Trouble-shooting the A/C

[THenne1713]

The AC controls are 12vdc, POWER TO THERMOSTAT FROM CIRCUIT BOARD located in RETURN AIR DUCT

[f14av8r]

While you are in there, replace that thermostat with the bluetooth version. Then you can manage your AC from your easy chair on your smart phone!

[papademuchos]

Ok, dumb question: where is the return air duct? That's not the vent where the cold air comes out, is it? I pulled off one side, but need more time / more tools to open up the other side... or is it something else?

[youracman]

1. Remove the fasteners as if you were going to change/clean the air filter. (You should do this often in an RV......they get dirty pretty quickly.) 2. Remove the filter and you will be looking at the return air duct.

My rig is enroute home from a trip to Canada (daughter and grandkidz have it) or I would take a pic or two for you ...... hopefully of the ckt bd/wiring THenne refers to. I'll do that this coming week and if it works out OK I will post (just for the archives) ...... and maybe it will help someone else one day.

Best........... Ed S

[papademuchos]

Thanks again for the ideas and suggestions on where to look. I believe my problem is here in the wiring connections to the thermostat. I opened this up before, but never pulled the wires out this far from the wall:



Before looking at the wiring, I opened up the air duct (thanks youracman) and looked inside. I'm assuming that's the circuit board up inside there:



I also pulled out the white plug in the lower part of this picture, thinking that's the source of power to the circuit board:



After doing that, I pulled the wires out of the wall that connect to the thermostat. I tested some things - didn't really find anything. Then as soon as I plugged the white cord back in, the fan came on! (The thermostat had been left in the Cool / On (Low air) position). When I pulled the wires out I must've reconnected some of them that were loose.

I started to push the wires back into the wall and then it turned off. At first I thought it was the red wire connection, but now I'm thinking it's the yellow or the white. I'm away from home this week, but as soon as I get back on Sunday I plan to re-wire all of these... just to make sure all connection are tight and secure.

I'm super happy it's just a loose wire issue! Dollar signs were popping up in my head... or the hassle of trying to order an 18 year old circuit board replacement. I'll try to follow up with another post on Sunday just to close this out, but I'm pretty sure this is my issue.

Thanks again to everyone for your suggestions! Little by little I'm learning more about this rig.

[SantaFeSky]

I’ve had my troubles with the Coleman mach 15k. On the third thermostat and second control board. It’s under warranty but good luck getting a dealer to fix your a/c when you need it. And if you want to pay extra buy your parts at Camping World, they charged me $257 for a thermostat Coleman lists retail around $160 (still an abomination).

First step to diagnose is pull your thermostat, it lifts up and out, then check your leads with a meter as you walk through each,setting, fan lo fan high cool low cool high cool low auto coll high auto and heat. Each time you should see 12v on the corresponding wire. Their web site has all the lead definitions, just Google to find it.

If that checks out then the problem is in the unit. The issue can be the control board, a capacitor or a motor (or a wire of course.). Start by repeating the thermostat test but at the control board end of the wiring. It’s harder or at least more dangerous to check the control board outputs because they are 120v and are enclosed in a wiring harness plug. One issue with the control boards is a relay being stuck either open or closed. My control board failure (straight from the factory) was a compressor that never shut off - relay stuck closed.

The control boards are easy to replace, remove the inside cover and faceplate, 2 spring nuts and out it drops.

That worked great for a week and then the thermostat went. CW replaced that in a mere 3+ months wait. It lasted 3 days. Failed in Texas in 102 degree heat. DW said if I could fix it ok but if not we were getting a hotel room and abandoning the POS in the campground. The math here was 10 days times $150 night versus ….

In the end yes it was easy to fix as long as you can do the diagnostics. If it’s on the roof my preference is a professional but anything other than the capacitors is above my pay grade,

At some point just junking the rooftop unit and dropping in a new one is easier. I spent $400 on parts, a new unit would have been $850 (or $1700 at CW).

One thing to remember is these units are sealed so if it is in the compressor, or Freon system it’s toast.

[THenne1713]

So what is room temp and thermostat setting?

