# Dead Thermostat - Any Ideas?



## chrispmeyer (Feb 23, 2014)

Hi All - We have a 2014 301BQ, 25k miles on it and we love it. Today I replaced the two golf cart batteries as they were dying (poor maintenance on my part). While reconnecting I crossed wires and tripped a fuse in the box. I also seem to have killed my thermostat and the controller for the bed that raises the head up and down. The thermostat is just blank, so I can't run the main a/c or the heater (and I'm with my family in CO where it was 35 last night). I have a suspicion it's a fuse somewhere given the bed is also out but am out of ideas on where to look. The fuse in the thermostat itself (Coleman Mach Digital which I added earlier this year and love!) is fine. Pilot light is out, reefer working, and rear a/c works. Any ideas on places to check before I wrap the kids in snow suits at night or call the mobile repair service? Thanks!


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## Leedek (Nov 28, 2010)

If you have a Volt Ohm Meter you can trouble shoot the HVAC and thermostat. The PDF below is for the most common Mach thermostat. The diagnostic flow chart can be a great source of troubleshooting.

View attachment 12 volt thermostat Coleman 8330-3362.pdf


The biggest clue you have is what happened prior to your problem? You crossed the battery wires. That zap may have (probably did) tripped your *Short Stop breakers* on the frame rail/tongue rail of your trailer. These two breakers are there to protect your converter when heavy current shorts happen. If you follow the wire from the battery box it will soon encounter two breakers. They will have red rubber protective caps on top. When they trip it is the same as turning off your 12VDC. They are supposed to be auto reset but it's possible they did not reset and need to be replaced.

Good luck and remember...* BLACK IS HOT (POSITIVE)*

* WHITE IS NEUTRAL (NEGATIVE)*

NOTE: In the photo below the installer placed the Short stop breakers inside the battery box

*







*


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## chrispmeyer (Feb 23, 2014)

Thanks, Leedek! I've had quite the adventure with my electrical system this week traipsing across CO. This forum, as per usual, has been really helpful. I'm pretty sure my stupid battery re-N stall was indeed the problem. When we bought the 301BQ, I had them install twin 6V golf cart batteries. When I replaced them I totally spaced on polarity and wiring in series, like an idiot. Got that sorted.

I think that actually fried the thermostat. I remembered that when I swapped in the new digital one earlier this year, I tucked the old one away in a cabinet. Tracked it down, installed it and good to go. That's when the fun started...

On 50a shore power, things were running fine (except for the power bed in the bedroom). Reconnected the batteries black to hot, negative to positive in second battery, and negative in second to the white). Feeling great, right? About 5-6 hours later, I hear a loud pop. Everything still running, so I kind of write it off after not finding anything. Take the family to the rodeo down the road, come back a few hours later and nothing. No power to anything 12V: lights, slides, awning, electric jack. Nada. Freak out time.

I start rifling through all my owners manuals trying to figure out the manual override for slides & awning while in parallel power searching forums here to see what I can learn. Come across a couple of discussions about revering polarity and popping converter fuses. Maybe that's my issue. But where is the converter??? Look all over (in the rain at 1100pm) outside and in trying to find the the secret hiding spot. More searching leads me to a clue that it's next to the circuit board. Disassemble and remove that, lo and behold there it is. Get my wife to use her smaller hands to pull out the two 40A fuses ( what a hassle!) and discover they're blown. Replace and everything (including the bed!) works when I power back up on shore power. All good I think.

Today I reconnect batteries and an hour later I hear a noise from the circuit box/converter area. Never heard it before. Sounds to me like a fan running hard. My wife also smells sulfur. I have flashbacks and am thinking that could be what caused the pop. take a guess and disconnect the battery - fan shuts off.

So, I seem to be in a place where 50a shore with no battery works fine. Battery with no shore power works fine. Where does that leave me? I'm thinking it must be a bad converter - maybe I screwed it up with my terrible battery re-install? Would love any ideas y'all have as I'd sure prefer to fix it myself than haul it to the dealer.

Thanks again!


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