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Randall
Randall, RVIA Certification
Category: RV
Satisfied Customers: 10548
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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I have an atwood model 8531 furnace in my rv. It will run

Customer Question

I have an atwood model 8531 furnace in my rv. It will run off of battery but not generator. I've replaced the motor twice, then found out it might be a relay. They've sent me 3 relays none of which are the right ones. They keep telling me the relay no longer is available and this is the replacement one. It has a ground wire, my original does not. any ideas?
Submitted: 10 months ago.
Category: RV
Expert:  Randall replied 10 months ago.

This is a 12 VDC unit and so the generator has no real function here other than charge the batteries via the converter system. I doubt that you needed two motors as one of these usually goes quite a few years, even with lots of use. Dinosaur Electronic makes a good timed delay relay for these. If you have an outside inspection panel, this is pretty easy to trouble shoot with a 12 VDC test light. About $5 at most hardware stores. I am adding a link to the Atwood Service Mnual for this model. Print out a copy as there is a lot of good information in there. IF the motor comes on when you ask for heat, it isn't the relay. You can hook up the motor directly to a 12 VDC power source and see if it comes on or not. Get back to me if you need assistance with the testing. All follow ups are included in our fee. http://bryantrv.com/docs2/docs/hflamefurn04.pdf

Customer: replied 10 months ago.
I already know the converter doesn't supply power to the heater, only the battery does. But every time I hook up the generator or house power, it blows my 10 amp blower fuse at the converter. But if I just hook up my battery it runs the heater just fine.
Customer: replied 10 months ago.
I already know the converter doesn't supply power to the heater, only the battery does. But every time I hook up the generator or house power, it blows my 10 amp fuse at the converter. But, if I just hook up my battery power, it runs the heater just fine. any ideas?
Expert:  Randall replied 10 months ago.

The converter may be shorting out and most converters work on two 30 amp fuses. You can test it with a meter. A good converter should put out about 13.7 VDC. Be sure that the house polarity is correct. It won't make a difference in the house plug, but it will in the RV. That, too, can be checked with a meter. I thought this had a time delay relay issue?

Customer: replied 10 months ago.
I replaced the converter with an updated model with reverse polarity protection. It fails on the generator too so I'm sure it's not anything to do with the house polarity. I don't know what the issue is, I'm just assuming it's the relay. That's why I've paid to ask someone to help me figure it out.
Expert:  Randall replied 10 months ago.

Get a test light or meter and this isn't hard to do. Does the motor come on or not when you ask for heat?

Expert:  Randall replied 10 months ago.

What is the 10 amp fuse you are blowing? The heater is supposed to have a 15 amp fuse. the reverse polarity fuses in the converter are either 30 or 40 amp.

Expert:  Randall replied 10 months ago.

Did you print out the manual I gave you?

Customer: replied 10 months ago.
It Depends on how I try to operate it on whether it works or not. Like I said before, it operates just fine if I have it running on battery power. If I have it operating on generator or house, it blows the 10 amp fuse. Most do run off of a 15 amp as you said, however mine requires a 10 amp and has as long as I've owned it. It specifically says 10 amp on the fuse box cover. I already had the manual printed out, so yes I have the manual. None of the wiring diagrams in the manual match the model I have.
Expert:  Randall replied 10 months ago.

I don't see this going anywhere so I will opt out of the question. I have fixed over 100 of these over the years and see this question almost every week here. You don't seem to want to do what is required to solve this and you probably have to take it into a shop. Sorry it didn't work out. I will put your question up for another tech to offer something if they want.

Customer: replied 10 months ago.
I'm a little confused here. How are you coming to the assumption I'm not willing to do what is required? I've answered all your questions and your information has not been helpful to this point. You keep telling me I need a 15 amp fuse when I tell you it clearly requires a 10 according to the original diagram on the fuse box. I've checked everything you've asked, already prior to my asking for your help. But your right, you've been of no help at all so give me someone who can help. wasted my time and my money so far.