[THenne1713]

The thermostat and control circuit board/ RELAYS for air conditioner use 12vdc/ battery power to turn the 120vac to the air conditioner ON/OFF. No 12vdc= No air on most w/ remote thermostat.

[papademuchos]

I finally found the culprit to my problem! At first I thought it was the wires connected directly to the thermostat - some of them seemed loose. However, after replacing the butt connectors on all them, I was still experiencing a problem with a "loose wire". When I would start to push the wires back up into the wall, it would cut out and turn off. When I would pull them back a little, then it would turn on.

In my unit, the thermostat is just under a cabinet in kitchen. On the left side of the cabinet are the meters and the generator switch. I pulled that cover off and discovered a whole "mess" of wires behind it. All of the wires going to the thermostat were in this area as well. After a bit of pulling and pushing I discovered the problem was with the red wire coming out on the right side of this blue splice connector:



The two wires coming in and out of this connection are different sizes and perhaps that was contributing to the problem. After replacing the connector with something different my A/C works every time now.

Thanks again to everyone for your suggestions and ideas! I appreciate all the help and ultimately they led me down the right trail.

[Solo_RV_Guy]

Originally Posted by papademuchos

I finally found the culprit to my problem! At first I thought it was the wires connected directly to the thermostat - some of them seemed loose. However, after replacing the butt connectors on all them, I was still experiencing a problem with a "loose wire". When I would start to push the wires back up into the wall, it would cut out and turn off. When I would pull them back a little, then it would turn on.

In my unit, the thermostat is just under a cabinet in kitchen. On the left side of the cabinet are the meters and the generator switch. I pulled that cover off and discovered a whole "mess" of wires behind it. All of the wires going to the thermostat were in this area as well. After a bit of pulling and pushing I discovered the problem was with the red wire coming out on the right side of this blue splice connector:

Attachment 370054

The two wires coming in and out of this connection are different sizes and perhaps that was contributing to the problem. After replacing the connector with something different my A/C works every time now.

Thanks again to everyone for your suggestions and ideas! I appreciate all the help and ultimately they led me down the right trail.

Thanks for the update! This is useful info and will help others with yet another place to look for failure points.

[youracman]

Originally Posted by Solo_RV_Guy

Thanks for the update! This is useful info and will help others with yet another place to look for failure points.

X2

We all like a "DIYer happy ending" story.....and pictures to boot! Good work. No service call, no parts, no waiting on people for days or weeks. Keep reading this forum ............. you will learn a lot; at least I do.

Good times and safe travels to ya.

[THenne1713]

FYI, it was a similar "scotchlock-style" connector that I finally found after 3-years was the culprit in my REAR CAMERA VIDEO STATIC (including 3-differnt camera systems) ONLY WHEN ENGINE RUNNING; a #22 wire to a power plug to the AV wireless receiver was the CULPRIT that (made me thinK) that the issue was IGN generated, as the static only evident when engine running. Replacing with a larger wire power plug and a DOLPHON crimp connector w/ Sealant cured MY issue. Great Job, Good Luck.

[Diesel-Lover]

[QUOTE=papademuchos;6234617]I finally found the culprit to my problem!




Hey way to Gunshoe it to the fruitful end. You are a regular Paul Drake and Perry Mason rolled up in one! Hopefully Della pitched in too!


Good dig and find. BTW if your Rheem stat (honeywell programmable thermostat) starts to act wonky the control board on the air handler has a 3 amp auto blade fuse on it, its light pink and probably busted. Just happened to me over the loooooong hot weekend! Looked high and low there was no voltage on a line checked all the breakers and such thought it was the outside unit etc, ends up the air handler.... and then to reset the outside compressor as well. All is well and crisp and cool. Now if there was a magical cure to keep the electric meter from going bonkers!

[THenne1713]

(FOR INFO/ DISCUSSION) The CIRCUIT BOARD (bit higher priced than I wudda guessed :-( ) = RELAYS to control the 120vac COMPRESSOR HIGH/ FAN HIGH/ FAN LOW (note the three relays on the board?) using 12vdc thermostat, but also INPUT for FREEZE-STAT to shut down compressor when coil icing reaches a certain point.


https://www.rvupgradestore.com/Colem...xoCDgMQAvD_BwE