Gas furnace / thermostat problems

onceling

Short version: guy cleaned ducting/furnace maintenance during summer and it worked when he tested it before leaving but now furnace won't start for heating.

I think the first thing to check is that the thermostat is even sending a signal to the furnace but I don't know what to look for? I took off the front plate and then realised what am I doing I don't know what to look for. The little mercury bubble thing still moves around and the coil is ... well it's still there but I'm aware they get bent, not even sure how to tell if its bent?

That said, I'm not hearing a click or anything like usual from the thermostat so I'm hoping its the problem. Any ideas how to test a thermostat? Even on the highest setting it doesn't start, but what to do to fix it?

It's a gas furnace for only heat, and I've got the instructions out and the only switch is on and the gas line is open but it doesn't even show me a way to start the furnace on its own. Feeling retarded. If I could figure out how to start the furnace on its own I could definitely know at least what is to blame.

There's only 2 switches (on the furnace), one is a lever which I have tried in both directions but is currently set correctly to on. Then there is the power button on the door, the override, and it doesn't do much but is operating correctly if it matters.

phekno

***EDIT DISCLAIMER: BE VERY CAREFUL!!! 24VAC ISN'T A LOT, BUT BE CAREFUL ANYWAY!

Is it possible that the guy cleaning it turned it off at your breaker panel? I would check there.

Otherwise, you could check to see if there is voltage on one of the wires coming to or from the stat. I can't remember which ones RC/C (names, not colors) should be like 24VAC (across those two terminals). I think that's the power supply for the stat. Then there should be another set of wires coming off the stat to call for heat. Maybe they're OB and C. If the stat is calling for heat (or should be calling for heat) there would also be 24VAC there.

I test thermostats (kinda), but not the one you're talking about (I assume you're talking about a Honeywell "button" stat?)

***EDIT DISCLAIMER: BE VERY CAREFUL!!! 24VAC ISN'T A LOT, BUT BE CAREFUL ANYWAY!

onceling

I did check the breaker panel last night, all looks good in there.

Thanks for the advice on checking the thermostat, going to follow your instructions later today.

And yeah, its one of these:





The little white line is showing roughly the right temperature (am in Canada) but when the lever is moved even all the way to the right past it, the furnace doesn't respond.

Midshipman

Most likely your pilot light is out in the furnace. If you can post a picture of the furnace valves I might be able to walk you through doing that. Otherwise google for pilot light instructions for your furnace type.

P.S. with general pilot light instructional video.

http://www.youtube.com/watch?v=qBUP3yrwliQ&feature=related

onceling

It has an igniter (which the guy said he cleaned but the dude obviously did something suspicious to my system so who knows about that??) rather than a pilot light. We've had to relight the water tank a couple times so we hoped it was that too but apparently not.

EDIT: I can still post a picture of the furnace when I get home later tonight.

Midshipman

It's worth a shot. I haven't dealt with an ignitor furnace before but I'd still suspect that the problem is more likely to be at the furnace end than the thermostat end. Thermostats are fairly robust.