Furnace won't lite pressure switch open code 2

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Old 09-22-20, 07:34 PM
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Furnace won't lite pressure switch open code 2

Nordyne kg6rc. Was working at the end of last winter. Now when I turn it on all that happens is the exhaust blower turns on. The red LED blinks twice (pressure switch open with inducer on). I removed pressure switch hose the combustion chamber(?) amd cleaned out the hole which used to clog up a few years ago. I also jumpered the wires to the pressure switch which gave me a steady on LED (relay shorted).

During the summer while the furnace was shut of the propane ran down to 10%. Could this have caused a problem with the gas supply (air in pipe, etc)? My water heater is working fine.

The igniter has continuity through it.
Exhaust blower is running fine (replaced last year).
No condensate build up.

Any ideas what might be wrong before the repair guy gets here?

EDIT: I just checked the continuity on the pressure switch (part #632444) and it reads (with both wires disconnected) "OL" (infinite resistance).

Is this my problem.
 
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Old 09-23-20, 05:10 AM
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You can have a clogged pressure switch, the tubing can be clogged, and the orifice in the blower housing can be blocked. Have you checked the entire pneumatic path to make sure it's clear. You can also disconnect the tube at the blower housing and blow/suck into the tub gently to see if the switch is reacting.
 
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Old 09-23-20, 10:19 AM
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That is correct. The pressure switch rests at open..... infinite resistance.
There is tiny hole at the draft inducer blower that needs to be cleaned. Not the fitting itself but the tiny hole at the bottom. You'll need a small straight pin or miniature drill bit.
 
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Old 09-23-20, 11:00 AM
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I will check the hole on the blower and the tubing and stuff in a while. In the meantime here is my progress. This morning I rechecked the switch with some new info I found. Press switch reads "OL" and then with furnace turned on it continues reading "OL". I have 27 volts on one wire to the switch and near zero volts on the other (.014 volt on something near there). I then bypassed the switch and the burner did lite. So it IS either a bad switch or a lack of pressure or vacuum to activate the switch.
Remember, the furnace worked when it was shut off in the spring. Is that a clue?
And also remember that I am not a technician, so if I am in dangerous territory let me know. But I am used to doing my own repairs on most things.
 
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Old 09-23-20, 11:27 AM
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I find no hole at the bottom of the inducer blower except for the one with the drain hose attached.
One pressure switch hose goes from the switch up to the regulator and the burner box and the other hose goes into the bottom left corner of the collector box. I disconnected the hose at the collector box and sucked or blew and the switch continuity registered on the meter.
I think that the issue IS the lack of pressure or suction reaching the switch.
How big is this hole I am looking for on the inducer?
Where that switch hose attaches to the collector box, I had to clean that hole out a couple of years ago and that was the problem.
Is the hole I'm looking for a fitting or just a hole with nothing attached to it?
 

Last edited by sofasurfer; 09-23-20 at 12:33 PM.
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Old 09-23-20, 01:57 PM
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You want a clear passage from the blower to the switch so it can sense the pressure. If you've verified that the hole, tubing and switch are not clogged it could be something else. Maybe gunk has gotten deep inside the switch causing it to need too much pressure to actuate. In that case replace the switch. Also make sure the exhaust/flue is clear and not blocked by a nest or other debris.
 
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Old 09-23-20, 02:27 PM
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We use a manometer which checks and monitors the vacuum on the pressure switch.
Without one it can be difficult to find where the problem is.

Make sure any of the smaller lines are completely clean and check the locations where they connect.

I can probably grab you a manual if you post the complete furnace model number.
It can be found inside on the sidewall on an ID tag near the burner.
 
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Old 09-23-20, 03:33 PM
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Thanks for all your help and advice. I have learn so much about my furnace and now I know I don.t have to be afraid of working on it.
I found that I gad a yellow jacket nest in my vent pipe. Hooked the shop vac to it and sucked it out.
However, now I have a sound of slurping water coming from the drain hose that is connected to the collector box (not the hose coming from the inducer blower). What is causing it and how to I correct it. There is no water in the drain hose.
 

Last edited by sofasurfer; 09-23-20 at 04:21 PM.
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