York Diamond 90 - works when hose disconnected

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Old 12-24-11, 07:08 AM
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York Diamond 90 - works when hose disconnected

Hello

I have had a York Diamond 90 furnace for 11 years and had no issues until 3 weeks ago. I have this weird situation where the surface ignitor would not come on unless I disconnect the end of the rubber hose from the burner box. There are two rubber hoses (one to the combustion blower and one to the burner box) connected to the pressure switch. If I take the end of the rubber hose that connects into the burner box, everything works normally. I called in an HVAC tech who spent hours troubleshooting, cleaning intakes, exhaust, blowing through hoses, disassembling pieces, found no blockage that i know of, even mentioned that he pretty much did a complete tuneup of the furnace, and could not find anything. He suggested to replace the pressure switch which I did myself with a new one but no luck.

Any advice would be greatly appreciated.

Thanks
 
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Old 12-24-11, 08:22 AM
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ensure the exhaust pipe has no sags in it and that the pipe slopes at least 1/4" per foot from the termination point to the furnace. Also look for the drain trap and make sure that it is clean.
 
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Old 12-26-11, 05:24 PM
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Hi hvactechfw

Thanks for the response

I checked the exhaust pipe (this is the pvc pipe that is connected to the combustion blower and goes from the furnace to the outside, correct?) and did not see any sags. The sloping appears to be ok as it has always been like that. I checked the drain trap and found dead insects and cleaned it thoroughly. I also checked the black hoses connected to the drain trap and pvc piping going out. Still the same result.

With the plastic (it is actually plastic not rubber) hose connected to the burner box, the coil (or surface ignitor?) in the burner does not glow or turn orange, and no clicking sound. Nothing happens. The motor starts but the air blower does not start. It is weird that if this hose is not connected to the burner box, everything works. Would the pressure switch even work if it's hose is not connected to the burner box?

I am at a loss, not knowing what else to check . I thought it was the pressure switch but I did get a new one but still did not matter. Do you think the blower unit or motor have something to do with this? That is one thing I know we have not taken apart and open up.
 
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Old 12-26-11, 05:51 PM
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The pressure switch is a safety device that proves proper venting. You are going to need to call in a pro that has a manometer and can check the heat exchanger and venting system. There is a chance there is a heat exchanger issue. (MAJOR SAFETY ISSUE)
 
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Old 12-28-11, 08:56 PM
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I went ahead and contacted another service company and they took some time but they fixed it. Woo hoo!!! The problem was in the blower. Apparently the disc or wheel inside the blower (draft inducer) was too close to the opening where the hose from pressure switch is connected to (rubber hose connects from pressure switch to combustion blower) and that must have restricted the air flow. One of the more experienced tech (i got two to diagnose, a plus) used a pointer to nudge the wheel away from the combustion blower opening, turn the motor manually by a little, and repeated this 3 times. Plugged ALL the hoses in place and everything back to normal.

I am glad I got the best techs out there who did not give up. I am happy because I do not have to pay thousands of dollars for a new furnace.

Thanks
 
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