AC and Heat Suddenly Stopped Working

newbold1 · 03-29-2015, 08:53 PM

I could use some help. My wife and I went camping this weekend and we didn't need to run our AC at all but did run the propane heat just a bit. When it warmed up we ran the AC fan without the compressor when it got stuffy inside. Everything seemed to be just fine.

I got home today from the trip and now suddenly the AC and heat are both completely unresponsive. I have a digital Honeywell thermostat with a toggle switch for Hi/Low fan speed. It's been working for many months without any problem. Nonetheless I pulled the thermostat to check things out and found that I had no 12 volt power coming to the thermostat.

Finding no 12 volt power, I checked all the fuses in the panel box and they are all fine. I have 12 volt power working everywhere else. So, I took the AC air return cover off to trace thermostat wires up to what I believe is the AC controller. I pulled the red wire (identified as Y on the board) and blue wire (identified as B-). I believe that these are the hot and ground terminals. I used a tester and found no voltage coming from those terminals. So, I know its not the wiring to the thermostat but something at the AC itself.

My understanding is that if there is no 12 volt power making it to the thermostat this will stop both the air conditioner and heater from working.

So... what do I do now? Is there a "hidden" fuse on the AC unit itself that I need to check? If so, where is that... from inside the RV or do I go on the roof and remove the shroud up there? Is the problem the AC controller and is that the device I tested? It has the thermostat wires coming out of it and an AC 110 volt wire going into it. Or... is this still too little information with which to determine the likely problem?

I am pretty much stuck unless someone knowledgeable can chime in with some ideas. Otherwise, I guess I will have to call an RV repairman to come out... UGH.

Thanks in advance to anyone that can help me out.

I am attempting to add some pictures to help show what I checked. These photos are up inside the air return of the AC.

Jmooney · 03-29-2015, 09:18 PM

Just thinking out loud..... My A/C unit's fan only runs when on 110vA/c. ( regardless if the compressor is engaged or fan only) The blower fan from the furnace is a diffrent system all together, although both are controlled by the same thermostat

the therostate must have some power that it is switchng back to both the furnace and A/c unit , so either a seperare power source or from the furnance ..... I think

I think.....hummmm.....

In line fuse behind thermostat?

You said digital thermostat, so I'm assuming no digital display was working... Meaning either blown or no DC power

Jmooney · 03-29-2015, 09:19 PM

Pull wires behind thermostat out of wall to see if you have an inline fuse back there

Jmooney · 03-29-2015, 09:25 PM

Diffrent thread today discussed a digital thermostat and talked about fuse mounted directly to circuit board

See this link for photo

http://www.jaycoowners.com/forums/at...1&d=1426783197

newbold1 · 03-29-2015, 09:55 PM

I had the RV connected to shore power and both the furnace and A/C are still dead. The thermostat had no fuse on it and there was no inline fuse on the wiring coming out of the wall to the thermostat. I even reconnected the original analog thermostat that the RV came with and that didn't change anything.

On shore power this morning the furnace was running fine. Yesterday the A/C blower fan was running when I needed that instead of heat. Then, I get home and both furnace and A/C refuse to operate at all. Shore power is working as all my outlets, television, microwave, etc. are powered up. DC is working because the 12 volt jack by the control station works and all my lights are working even when I disconnect my shore power.

It seems the issue is isolated to only the A/C and furnace. I sure wish I knew how to fix this. I hate reaching a point and then feeling stuck. I like to solve it myself and learn from it but I guess I might have to get a repairman out here.

newbold1 · 03-29-2015, 10:09 PM

Oh... the digital display is dead except when I put batteries into the thermostat. I haven't figured out for sure whether the thermostat should power up without batteries if the 12 volt power was coming in through the wiring. I really don't know as I have always had batteries installed and never really tried it without them to see if the wiring itself would have done the job to power up the digital display.

In any case, even the old analog thermostat fails to work for me now and I know the 12 volt power supply is dead right at the A/C itself before feeding into the thermostat wiring that goes to the thermostat itself.

Now, I am just trying to figure out why there is no power at the source. Bad A/C controller? Hate to sound stupid but is that thing in the photos I took the A/C controller? Those pictures are inside the air return. I took the cover off where you normally clean the filter and this is up inside there. You can see the brownish bundled wire which leads from here through the walls down to the thermostat on the wall.

No 12 volt power here to feed that brown wire which feeds the thermostat. Makes me think A/C controller but just based on reading things about this issue.

What do you all think / know?

I hope I am describing all of this clear enough to help everyone to help me.

Thanks!

newbold1 · 03-29-2015, 11:35 PM

I found an excellent photo of the actual part where I tested for 12 volt power. Part # 8330-3851 which is called out as "Junction Box Complete" and on some sites "Control Box". In my earlier photo you see a label numbered 8330B6332 and that apparently is for the entire Flush Mount Ceiling Plenum of which the junction box is one component.

I am a little uneasy to pull that part down but am wondering if there could be a fuse in there or if the only option is that it works or else has to be replaced. In my case, I would assume replaced.

Grumpy · 03-30-2015, 06:59 AM

Quote:

Originally Posted by newbold1

I found an excellent photo of the actual part where I tested for 12 volt power. Part # 8330-3851 which is called out as "Junction Box Complete" and on some sites "Control Box". In my earlier photo you see a label numbered 8330B6332 and that apparently is for the entire Flush Mount Ceiling Plenum of which the junction box is one component.

