heater on coach not working

[cheryl]

Last yr we had our back ac replaced and have not used the back heater since, however it was working fine before ac replacement.  we now are getting to need the heater some.  We have checked all we can, at first it would blow the fuse when turned on.  Checked connections and all ok.  Checked wiring on ac and all seem to be correct.  Still blowing fuse when turned on.  Any suggestions?  Thanks C

 

[Gary RV_Wizard]

You mentioned both a/c and "heater".  Is your rear a/c a heat pump type or perhaps one that has electric heat strips to provide some warmth?  The possible problems will be diferent for the two different types.

First thing, though, is to check the voltage available where you are testing this.  What type of elctrical service do you have (30 amp, 50 amp, ec) and do you have a voltage meter/monitor to check the voltage?

 

[cheryl]

Gary, it is a gas heater and yes checked the voltage and all seems fine.  Since it was working before the rear ac was replaced and not it wll not we figured wiring problem but have check that aqs well. c

 

[Kirk]

I'm not sure why you believe that replacing the rear air conditioner would effect the rear furnace. If you have a single thermostat that controls both the rear air conditioner and the furnace, there is a relay in the air conditioner that clicks when you turn the furnace on, or at least that is true for a Dometic. I have not been able to locate a schematic of the control side of the units, so I'm not just sure how that is wired. But, I do know that all that is supplied from the thermostat to the furnace is a 12V signal that goes to the circuit board of the furnace. You should be able to supply that thermostat signal with no thermostat if need be to test it. I am assuming that the fuse that is blowing is the 12V fuse that supplies power to the furnace? If so, I would take a good look at the wiring to the furnace.

Tell us more about what you have. What make of air conditioner, thermostat and furnace? The make of each is important.

 

[Gary RV_Wizard]

A gas furnace problem is a whole different story, Cheryl.  Maybe some wiring got messed up when they changed the rear a/c, but I can't think of anything that would cause the furnace to blow a fuse.  About the only place where the two may be wired more-or-less together would be at the thermostat and that depends on the type and brand of t-stat and furnace.  As Kirk requests, we need more info to be of assistance.

 

[Slantsixness]

Cheryl,

Even though your description is a little vague, I may be able to help you out.

You said the rear heater blows a fuse, therefore I have to assume that it's on the 12V system and is a fairly standard RV heater, and not a roof mounted heat pump or a diesel furnace, either.

RV gas furnaces all have an impleller, or blower fan. This fan will typically come on as soon as the thermostat relay cuts in. If this motor is frozen or bound, that would be enough to blow the fuse. Prior to the fuse blowing, the could be a hum noise coming from the heater. The noise would be more obvious outside the RV. The motor could have gone bad and froze up, or you could have varmints or a mud wasp nest in the heater ports.

Some heater have both a blower motor and an evacuation motor. The evacuation motor also comes on as soon as the heater starts up, and yes, it would blow the 12V fuse too. This motor is actually more "outside" the heater (right behind the heater exhaust port outside the RV).

Lastly, if the Fans actually come on and then the fuse blows, your propane ignitor could be shorted out.

What to do:

First:
Are you, or a handyperson working with you, confident and comfortable about working with propane RV appliances?

Turn off the propane at the mains. To remove most of the gas pressure, you can light your cook stove then wait for it to go out with the gas off. That's a pretty safe bet.

Typical inspection and cleanout:
Remove the heater cover on the ouside of the RV, usually 4 to 6 screws. Pull the cover off (there may be a small amount of sealer between the cover and the RV body, but it will let go with a little tugging). Look into the exhaust and intake ports for evidence of a blockage.? If you see something (typically mud wasp nests) you can clean out what you find with a small scraper (I recommend plastic) and use a shop vac or vacuum of some kind to remove the debris. In a severe case, the intake/exhaust and impeller may have to be disassembled and cleaned. If you can't get it all cleaned out, have a qualified service technician do it.

Ignitor service:
If the fans work, and there's no blockage or bound motor(s), you may have to replace your ignitor. There are several types, from hot anodes to Direct spark types. Sometimes the ignitor comes with a new circuit board (direct spark) or just the anode. the ignitor is usually located in the heater fairly close to the gas inlet, and most, or at least the wires to them, are Red or Orange in color. Unless you are very confident, I would recommend that this just be checked by you, replacement would be best by a qualified service technician.

After you have repaired or cleaned your heater, then replace the fuse and try it "with the Gas still OFF" the heater will run without gas applied, if it does run, then you will have the confidence to turn the gas back on. Do not run the heater with the outside cover removed! (it may not even run if there's a safety switch behind the panel, too)


I hope this helps you, I could elaborate more on this if I knew the exact model of heater you have. This is on a small label on the heater near the gas inlet to it, so the cover would have to come off, at the least....

be safe, be careful

Tom