Furnace won't even attempt to ignite - Single mom needs help


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Old 04-28-09, 07:51 AM
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Furnace won't even attempt to ignite - Single mom needs help

Hi! Hoping someone can save a single mom a service call. Had a guy out a month ago to clean my gas furnace and flame sensor - I cleaned the flame sensor myself but used steel wool and was told next time to use fine sand paper cause the steel wool didn't do a good enough job. Anyway, got a little bit of water in my crawl space last night but don't think it got near the furnace, which is on a slab. Powered the furnace off and on. The power and ok light come on but the flame light does not. The fan kicks on but the unit does not even attempt to ignite (no clicking). There are no flashing lights/error messages. The diagnositc flow chart says something about a vent but I can't locate it on the chart. Am I gonna have to right a repairman a check? Please help me....
 
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Old 04-28-09, 08:27 AM
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Is your powervent fanmotor coming on? That starts up first before anything, and it is by that device that all other furnace functions are then allowed to progress. Does that run?

Even if it does runs, you must make sure nothing is blocking the venting in the pipe outside, like nest or if you have 2 pvc vent lines, one is for intake and there may be a leave stuck up against it if screened and maybe flew in pipe if unscreened.

If nothing applies so far, then you need a cheap voltmeter you can buy anywhere for cheap and test to see if you have incoming and outgoing 24 volt ac current from the vacuum diaphram looking device(called the pressure switch) that has 2 or 3 electrical wires and a 1/4 inch supple rubber tube connected to it.

If you are incapable of such a test, ask a friend or neighbor if they have experience in this, if you are desperate and can't afford say a furnace man. We then can instruct you or them how to do the meter test and what may be wrong with the furnace.
 
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Old 04-28-09, 10:09 AM
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Update - pressure switch thingy (hopefully resolution)

I saw a lot of posts about the pressure switch so I went back into my wet gravel crawl space (haven't gotten moisture in there in ten years so it figures), and started playing with and doing the suck/blow thing with the pressure switch (not easy when your furnace is on its side). Also, when I went back down I saw I was getting the double flash which meant "open pressure switch" (guess I wasn't patient enough the first three trips down there)

Anyhow, after much sucking and blowing and taking everything apart to see how it all works and a massive headache, I seemed to loosen up the switch enough to get the furnace to work. A side note though, the pressure from the fan connected to the switch seems very low - is it supposed to be very subtle like that?

I am going to order and install a new switch in the meantime. There seems to be a lot of problems with it with the Rheem Criterion II. I am also going to get that voltmeter you sugggested.

Any other suggestions? I'll update in a little bit if furnace acts up again or not but it just kicked on for the second time - yea!!!!. Thanks you a million times over!!!! Everyone else is posting gardening stuff and I have a furnace problem - go figure.
 
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Old 04-28-09, 04:03 PM
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Yes. It is very little suction getting to the pressure switch. It may be only .9 "water column" (which means you can even about half thatfigure for what the psi is.

But the pressure switch is calibrated in design to recognize that miniscule pressure. Any blockage in the tubing, the nipple where the tubing plugs into especially the fan housing itself - and, if there is a backup of furnace condensate water in the secondary heat exchanger because it can't drain out through a clogged hose or trap, will disrupt that vacuum enough to make the pressure switch not 'close'(you need to have it electrically close to allow the furnace to continue to run). That is why they have that switch. It is a safety device.

I would not just replace the switch. I would test the switch to see if it is "open"(electrically has contacts that are not completing the circuit) during when the inducer fan runs, and then clean out the stuff I suggested. And then see how it behaves?
 
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Old 04-28-09, 04:07 PM
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Originally Posted by judi View Post
Everyone else is posting gardening stuff and I have a furnace problem - go figure.
Tell me about it. Up where I live, we have gone from sun/88 out recently, to below freezing and frost, in one day. Nothing unusual for us here in Wisconsin.
 
 

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