Pressure Switch, Comb Air Blower Problem?

[jtreed2000]

I figured out tonight that my my Lennox G24M heater works if I pinch the tube going to the pressure switch after the flame ignites. (The tube goes from the combustion air blower to the pressure switch.) The C.A.B. is the first thing running I think(?) when the unit senses a need for heat. Here is what happens when I don't pinch the tube...

Without pinching this tube, the unit fires up the gas and it runs for 5 to 30 seconds or so, then shuts off, in cycles. It does this for about 2.5 minutes then shuts off for about 5 minutes with LED 1 - off, LED 2 - slow flash, The panel says "Pressure Switch Watchgard: pressure switch open during operation or condensation drain blocked."

Everything seems ok if I pinch this tube, except the CAB and flue get very hot. (Blocked flue? Bad CAB?) I don't know if that's normal. I believe the heat exchanger is still under warranty for another 7 years. It looks like the pressure switch is easy to replace if that's the case.

Here is an online link to the G24M pdf file: http://www.ultimatehvac.com/LinkedDocs/Lennox/9723b.pdf

The trouble code is listed on page 32, 33, Problem #3. I greatly appreciate the help.

[wallynut]

Please do not play around with your gas furnace, could be very dangerous,carbon monoxide poison or explosion.
That vacume switch is doing exactly what it should do,
let you know there is a problem and call Professional.

[curry]

Sounds like you are a busy little beaver.

Knowing part names does nota service tech make, therefor I say you shold call a pro.

The questions you ask show you know just enough to be dangerous to yourelf.

Get it done right.

[Mr Bill]

Probably got a loose hose at the inducer or at the pressure switch and by pinching it it's holding the pressure switch in make sure you have a tight connection at both points.

[Jultzya]

Welcome to HVAC TALK. However this site has rules against giving out technical advice to DIY'ers. I have attached a link below for your convenience.

Here's something to think about though...

When was the last time you had that unit cleaned and inspected?

Now you have a problem with the unit. Fuel costs are skyrocketing.

So why not call in a professional to repair the unit? While they are there they can clean and inspect your unit to insure a safe living environment for you and your loved ones. Not to mention, having an efficient running system could save you more than the cost of the service.

What's your safety worth? I'm guessing more than the repair bill.

Thanks for your understanding.

(we can't help DIY, due to site rules )

[jtreed2000]

I already called someone but it will be nearly a week before they arrive. I don't want to be overcharged, freeze in the meantime, and be told I need anything more than what's broken later. Before I did any reading I would have been more ignorant about this unit than before, so at least now I have some knowledge of the parts and operation now. It's $65 just for someone to come to my door btw. I agree that you cannot put a price on safety, but I didn't leave the unit in a "test" condition. I've been around electricity/gas long enough to know what's stupid and what isn't. The flame was already going when I held this tube, so I knew not much else would happen. The only thin I can imagine happening in that situation is the CAB or flue or heat exchanger gets too hot and catches fire ...eventually. That's unlikely to happen in only another 5 seconds or so. It's not running now and I turned off the gas to it before I posted this. I guess you guys must obey the site rules, but maybe it is just a loose hose or something simple. I wouldn't have to freeze my a$$ off for another week until someone arrives.