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Randall, RVIA Certification
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Have an Atwood Model 8525-IV-DCLP-LD furnace in my Aljo pull

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Have an Atwood Model 8525-IV-DCLP-LD furnace in my Aljo pull trailer. It has worked fine but after a recent hunting trip, found that the "internal fan" (Not circulation) runs continually. Finally disconnected the thermostat and it still runs. Only way to shut it off is to disconnect red and black wires to motor (or of course power source 110 or batteries). Furnace still seems to work fine otherwise. It was cold where we were hunting so we added batteries in parallel and did lots of charging. Did not notice problem until we gone home. Your thoughts please.
Hi: Thank you for coming to Just Answer with your question. My name is XXXXX XXXXX perhaps I can assist you with this issue.

If these were all 12 VDC batteries that are in parallel then you should be fine there. When the fan motor won't stop except for taking the fuse out this is usually a case of the timed delay relay going bad............unless you have a later model that has the relay on the control board and then you need the whole board. Go HERE for a copy of the Service Manual on this unit. I would print out a copy so you have it. Notice the section where it shows the timed delay relay. If you don't have one then you have the later style with it on the board. That control board has an LED on it for trouble shooting. Most shops will carry the relay. They aren't that expensive. If you have the board tested and it is bad then I would get a replacement made by Dinosaur Electronics as they are far superior to the OEM boards. It is called a "Fan 50 Plus" if you ask for one. Carefully mark the wires where they go on the relay if you have one so you can get them back on where they came off. Don't forget to have the LP pressure tested at the regulator at least once a year. Low LP pressure, especially in cold weather can make the furnace operate erratically.

Get back to me if you need more help with this. Multiple responses are fine and expected and included in our fee which is paid from your deposit upon acceptance of any answer. Follow up questions are included as well. R.J.
This should have an outside inspection panel that you take a couple of screws loose and the door folds down to access the relay and the control board on the far L/H side. Take the wing nut loose and it pulls out towards you and you just unplug it. R.J.
Customer: replied 5 years ago.
Will get back to you after checking out your suggestion
Bookmark this and you can return to it at any time.............R.J.
Customer: replied 5 years ago.
It may take a day or two to check this out. I am 1000 miles removed from the unit right now. I will pay you but I might have some more questions after my son checks to see if we got the correct unit
Not a problem.............just Bookmark this and come back to it anytime. The easiest way for him to see if it is the relay if you have that version is to turn off the thermostat and if it won't shut off go out and see if there is still current through the relay. If the relay is "stuck on" then it will stay on. They can also be tested at a shop. R.J.
Customer: replied 5 years ago.
If this relay is "stuck", I can understand the combustion circuit continuing but if it is "stuck", how does it move on to "ignite" if you turn the thermostat up? The furnace seems to function normal, it just the combustion circuit that seems to stay on.
If it is "stuck on" when you put the fuse back in the furnace should start after about 10 seconds. First determine which model you have. One has a separate relay and one has it on the control board. The result is about the same. The repair cost will be quite a bit different............the one on the board will be about $160 as opposed to about $20 for the one by itself. R.J.
Randall and other RV Specialists are ready to help you
Did this have a panel on the outside you can remove to access the furnace where the intake and exhaust is? Some are held on with 4 screws and some have two larger flat headed screws that you turn to allow it to fold down. Once you can access this you can get to the area for the control board and take it out to be tested. If it has the relay separately, you can take it off as it is right there as the manual shows. If you can do this yourself it will save you over $100 I suspect. Get back to me if you need more help with it.
Customer: replied 5 years ago.
Would the fact that we charged the batteries once or twice a day from my pickup which has a 100+ amp alternator change your thinking any? I suspect that at times the heater might have been running while we were recharging the batteries.
That shouldn't affect it if the battery in the trailer was in good shape. The furnace can operate at higher than 12.8 VDC and not damage it. Relays go bad...........not unusual considering the age of the coach. And easy enough to get to and check............R.J.