Goodman GMP075-3 Problem


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Old 01-09-09, 11:27 PM
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Goodman GMP075-3 Problem

The furnace just doesn't want to ignite. The small fans on the unit turns on then after a few minutes it just shuts off. The red l.e.d light is a steady red which is working normal per the back of the trouble shooting label on back of the cover.

I set the temperature on the lowest setting then turned up the temp and once it is over the room temp it kicks on, but the igniter does not turn red and there is no gas blowing.

What's the problem, really need help.
 
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Old 01-09-09, 11:49 PM
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What have you checked?

I'm assuming that you've checked to make sure that you have power from the transformer? I'm assuming so, since you have the LED, but check the voltage. You say it kicks on, but the igniter does not turn red. What kicks on, the thermostat? Is the signal getting from the thermostat back to the furnace? The igniter isn't getting red, is it getting power? If transformer is putting out 24VAC, and the tstat signal is making it back to the furnace, and the igniter is getting power, then it may just be a bad igniter, but you need to check everyting else first.
 
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Old 01-10-09, 12:26 AM
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Yes, the first thing I'd look at is the ignitor. Check for a visible crack, often surrounded by a whitish powder. Or check the resistance --- it's no good if the resistance is infinite.

If the ignitor is good, check both side of the pressure switch for 24 VAC after the inducer motor turns on.
 
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Old 01-10-09, 11:56 AM
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If you have access to a test meter, set the scale for 125 volts AC. Disconnect the ignitor at it's connector and rig the meter to the furnace side. Start the furnace. After the inducer motor runs awhile, the meter should suddenly jump from zero to 120-125 volts. If it does, the ignitor is bad. Just another way to test other than a resistance test.
 
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Old 01-12-09, 06:08 PM
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checked the resistance

I borrowed a volt meter and disconnected at the igniter. The igniter has resistance as well as the wires that connect to it from the blower motor.

When I turned it on the voltage stayed about 10-12 volts. I removed the service panel and noticed the LED light now blinking 3 times. The service panel says this is due to a pressure switch failure to close and to check the venter pressure switch vent blockage.

I am not sure what this means since I have not found a answer yet online. Thanks for the many replies, it has been helpful.
 
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Old 01-12-09, 06:30 PM
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The blinking light is now signaling that the pressure witch isn;t closing, and for that reason the furnace doesn't provide voltage for the hot surface ignitor.

Based on your finding resistance through the ignitor, it's probably OK.

Look for the rubber tubing leading from the pressure switch to a barb on the housing near the inducer motor. There is a barbed fitting there that is famous for accumulating corrosion which restricts the pressure measurement and shuts off the furnace.

Shut off the furnace. Take the rubber hose off the barb. Use a small diameter drill bit and run it down into the fitting and move it around to knock any corrosion loose. You need quite a small drill to get all the way down to the inside of the housing. (just do this by hand, no drill needed).

Reconnect everything and try it again.
 
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Old 01-12-09, 07:14 PM
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That did the trick

I used the drill and poked it through the inducer blower, then was able to hit the fan which was clogged as you said. Now it works like a charm.


Good advise Seattle Pioneer
 
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Old 01-12-09, 09:01 PM
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A tip---

Leave the drill bit in the crook above the inducer motor housing. It will be easy to find the next time you need to do this maintenance.

Further note ---

If you do this once/year just before the heating season starts, you probably wont suffer another outage due to that problem.
 
 

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