Suburban Furnace problem

[Russell E Johnson]

I have a Suburban furnace in my 87 Southwind. It will not produce heat. The sail switch is working, as is the high temp sensor and the propane tank is full. It was working fine, but then just quit producing heat. Any suggestions as what to look at next?

[Rich Thomas]

I have been working on mine as well, I don't want to insult you so please take this with a grain of salt. on your fan and limit switches take an ohm meter and and test continuity by holding the bi-metal disk over a light bulb to make sure they are actually opening and closing under the heat of the light bulb ( normal operating conditions ). the sail switch can be tested in place. if your furnace has the old ignition board with the time delay built into the board (like mine) it will have a physical relay called the thermostat relay in the upper left corner of the furnace housing it looks like an old voltage regulator. pull this off the furnace and test with an ohm meter across pins 1 and 3. If they read open you will have found your problem. this is the time delay coil that  puts power back to the ignition board. also you may want to try to read continuity in the coil wire that goes to the ignite-r probe( it looks like a spark plug wire. My time delay relay had an open coil wire so it is in transit from an E-bay seller. they are no longer available through dealers. I hope this helps you out.      

[Russell E Johnson]

Thanks Rich, no insult taken, all advice is greatly appreciated.  I did my testing connected to power and got 12 volts on both sides of the limit and sail switches.  When I get the MH back from the repair shop--burned up new starter (heat shield not reinstalled) and both headers leaking (not tightened properly)--I will try your suggestions.

[david craft]

By your saying that the gas valve is good, are you saying your testing 12 volts or better at the valve as produced by the ignitor board?(never test with a test light at this point because of possible board damage) by the symptoms you described, you should be smelling gas out the exhaust with a functional valve and no spark. Turn off the gas then disconnect the ignitor lead off the probes. hold the ignitor lead 1/8 inch off grounding surface and verify spark from board during trial run (i.e. 20 second delay after fan run). If you have spark but no spark through probes, try cheaning carbon off insulators and try for spark through probes again. If still no spark through probes the you have cracked insulator...replace probes.

[John "T" Nordhoff]

 I'm late here but the only thing I might add is those Control Boards are voltage sensitive and will NOT work if their supply voltage and/or house battery voltage is much below the 12 volt threshold. Ive see instances where low batteries would allow the t stat to be satisfied and blower start and sail switch close BUT THE IGNITER NEVER LIGHT......Then if plugged to shore power so the converter charger raises the voltage they will work........Just sayin

 John T

[Russell E Johnson]

I have tried it both ways, voltage level is not the problem, but thanks for the insight.

[Rich Thomas]

Just wanted to give you a little hope on you furnace. I got mine up and running today it was the relay I mentioned before $ 34.00 off ebay hope yours is a simple problem as well.

[david craft]

Ive seen that before john...the gas valve draws enough current where the board would actually drop out and would require a reset. Did we ever get this working??

[Russell E Johnson]

No, David, I have not had the MH for the past month, it is in the shop where they are working on the cruise control and trying to find a short in the dash that keeps blowing the fuse.

[Russell E Johnson]

I don't know what happened, but half my message disappeared, so here is the rest of it:

After I get it back from them I will start in on the furnace again.  I will also be installing a tankless water heater, my DW gave the go ahead on replacing the water heater instead of fighting to repair it, YES!  All this needs to be done before we leave for Arizona the end of January.

[david craft]

Shucks...actually im weak on chassis preferring long ago to just do coach work...too hard on the lower back. Regarding the furnace...you might just take inthe board and have it tested. I test them for free...if they are good that is. If they are bad and they buy a board from me its free too. If its bad and they dont buy from me its 10 bucks...lol. Maybe you can find the same deal...get a dinosaur brand board if you do get one...3 year warranty

[Russell E Johnson]

David, where are you located?, I could use a good coach person.

[david craft]

In the redding area of norcal. In regards to the tankless...i havent seen a design imsold on yet. Let me know what model your looking at so i can talk you out of it...just kidding! Ive worked onn them back when i first started...junkers and the jack rabbit brands. The last one i put in...the new fangled RV one, was pretty sophisticated. It was built to replace an RV water heater with matching dimensions even. First off, i didnt like the bottom pan area. Rain could get in the door area and it was not really sealed or sloped to drain. The freeze protection was over the top. Once temps got down to freezing, it would fire up, cycle a little water and shut off. The cycled water was plumbed back to the fresh water tank or on the ground ..your choice. Problem with that? Plenty! If you lose water pressure, 12 volts, or propane she'll freeze quick!! Any one of the 3! That copper heat exchanger was made for rapid heat transfer and shes sittin' outside. With all them fins...she aint no easy patch. Our sales department next door sold the guy on the tankless design so I installed it for him..and yep...I have already done one replacement core for him. Look that thing over dang good and ask all the right questions before you get one. Of Course I fix em' for a living...so I'm always thinkin' worse case scenario...shootin' down thinkin' and rainin' on parades..hehe