I am a little uneasy to pull that part down but am wondering if there could be a fuse in there or if the only option is that it works or else has to be replaced. In my case, I would assume replaced.

The 12v for the thermostat comes directly from the fuse panel not from the ac unit itself. Either a bad thermostat or a blown fuse. As was mentioned sometimes there is an inline fuse in the wirirng inside the wall. Take the themrostat off the wall and pull the wiring out to check. You won't get 12v at the control box sine it is sent there from the thermostat, not from the control box to the thermostat.

tnchuck100 · 03-30-2015, 07:21 AM

Through reading all of the posts I keep coming back to a blown fuse. Now the question becomes did you check the fuses visually or for actual continuity? It is rare but if these fuse sockets are mounted on a printed circuit board (most are) there could be a bad solder joint there.

newbold1 · 03-30-2015, 03:03 PM

I finally found it and fixed it. I traced back the furnace hot / ground wires to the furnace and found them dead there at the source. It turns out that all the way on the back side of the furnace there is a switch. It seems to be like a reset trip switch sort of thing. I had no idea what the switch did but figured I would give that a try and cycle it. Voila! The A/C and heat are functioning like normal again. No blown fuses but apparently a tripped safety switch of some sort directly on the furnace itself.

Hopefully, this was just a fluke and the switch didn't trip for some reason that is going to reoccur.

The switch couldn't have been more hidden. It was on the back side of the furnace and I only found it by touching it when actually reaching for wires. Found that switch by accident. Wow!

Clayton4971 · 03-30-2015, 03:21 PM

Thanks for posting the update it's nice to know the outcome of some of the issues on here for all to learn .

newbold1 · 03-30-2015, 03:28 PM

I always figure it might be helpful to someone else that runs into the same problem down the line. I got lucky and could have instead ended up spending a lot of time and money over something as simple as resetting a hidden switch.

Seann45 · 03-31-2015, 07:05 AM

I was just going to mention that switch as I had it go on me last year.. glad you found it..

newbold1 · 03-31-2015, 08:25 PM

Quote:

Originally Posted by Seann45

I was just going to mention that switch as I had it go on me last year.. glad you found it..

I nearly did not find it because of where it was located. Funny thing is I found nothing about that switch and it was such a simple fix. BUT... without finding it I was completely stuck with a broken system.

If I had called for someone to come out and diagnose / repair... who know what I would have been told and how much I might have spent.

karentodd76 · 04-17-2017, 07:45 PM

Hi, I am wondering if I am having the same issue with the switch, my issue is the "heat" will come on for like 1 minute and blow cold air then shut right off. What do you think that is?

jefflondon999 · 04-28-2017, 01:01 PM

The switch was the answer. Who would have guessed that was there and also that it would break the circuit on the AC unit too? I was convinced it must be the thermostat but was holding out hope that there was an easier solution and I'm happy to report that there was and everything fired up as soon as I switched it from "Off" to "Reset"

I don't understand why that's there, though, and I would urge Jayco and the furnace manufacturer to document this in their owner's manuals and troubleshooting guides. This is extremely non-intuitive. It could not be in a more inconvenient place in my trailer. I had to take the stove/oven completely out of the cabinet to get to it as there's no outside panel to access the furnace and the switch is too far back to reach and in too tight of a space. It seems to me that it would be better if the fuses were allowed to work as designed as they are located to be easily accessed for just this reason.

Oh well. Back in business. Thank you to the OP! Here are a couple of pics to help you find it if you ever have the same problem (No furnace, no fan, no AC, no blown fuses or circuit breakers).

Sunflake · 04-28-2017, 08:58 PM

With your meter try checking the R terminal. This should be 12 v power.

RickAE · 05-30-2018, 02:38 PM

I realize this is an old thread. That being said, it took me a while to find it. Actually Peggy found it for me while I was in the middle of trying to figure out why my Fan, Air Conditioner and, Heater would not work. It turned out to be the hidden switch on the furnace itself. It was kicked off. I reset it and the fan came on.then We tried the A/C, it came on ran like a champ. after it recycled it quit again. I tried to cycle it again and it started but would not blow any air. I then reached in and spun the squirrel cage and it started to blow and it cooled the trailer. recycled again same thing, would not run. we are home now and I was going to check the fan run capacitor (sp.) but the weather is too rainy to get on top of the camper. I'll let you know if it is the culprit. or I'll be back for more help!! This forum is the greatest. Thank you Newbold1

RickAE · 06-02-2018, 10:28 AM

Well the problem turned out to be the run capacitor. pn 1499-546. cost me $22.00 and about 45 minutes to troubleshoot and replace.

jodie3t · 03-09-2019, 07:25 AM

Hey everyone, just wanted to add how much this thread helped us solve our heat/AC problem. We have a 2017 Jayflight 21QB and my husband was replacing the analog thermostat with the Hunter thermostat. He wrongly added the jumper wire to the thermostat and both the AC and heat quit. All fuses checked good. Fearing the worst he was afraid he shorted out relays in both units. Like the OP we were afraid to take it to a dealer to have them check it out. I finally stumbled onto this thread and our furnace has the exact same black reset switch. Ours was mounted under the jack-knife sofa. We reset the switch and everything works perfectly now. Thanks for all the great info! Jodie

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