I have Goodman gmn080-4 furnace. It won't light the ignitor, and has 3 flashing red lights which I was told was the vacuum switch, which I tested by blowing on it to verify it opens and closes.

Here is the sequence..

1. start the furnace..
2. Transducer kicks on and runs for about 10 minutes.
3. Furnace doesn't kick.

I've replaced the hot service ignitor, element, and vacuum switch..

Please help!!

To find out exactly what the blinks mean look on the back of the furnace blower for a legend.

Check the rubber hoses connecting vac switch to the unit. Blow on them to check switch operation and check for cracks or other air leaks. Did you use a meter to verify the vac switch works or just listen to the clicking? Also make sure the power venter is producing air (check for pressure outside and make sure the pipes are clear of debris etc.)

If I were running through a test of the furnace, first I would look at the hot surfice ignitor, I would look for a crack in the lighter, if you can not see it very well take it off so that you can see it good enough to see if it has a crack. (Warning do not touch the material with your fingers, your body oil will make them burn out.)

If you do not see a crack then I would use my volt meter to test for voltage going to the pilot. Unplug the pilot, insert your probes into the holes that the pilot wire came out off Turn the furnace on and after the vent assist motor comes 0on watch the meter, maake sure that you have 120 volts reading on the meter. If you do have voltage it means the pilot is bad. If you don't have voltage it is time to look for other things.

I've replaced the hot surface ignitor. No voltage going to it.

It seems you have replaced or checked most of the parts in the unit. I hate to say this but I would be checking or replacing the circuit board. But this all does not make any sense since it was flashing 3 which you stated was the vac switch. By pass or jumper out the vac switch and test to see if it fires. The board is expensive so I am just trying to make sure before replacing.

How do I jumper out the switch? Does it help that my ac kicks on as far as the board is concerned?

Thanks for all of your help!

Jump the switch wires for testing purposes only. Do not operate unit for any longer than the test with the wires jumped. The vac switch is a safety device.On the A/C side all it does is direct power to the outside contactor and activate the blower relay.

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Originally Posted by raydizzle

I have Goodman gmn080-4 furnace. It won't light the ignitor, and has 3 flashing red lights which I was told was the vacuum switch, which I tested by blowing on it to verify it opens and closes.

Here is the sequence..

1. start the furnace..
2. Transducer kicks on and runs for about 10 minutes.
3. Furnace doesn't kick.

I've replaced the hot service ignitor, element, and vacuum switch..

Please help!!!

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I had the same issue and bypassed preasuure switch and jumped it. Fired right up. Needed a new preasure switch which you can get from AllPart on line for 26. Orso. Cheap.