No heat

Help! No Heat, No A/C, No fan. Not sure what to look for. Thermostat buttons function but A/C will not go on. Changed mode to furnace, blower will not go on. Change mode to fan, fan will not go on.

Fireplace heater working as are other electrical outlets. Water pump, hot water heater (propane), lights all working.

Ideas????

Not an expert by any means, but have you checked the breakers?

Hi Jeff,

First, check the voltage on the 12V DC system to make sure you have 12V. You could check with a voltmeter at the fuse box. If your entry door has contact pins on the inside door jamb, that's another location that's easy to check.

Next I'd remove the thermostat cover and look for loose wires. Remove the thermostat from the wall if necessary.

If that all looks good, next place to check would be in the living room A/C unit. There's likely a relay box that the thermostat connects to in order to signal the A/C unit or furnace to start up.

olcoon said:

Not an expert by any means, but have you checked the breakers?

Click to expand...

Yep ... nothing tripped on the A/C side and no red lights on the 12v panel.

Hi Dan,

Okay a pulled out my meter to check the voltage at the fuse box. Didn't get that far. I pulled out the bottom fuse and the red light came on next to that fuse. I plugged it back in and the furnace kicked on when I did that. Doesn't give me a warm/fuzzy feeling as I'd like to really know what the problem is.

At least we will be warm tonight in Fort Stockton ... 20 degrees with a wind chill of 11. We didn't plan to stop here but with high winds along I10 we thought it would be a safe bet. Went and bought two small heaters to keep us warm just in case I couldn't get the furnace working. Will keep them now for backup.

Make sure you don't put them into the same circuit.

Glad you got it working, although the fix seems a little problematic. Hope you have some spare fuses on hand.

Have you tried changing the FAN mode to HIGH or LOW to see if that's working now?

azbigfoot said:

Hi Dan,

Okay a pulled out my meter to check the voltage at the fuse box. Didn't get that far. I pulled out the bottom fuse and the red light came on next to that fuse. I plugged it back in and the furnace kicked on when I did that. Doesn't give me a warm/fuzzy feeling as I'd like to really know what the problem is.

At least we will be warm tonight in Fort Stockton ... 20 degrees with a wind chill of 11. We didn't plan to stop here but with high winds along I10 we thought it would be a safe bet. Went and bought two small heaters to keep us warm just in case I couldn't get the furnace working. Will keep them now for backup.

Click to expand...

I just had an almost identical situation with our Cyclone. The Thermostat and 3 12v Fans all were dead even though they had been used recently and the trailer not moved since.
Since the thermostat was blank, neither A/C or Furnace would come on.

Checking everything in sight showed no problem with breakers, fuses, relays etc and -all- other 12v systems worked fine.

I contacted HL Cust Service and was arranging for a mobile Tech to work on it but decided to do some final double checks. I flipped and reset all breakers, pulled and reinserted all fuses.
Finally after a lot of fiddling the problem disappeared and everything worked! You are right, it does shake your confidence in the wiring, but at least it is resolved, for now.

While working on this problem I used a tool that has proven repeatedly to be the most valuable one I own... Power Probe 3. This tool can seriously facilitate diagnosing a 12v wiring problem, even for a novice.

I would remove the 12V panel and inspect the wiring connections at the back of the fuses. Maybe 1 or 2 of them might be a little loose need a little more crimping.

Does the bedroom thermostat turn on the front A/C? If so, switch the thermostats, they just plug in and are identical. That will tell you if it's a thermostat issue, or if you need to look elsewhere.

azbigfoot said:

Hi Dan,

Okay a pulled out my meter to check the voltage at the fuse box. Didn't get that far. I pulled out the bottom fuse and the red light came on next to that fuse. I plugged it back in and the furnace kicked on when I did that. Doesn't give me a warm/fuzzy feeling as I'd like to really know what the problem is.

At least we will be warm tonight in Fort Stockton ... 20 degrees with a wind chill of 11. We didn't plan to stop here but with high winds along I10 we thought it would be a safe bet. Went and bought two small heaters to keep us warm just in case I couldn't get the furnace working. Will keep them now for backup.

Click to expand...

I would suggest inspecting it real close and check the wiring on the back and the terminal crimps. I found some terminal on my Cyclone that weren't crimped and had some heat damage. I would also suggest replacing the fuse even though it looks good. Had a problem with a JD tractor several years ago that I found to be a intermittent fuse even though it looked good.


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I want to post a big thank you to this thread. I arrived at our campsite yesterday afternoon and finished setting up just before the very cold rain began. Once inside I turned on the furnace and waited for more than 15 minutes. Nothing! I checked everything I could inside but still nothing. I decided to wait until today when the rain stopped to investigate further. Following all the sugestion threads I ended up at the circuit board above the furnace. I could see nothing wrong but when I repositioned the wiring harness then all of a sudden the blower came on. I checked all connections but none were loose. The circuit board is not bolted tight but is still secure. I did not want to try anything else so I secured the harness of wires with tie wraps to immobilize them from bouncing around. As a heads up, the 6 screws holding the chrome exhaust plate to the outside cover are smaller than a #20 torx. I was able to find a #15 torx (slightly smaller than correct) and got them out. You have to come in from the outside wall plate to get to the circuit board above the furnace. I have a Cyclone 3110 with a Suburban furnace. As they say, you can't fix it til it's broke. So I will be ready next time and save an hour of trouble shooting. I am suspecting a possible circuit board issue. My warranty is over so I will pick up a spare board for the future.

I was able to discover that the fireplace heater and two oil filled radiator heaters did a good job of keeping the chill out of the RV. I ran all 3 heaters at 750 watts each so to not press my luck with the breakers. However, the furnace is now keeping everything toasty inside.