Problem with Atwood furnace

[DonMichUP]

Hi everyone. I have an Atwood 8516DCLP in my 1999 Alaskan Camper that worked wonderfully, but then all of a sudden stopped firing up. Fan would blow (common thing with the circuit board it has) but no ignition sound. I was going to trouble shoot the solenoid gas valve coils, and then the sail switch... considering that 75% of circuit boards are not faulty and replaced for nothing... and realized that I'd have to access the furnace from the inside of the camper so began taking cabinets and compartments apart. Good thing I did.

On the camper wiring that goes to the furnace, along with the thermostat wires, is a white wire that attaches to a yellow wire and then a plug connection. Alaskan says that the white wire is ground. From there the wiring goes to the furnace. The yellow wire's insulation was melted, exposing bare wiring. Good thing there wasn't a fire! I've included some photos. The furnace is only runs off the inverter from 120V shore power, no battery connection.

Any idea what might have caused this?? I'm at a loss. And after seeing that melted wire, pretty concerned. I see that the wiring was damaged after the wiring clamp, but not before that. So I 'do' wonder if that has something to do with it(??).
Don

[DonMichUP]

Yeah, they sure were helpful. I do have some 4/0 and 2/0 cable laying around not being used, but that's overkill. The new board has a fuse on it, and if I remember correctly, Joe said that that should prevent the problem I originally had with the ground wire getting too hot. Unless some dummy in the past did indeed wire a battery backwards to the 4 pin 12V inlet on the Alaskan. Regardless, I'll keep an eye on things.

[enblethen]

The owner of Dinosaur is a former NASA engineer. He is quite often the one individuals talk to.
Some of the high tech audio installers may have a similar wire.

[DonMichUP]

Bad news: the wire from West Marine is back ordered 28 days, so I cancelled the order. They were nice about it, but now I'll have to find another source. The good news: I HAVE HEAT!

As mentioned before, the usual parts checked out ok, as did the board. But I replaced the motor, sail switch, electrode, and burner gasket anyway. I couldn't get the limit switch out because I didn't have a small enough square bit, so have one as a spare now. I then replaced a section of the wiring with appliance wiring rated at 105c. I also bypassed the molex connector, and applied duct tape to the sharp edges of the furnace case to prevent abrasion/cutting of the wires.

After all that, the furnace still wouldn't ignite, so I called Dinosaur Electronics and asked if a board could test good but still be bad. GREAT people!! Joe there walked me through some tests with my multi meter, and sure enough, the board was bad. So I ordered a Fan 50 Plus Pins from Amazon and paid an extra $10 for Saturday delivery (today).

I connected the wiring as per the instructions -- which were a bit confusing because my old board didn't have "power" and "blower" connection terminals on it -- but I got it right and now I have heat :).

I know this is a bit lengthy, but hopefully it will help someone else who may encounter a similar problem. #1 solution is that, yes, a bad circuit / ignitor board can test good. Joe said if the person testing the board had wiggled the wires around some, they probably would have seen that it was bad.

I want to thank everyone for their input and suggestions. It has helped a lot, and this experience has helped me maybe help someone else some day :).

[DonMichUP]

Ok. I just ordered 64' of that 10G from West Marine. Thanks :.)

[enblethen]

Your wire got close to or about 500 degrees C to melt the way it did. That is why I feel it was a severe overload and not loose connection.

[DonMichUP]

Ok, but NAPA's wire is rated at 121C, 250F... so...??? Btw, the old wire was rated at 105C, 221F, and it melted.

[enblethen]

The majority of XLPE is either 7 or 13 strand.
I would look at your local marine supply for some like this. Yes, a little more expensive but much more flexible. Rated 105 degrees C.West marine

[DonMichUP]

Well, I have the parts. Now to get it all together! Having a hard time finding wire though. I want to go 10 AWG, XLPE (cross-link/Polyethylene, aka "thermoset" insulation). I cannot find anything around 100 strand though. The best I can come up with is "50' solar cable Bulk Black copper #10 AWG 1000 volt PV Wire with Tough XLPE insulation" on Amazon, and it has only 19 strands. I did see on NAPA's website that they have a 10 AWG primary wire, but I can't find out if it has XLPE sheathing nor how many strands it has. It's rated to 250 degrees though, so maybe? It's located here. Your thoughts enblethen? Chum lee? Anyone? 🙂

[DonMichUP]

Thanks for the advice enblethen and Chum lee, I'll keep that in mind :).

[Chum_lee]

enblethen wrote:
Need to be careful as to what insulation is on the conductors.
It needs to be high temperature rated multi-strand wire. (Not building type stranded, should be around 100 strand)
hard to find these days is true appliance wire.
Thermoset insulation would be better then thermo-plastic.

Yes! Very true. Any decent auto parts supply store will stock exactly what is needed. NAPA, trailer supply etc. are good places to start. Home Depot is not.

Chum lee

[enblethen]

Need to be careful as to what insulation is on the conductors.
It needs to be high temperature rated multi-strand wire. (Not building type stranded, should be around 100 strand)
hard to find these days is true appliance wire.
Thermoset insulation would be better then thermo-plastic.

[DonMichUP]

Thanks for chiming in Chum lee. Nice to hear from someone who has had the exact same problem. I'll for sure plan on replacing to lower gauge wires. I might as well replace the hot too, since I only have 2 wires anyway -- a hot and a ground.

[Chum_lee]

I had the EXACT same thing happen to my Atwood furnace. It looked to me like the yellow wire at the multi-point connector was under size and burned up starting at the at the connector due to excessive resistance. Exact same symptoms as you. I replaced/rerouted the yellow wire with 12 gauge wire and the problem went away. I didn't use the multi-point connector for the yellow wire but instead installed a separate spade connector. If I remember correctly I also replaced all the ground wires with 12 gauge wire.

Chum lee

[DonMichUP]

That seems like the logical answer road-runner. The "Field Plug Assembly" is another molex connector of course, but hopefully it'll do ok. Maybe I should apply some dielectric grease? I'll also make sure that the clamp isn't holding the wires too tightly. Instead of the molex connector, I was considering just joining the wires using butt connectors. But, the entry into the furnace where the molex was and is supposed to be has sharp edges, and that would eventually wear through the wire insulation. Good luck with your water pump problem. Sometimes I think they put too small of wire gauge in these things. I'm considering using a thicker gauge from the inverter to the furnace actually.