you talk "user / product". Sometimes things don't "translate well".

You can likely follow their direction and get the AC model number from the actual outside unit (this is the big thing on the roof)... maybe a 5XX, or 6XX. However, the controller / relay board is usually inside for ease of access / repair. If you look at your picture of the plate, it indicates that there is wiring leaving the "box" and going up to the AC UNIT. There is also wiring coming from the thermostat and going into the "box".
Knowing what AC unit they installed will help as then when you look at the controller, it should be correlated as a "companion part".

IF you get a chance to talk with a technical person again at dometic, then the question to ask would be "what connections do the colors align with on the label?"... in your picture, you see the color codes of the wire and the connections saying "to thermostat"... each color aligns with some function going into the controller. As you saw in your picture of the thermostat, one can readily see a color to "function" for the wiring. What you need is that "equivalent" description from the label on the control box. IF those don't align, then you will having wiring "mismatch issues" which might be the source of your problem.
IT is strange that two AC units are operating the same way (ie. fan always on). It is unlikely that there is a component failure, more than likely a wiring error or possibly a relay card "mismatch" (unlikely but possible). From the dometic documentation, I am not able to determine the "color to function mapping". If you get this, it may go along way to solving your problem.

In terms of warranty, the AC unit (on the roof) and the controller (inside ceiling housing) are likely replaced together so indeed, it is a warranty issue if either fail. Your problem is the warranty probably doesn't cover "labor" which your "friends" don't appear to want to do for free (in terms of further troubleshooting). That's the "between the rock"... 😞

[upnorth15]

budwich wrote:
OK... thanks for the testing data. It does sound like the control board might have an issue similar to the other link I posted. The control board has a couple of different relays, one could be an issue or as the previous poster indicated, the physical position of the board in the box is such that it is touching something that it shouldn't be (inspect carefully). The two screws on the plate expose the innards of the box which then will get you the number. Remember to turn off the breaker before playing with the box!

Ok thanks. Is this control board typically not part of a new AC install? Possibly the guy at Dometic is mistaken thinking this is under warranty as well. I was told to find the model number by going to AC outside on drivers side and open cover.

[budwich]

further... since you are so good at taking pictures... 🙂
a clearer picture of the wiring at the "jumble" of wires at the box especially where the "twist" connectors are will be useful to show which wires coming form the thermostat are being connected to wires going into the box. And once you get the plate off, a picture of the wiring inside the box would help again.

[budwich]

OK... thanks for the testing data. It does sound like the control board might have an issue similar to the other link I posted. The control board has a couple of different relays, one could be an issue or as the previous poster indicated, the physical position of the board in the box is such that it is touching something that it shouldn't be (inspect carefully). The two screws on the plate expose the innards of the box which then will get you the number. Remember to turn off the breaker before playing with the box!

[upnorth15]

upnorth15 wrote:

budwich wrote:
upnorth15, the wire removal that was suggested won't impact the fan starting up with the AC switched to on or at least it shouldn't.... the system should work normally.... in "actual normal wiring", typically only 4 wires are used and fan control is NOT wired. Those wires are used only for "direct" control of the fan. If you disconnect them at the thermostat as suggested, then the switches for fan control (specifically) will do nothing. If the fan still operates as in your problem, then the issue is likely somewhere else... as suggested by hornnumb2, in the control box area maybe.

Hello again and thank you again. I will try this and keep you posted. Should I just tape off those 2 wires?

AC Fan still runs after unhooking the two fan wires. I called Dometic and they said whatever is wrong is covered under warranty including a control board. Now I just need the model number.

[upnorth15]

budwich wrote:
upnorth15, the wire removal that was suggested won't impact the fan starting up with the AC switched to on or at least it shouldn't.... the system should work normally.... in "actual normal wiring", typically only 4 wires are used and fan control is NOT wired. Those wires are used only for "direct" control of the fan. If you disconnect them at the thermostat as suggested, then the switches for fan control (specifically) will do nothing. If the fan still operates as in your problem, then the issue is likely somewhere else... as suggested by hornnumb2, in the control box area maybe.

Hello again and thank you again. I will try this and keep you posted. Should I just tape off those 2 wires?

[budwich]

upnorth15, the wire removal that was suggested won't impact the fan starting up with the AC switched to on or at least it shouldn't.... the system should work normally.... in "actual normal wiring", typically only 4 wires are used and fan control is NOT wired. Those wires are used only for "direct" control of the fan. If you disconnect them at the thermostat as suggested, then the switches for fan control (specifically) will do nothing. If the fan still operates as in your problem, then the issue is likely somewhere else... as suggested by hornnumb2, in the control box area maybe.

[upnorth15]

Hornnumb2 wrote:
You might check the metal box that holds the control board. (The part that has the wiring diagram on it.) I have had 2 that I have purchased that the standoffs inside the box that hold the board are broke and the pcb shorts against the metal case. You can try to pull out that one bolt holding it and flip it over to see if you hear it moving around in there. Please do with breaker off as there is 120v in there.

Thanks for your reply. We can certainly check that. Can a short be causing the AC fan to run in OFF mode? This is the main problem.

[Hornnumb2]

You might check the metal box that holds the control board. (The part that has the wiring diagram on it.) I have had 2 that I have purchased that the standoffs inside the box that hold the board are broke and the pcb shorts against the metal case. You can try to pull out that one bolt holding it and flip it over to see if you hear it moving around in there. Please do with breaker off as there is 120v in there.

[budwich]

I was looking thru the net at some old similar issues on other setups and one indicated that they replaced the control board (in the ac unit - under the label that you pictured earlier... its not cheap though). There problem was similar that the ac compressor was running and could only stop it by pulling the breaker / fuse.

here is the "example"

http://www.irv2.com/forums/f54/dometic-duo-therm-low-profile-ac-111902.html

[budwich]

it was probably my "typo" that caused the issue ("no" should have been "now"). I am very sorry.

[upnorth15]

budwich wrote:
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.

oops is right... sorry guys I took that all wrong.... but what else is new. Sorry Ozlander I apologize. So walk me thru this. I unwire both the "fan" and "hi fan" wires from thermostat. So when I use the AC how will the fan run then?