So my furnace stopped working some time ago. I meant to troubleshoot it already but so busy with home renovations and other things going on, and I just keep forgetting about it. But now its been over a year since a fill and they are going to be charging me rental fees. I am debating ditching the bulk tank, but want to make sure the furnace is working first while I still have propane to test it. I figured it was igniter, after doing some research they seem to be common to fail, but I finally went down there and opened the thing up and the ignitor is glowing bright. Everything obvious is working, exhaust fan comes on, etc. How to test if there is actually propane going into the system? Should I be able to smell it out the exhaust if its not lighting? I assume I'm not getting propane, unless there is something wrong with the regulator on the tank then I guess it must be the gas valve in the furnace then, or something wrong with the power to it? There are 4 wires going in, the two green ones I assume ground, one or both the other should be 24v but not sure why there is two. I'll have to dig up a meter and see what happens. Any other advice?
Suppose someone turned the valve off on the tank and forgot since you've been so busy? I wonder if yooperdave has any ideas?
Thermocouples fail too, but if you aren't getting gas at all I would bet its the valve. Check that you have power to the valve. Propane has an odorant put in, so there should be a smell if you are getting gas.
If it is failing to fire, then it is the valve, but if it is failing to STAY LIT then it is the thermocouple. 9 out of 10 times it is the thermocouple.
Does this unit have a diagnostic flashing light on a circuit board? Sometimes there is a small round sight glass to look through to see it. The service panel cover would have the error codes listed if there was one. Check wiring connections, check flue if accessible to see if there is a hornet nest or some other obstruction that would cut draft. Sometimes high limit switches, draft sensors or flame roll out sensors can fail.
Oh I forgot to state exactly what it is doing sorry... it does not light off at all. Igniter appears to be working. I did not smell any propane in the exhaust but I wasnt sure how diffuse it would be by then. fishingpol - I didn't notice any lights or anything on control board but I'll go down and check again when I get the chance. And I'll double check the venting for obstruction, didn't know there could be a draft limit switch. wildwest - as far as I am aware there is no valve on the tank (500g) only valve I can find is where it goes into the furnace.
Man, there better be a valve on the tank! Don't know if this is a high efficiency unit or not? What type of gas line do you have hooked up to the furnace? Copper flare fittings? I can see black pipe going to the gas valve so I would think that there may be a union on the outside of the furnace cabinet (typically) that you would crack AFTER you shut off the gas valve by the furnace. Then, make sure the furnace is off and turn on the gas valve BRIEFLY/QUICKLY. If there is gas available, you will hear it and smell it. DO NOT leave the gas valve open long. If you do indeed have gas available, start checking why the gas control doesn't allow the furnace to fire. There are a number of safety's built into the trial for ignition sequence that will not allow the furnace to ignite if all conditions aren't satisfied. "If it is failing to fire, then it is the valve, but if it is failing to STAY LIT then it is the thermocouple." (from above post) This is not necessarily an accurate statement and may cause you to change out the gas control without solving the problem! Even something as simple as a plugged condensate drain line (this is one reason why need to know if its High Efficiency) will not allow the furnace to fire. Blocked intake or exhaust venting? Limit switches tripped? Plugged up secondary heat exchanger? Flame rollout limit tripped? Need more info! Like fishingpol mentioned....check for diagnostic lights flashing in short and long sequence (usually on bottom door of unit) and refer to the code on the inside door of the furnace. If you interrupt the power, this will re-set the flashing lights code sequence and will have to start all over again to try running it before they will show up. Hope you still have the owners manual?
Wow thanks for all the comments fellas! Ironically I had just fixed my ex's Rheem furnace, bad ignitor, same one mine takes but that is about the extent of my knowledge on fixing furnaces (well and replacing oil burner ignition transformers and wiring up thermostats). I should have zoomed out a bit in the one pic, would have answered some questions. I'll snap a couple more pics in a bit. Looking at the tank I see the shut off valve now. I suppose it'd have to have one of course, I feel dumb about that. Was pointing out the back towards the bushes, never noticed. But it's never been touched and wasn't closed. About 20% on the gauge. It's a Rheem 90 plus 120k btu forced air lp furnace circa 1990. There is no sight glass on the panel, and the control board is in another closed box with no sight glass, but opening it up I did see 3 led's on the board but no codes anywhere. The first two green ones light up as soon as I power up the furnace. And no I don't think I have the original manual. On the inside of the control box there was a troubleshooting guide, I'm on the 5th box down "main burner lights" -> no I pulled the top two wires to the valve and after the 34 second warmup it did go to 25vac across them. So whatever permissives this unit may have must be met. So I did as yooper suggested and loosened the union and after cracking open the valve there was pressure and smell. So looks like it is a bad gas valve, now onto trying to find replacement unless I am missing something. Oh and since I've never messed with gas pipe connections, is there suppose to be any sealing compound or anything on the union? When I disconnected it appeared to be something on the surface, unless it was just moisture and corrosion, just want to make sure I am not leaking propane afterwards. Thanks for all the help fellas!
no sealant just tight.....during the 34 second warm up tap the valve gently could be a stuck seat from sitting for so long
Make sure your condensate line is free and clear....there appears to be a lot of corrosion on the furnace cabinet where the condensate line empties into the tee and then the drain tube. This corrosion may indicate that the condensate trap is plugged. If so, furnace will not ignite. Be sure that the condensate trap itself is not plugged up also. May look like this. Check the knob position on top of the gas control to make sure that it is in the "on" position. May need a mirror to read it? Check to see if you have a reset-able flame roll out switch. In the burn box area-two wires lead into it and usually a red plastic plug that you can actually depress to reset in the center of the roll out safety. If this has been tripped, it probably means that your heat exchanger (primary or secondary) may be plugged up with corrosion, etc. May look like this. Clean your flame sensor with steel wool. Careful....don't touch hot surface ignitor...you already know that. May look like this-located in the flame path (obviously). Shut off power to the furnace for about a minute. This may remove the unit from lockout if it already hasn't been done. Check exhaust vent for obstruction. Maybe something made a nest in the unused pipe??? Intake looks OK, but go ahead and check that too making sure it is free and clear. Does the vent motor run on trial for ignition? Make sure it is operating. Sometimes, after non use, it sticks and you just may have to give the rotor a spin to free it. On yours, looks like you'll have to remove it from the housing.
If the igniter glows, there are no safeties tripped. Gas valve is not opening. If you have inlet gas pressure and 24volts to the valve, the valve is bad. Like mentioned above, tap the valve during the ignition period, it is possible for the valve to open and work correctly again; no telling for how long though. Edit: spelling
