Thermostat not getting 12v

[KotzurJ]

Hey guys, first post just recently started full timing in a 2004 KZ inc. New Vision 34’ 5th wheel. Everything worked great until last week, the a/c started short cycling and the LP leak detector started screaming and showing a fault. I replaced the thermostat which changed nothing big surprise. I can’t seem to figure this out. I test for voltage at the thermostat and I’m getting 1.67v so I’m figuring loose connection somewhere. I bypassed the leak detector thinking that was causing an issue but it didn’t solve anything. Breakers are alll fine, fuses are good, we are connected to shore power. No other power issues only the thermostat. I’m searched but couldn’t find anything already posted. If anyone has any ideas please let me know. I have a Coleman Mach cool/heat slider thermostat, a airxcel rooftop ac, and I don’t know what brand of furnace, it’s right beneath the stove if that helps. Coming into winter just trying to get this furnace burning.

[KotzurJ]

For some reason the images are only opening on my posts if you open them in a new tab. Atleast from my end, I'm not sure if they are showing up for you guys.

[KotzurJ]

I pulled the Furnace out and I am only reading 1.8v on the blue wires. I flipped the switch and attempted to start the system again but it did not start up.

[CA_Traveler]

IF these are 12V power wires then what is the voltage of each one from a good frame ground? A wire tracer can be very helpful in tracing wires.

[dougrainer]

KotzurJ wrote:
The Furnace is a SF-35f Model number

This particular Model requires you to remove the furnace for troubleshooting and repair. It does NOT have the Outside access door. BUT, Since the Oven is on top, it would be easier to remove the Oven assbly to access the 4 wires at the furnace. You are looking for 2- Blue wires. One of the blue will have 12 volts. Makes no difference which one. Just test BOTH for 12 volts. IF no 12 volts, the furnace 12 volt power fuse or reset switch is tripped. The furnace has a black small On/Off switch in the outside casing. This will usually trip if you shorted the wires when replacing the tstat. The Oven only has 4 or 6 screws holding it in and the LP gas line which you disconnect. Turn the LP OFF at the tank first. Doug

[KotzurJ]

I tested the power supply going into the Furnace, which is a white and black wire similar to the wires supplying the light fixtures and outlets with power. The wires were reading 1.8v So I am guessing that the issue is before the furnace. I do not know where the wires come from thought so that is the new issue. Any ideas?

[KotzurJ]

The Furnace is a SF-35f Model number

[CA_Traveler]

deleted

[KotzurJ]

The Furnace stickers just say Suburban Manufacturing company Dayton, TN 37321. Direct vent system appliance.

[KotzurJ]

Theres the Thermostat and the wires, I copied the old thermostats wiring . I will remove the furnace cover and post a picture whenever it is done. Thanks! I also have a battery hooked up currently and it is not making a difference.

[dougrainer]

1. The wall tstat will NOT cause short cycling
2. You HAD to have miswired the new Tstat
3. Some RV makers use the 2- FURNACE 12 volt wires that go to the Tstat to POWER the tstat.
4. Now for some fun with you. I don't know what engine I have in my car but it is located beneath the hood, Hope that helps:B
5. Really need brand and model of furnace. Because some models have a 12 volt circuit breaker that will trip if you shorted those wires when replacing the wall tstat. Can you reinstall the original wall tstat, if you remember or wrote down the wire color codes? Doug

[dougrainer]

corvettekent wrote:
My Thermostat uses AA batteries. Have you checked to see if yours does also?

RVP Tstats do not use batteries.

[corvettekent]

My Thermostat uses AA batteries. Have you checked to see if yours does also?

[KotzurJ]

The camper didn’t have any batteries whenever I got it, and I haven’t put any in. The ac and heat were working great for the past couple months. I tried putting a battery from my truck and hooking it up but it didn’t change anything

[way2roll]

Are your batteries charged? Just because you are on shore power does not mean your batts are good and charging. All your 12v items run on batteries, not shore power - despite being plugged in.