Furnace out in cold ass Michigan

[lendaddy]

Amana propane furnace, maybe 7 years old "air command 95"

It was blowing cold air when I got home, so I assumed ignitor. Pulled the ignitor and it tested fine.

So I double checked the tank, also fine (20%).

Then I spoke with a tech and it was the over temp rollout switch and when I reset it she kicked on. He said to check the vent and I went outside it was blowing out fine.

So, I get back inside and she's blowing cold again......you guessed it, the overtemp switch popped again. So I reset it and watched it trip again after 5 min.

Everything looks ok, should I assume it's a bad switch and just jump it for tonight or what?

Is there a diagnostic I can do on the switch?

[Sonic dB]

Id be on my way to Meijer's to pick up a couple of space heaters cause its going to be a long night...

[Jim Richards]

It's B2's fault.

[rick-l]

I take it there is a fan and it is running?


edit; the fan that blows air across the heat exchanger

[lendaddy]

I'm pretty sure I have a cracked/rusted heat exchanger.........again. I bypassed the exchanger for now and am debating if I should do that for the night (carbon monoxide and all). I have to CO alarms in the living area....but.

[Jim Richards]

It sounds like the switch is bad. I'm not sure about the diagnostics since I'm not sure what part of the furnace the overtemp switch is monitoring. If it's the heated air coming out of the blower, maybe use an oven thermometer to measure air temp while measuring the voltage drop across the switch contacts (in circuit), or the resistance across the switch with the wires disconnect and jumped together. I would consider jumping overnight it if I was absolutely convinced the thermostat was functioning properly and the outlet air temperature wasn't unreasonably hot. If you do jump it, watch it for a while to gain some confidence that the thermostat is doing its job. Then replace the overtemperature switch tomorrow.

Disclaimer: Without actually seeing the furnace manual and schematics, I'm winging it and my advice may be sketchy. Still, I hope it (safely) helps you out.

[tdatk]

That sucks Len.
I'd be looking into this asap


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[Jim Richards]

Oh, heat exchanger issues, too? Any nice hotels / motels nearby?


edit: Oh wait, you guys worry about freezing breaking pipes, don't you? Sheet!

[lendaddy]

Yea I think the IIQ is the newer version but I'll check.

[lendaddy]

Wife wants to take the kids to Grandmas, hmmmmm.

[turbo6bar]

Can you check the temp at the rollout switch? Is your filter fresh?

If the temp is not 180- 200, then I think you are fine to jump it. Does the switch trigger immediately after the system lights or after a few minutes?

[lendaddy]

Originally posted by turbo6bar
Can you check the temp at the rollout switch? Is your filter fresh?

If the temp is not 180- 200, then I think you are fine to jump it. Does the switch trigger immediately after the system lights or after a few minutes?

I actually pulled the filter all together once to see if that changed anything and it did not.

It does not trigger immediately, it takes about five minutes.

[turbo6bar]

I'd make absolutely certain the temps don't get above 200, before jumping the terminals. Some temp switches trigger at lower temps, though. Proceed with caution.

[lendaddy]

Originally posted by turbo6bar
I'd make absolutely certain the temps don't get above 200, before jumping the terminals. Some temp switches trigger at lower temps, though. Proceed with caution.

I don't have a tempgauge

[Jim Richards]

I imagine the thermal element (resistive, bi-metalic, solder-pot, ???) within the switch has probably has failed.

[rick-l]

Originally posted by Jim Richards
I imagine a thermal element (resistive, bi-metalic, solder-pot) trips the switch, and probably has failed.

or the heat exchanger has a huge crack and shoots flames/hot gasses onto the switch

could be either one

I'd check for airflow first.

[turbo6bar]

Eck, you're no fun.

If you're going to jump it over, stay by the furnace and make sure the plenum doesn't get freaky hot. Without some rudimentary troubleshooting, I recommend you babysit the monster through the night. Better safe than sorry.
jurgen

[lendaddy]

FWIW I have the cover off and the flames do not lap at the switch or anything like that. When it first sarts up they do for an instant but that's it.

When the blower kicks on I can't say for sure that the flame moves or not (supposedly a clue that the exchnger is cracked).

[speeder]

Christ, I wish I knew more about furnaces and could help. I don't envy you guys this time of year, that cold is no joke (as much as we joke about it) and it can be seriously dangerous.

I almost froze to death one time in my life and to this day it is a big fear. probably one of the reasons I live here.

[turbo6bar]

At the very least, if you're gonna use the system for the night, babysit for at least 2 or 3 cycles.