Atwood RV Furnace will not start after changing propane cyl

First let me thank everyone for their response and input. It is great to always know you can get such help and assistance from RV friends.

No, I have not gotten to the bottom of our furnace problem YET! However I am convinced we will resolve the issue with your continued assistance.

I have taken most of our RVision's 8226 Trail-Lite apart and have found nothing significant, but a few interesting issues. Everything works normally except the furnace, Atwood 8531-IV-DCLP, and the Propane LP Detector, Atwood Protechtor series 2001.

(We have a 30 amp Internal Surge Guard)

I thought the LP Detector, which had malfunctioned for several days, had failed and had purchased a replacement, Atwood model 36719 LP_DOW. I installed the new detector and it did not work, 12.4 vdc and correct polarity. I thought it was DOA, called Atwood and they said to return it. The concurrent problems with the furnace, the detector coupled with your inputs made me curious about the low DC voltage. I hooked the old detector to our Wagan Power Dome EX and it functioned properly. The DOA new detector also functioned as designed when tested in the same manner.

(According to Atwood "this alarm has a seven year life." It also has an end of life mode and states it must be replaced after it has been powered for 7 years +/- 128 days. Had any of you heard of this? Does it apply to the series 2001?)

I then pulled my 12 volt battery and it tested at 13.85 volts, but I was only getting 12.45 volts to the Detector. Next I started checking out the DC portion of the Power Supply/Converter.

It is a Parallax 45 amp, series 6300, model 6345. It has nine(9) DC lugs fused at 15 amps each. The first six (6) are unfiltered and the remaining three (3) are filtered for accessories such as the stereo and such. The furnace and LP Detector are connected to unfiltered lug #5 which is at 12.25 volts with shore power connected. (All six of the unfiltered measure the 12 25 volts with shore power and 12.45 volts without. The three (3) filtered lugs measure 13.81 with shore power and 13.0 without. The LP Detector works properly when connected to one of the unfiltered lugs. Tomorrow I will connect the furnace and LP Detector to this lug and see what results.

Is this voltage drop between these lugs normal? What would cause this drop? Have any of you upgraded your power supply/converter? What do you recommend? The 45 amp has been discontented. Can you upgrade using the 55 amp?

Our thermostat is a Duo-Therm analog by Dometic number 3107612.008 0212. It controls our furnace as well as the air conditioner and the fan, auto & speed. It appears to operate on 7.5 vdc? Do you have any experience with this unit. How do you check it out or troubleshoot? Is there a remote relay associated wit it? I have not found any relay associated with the furnace, only the ignition control board?

Again, thanks for your help and advice!!!

Best wishes to all for 2013

When I read the subject line I was thinking "Excess Flow Valve" on the propane too but...

THE BLOWER WILL NOT RUN

The first step in the ignition sequence, even before the solenoid valve opens turning the gas on, is the blower First it runs, comes up to speed, sails the sail switch THEN gas is called for.

So, we have one less thing to check, We know it is not a propane issue since propane is never called for.

From the op's descripton it can be only one of two things.

1: The thermostat (This includes the wires that hook it up)

2: The furnace controal board

IF, and I stress IF it turns out to be the control board.

Dinosaur boards make first rate replacements, better in my not very humble opinion than the original, and less than half the cost.

snowdance wrote:
X-2 what eHoefler said. Turn propane off and on again very slow.

His Water Heater and Stove/Range work. So this would NOT be the problem. Doug

X-2 what eHoefler said. Turn propane off and on again very slow.

Check and make sure the propane cylinder has propane first. Then see if you can get the stove to light. If not, close the propane valve, remove the hose. Re-install the hose, slowly open the valve. Opening the valve to quickly can trip the OPD, ( Overflow Protection Device ) causing no flow of gas. Go back and light the stove, this may take a bit of time to bleed any air from the lines. Use a match or one of those butane lighters instead of the ignitor on the stove. When you get a solid steady flame, try the furnace. It should light, it may take a couple of tries to bleed any air.

My guess is that the furnace stopped working, and then you tried changing the cylinders, and then found it is still not working.

So why did it break? If the fan is not coming on, the two logical things to check are +12 to the furnace. The second is the thermostat letting +12 volts go to the furnace to tell it to start? A blown fuse in either location can prevent this.

If you know about wiring, then pull off the thermostat, and short the red and white wires. If the furnace starts, the the thermostat is probably the problem. If it does not start, then it can still be a blown fuse to anything, or another problem.

You said the fan works while +12 is applied to it, so I am going to say it is most likely that the thermostat is the problem. Connecting the red and white wires might start the furnace, and prove the thermostat is not working.

Fred.

Moved from Forum Technical Support

Did you turn the thermostat off and then back on? Not just sliding the temp adjustment down....but switching it off and then back on. Typically they will try to ignite 3 times and then shut down. Have to turn off and on to reset. Propane would have nothing to do with the furnace not even coming on again.

The 'timed delay relay' is part of your ignition control board.

Some models it is a stand alone relay......power from ON/OFF switch/CB went to the relay and then to blower motor AFTER power come from T-stat that energized a coil which when heated made up path in relay for power to blower motor.

You have power to board and power from T-stat....blower runs when you jumper power.

Bad ignition control board OR bad connections/ground on board.

Replacement board......Dinosaur Board LINK

Atwood 8500 Series Manual (Limited but has wiring & part numbers) LINK

Atwood 79/80, 85 & 89 Series Manual....more info with troubleshooting LINK