Goodman Gas Furnace Cuts Off Switching to LO Stage

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Goodman Gas Furnace Cuts Off Switching to LO Stage

Postby bushbag1 » Thu Jan 28, 2016 2:54 pm

Goodman 2-Stage GMV951155DXA starts on HI Stage and runs fine until called to go to LO stage. At this point the fan slows and within a minute the flame goes out and fan stops and error message "E1" is displayed (pressure or pressure switch problem). It then tries to restart three times, with igniter heating up but gas does not flow. Unit cuts off, and error message "E3" is display (meaning lockout after three unsuccessful restart attempts). Both pressure switches have just been replaced and the problem still occurs. I found Goodman Service Bulletin SF-043 online which says "E1" error can be displayed improperly on some units and lead to false diagnosis. Note that after the unit sits idle for 30 minutes or so, or if I flip the disconnect off and on, it will often restart successfully. If cold enough then it may start on HI and problem will repeat itself when moving to LO, but if it STARTS on LO then it will run successfully on LO, so I know its not just a problem with LO speed, just a problem with switching between HI and LO.
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- Goodman Gas Furnace Cuts Off Switching to LO Stage

Postby Freon » Fri Jan 29, 2016 11:53 am

First, check all electrical connections especially grounds.
Then I would TEMPORARILY jumper the pressure safety switch to verify the E1 error is accurate. Check the date of the service bulletin and if it applies to the date of your furnace's manufacture.The switch may not be the problem. It is usually the draft inducer fan that isn't developing enough air flow to activate the pressure switch. Or the pressure hosing can be clogged. By jumping the pressure switch you can see if the E1 error is accurate (the furnace transitions perfectly HI to LO) or if there is a problem elsewhere.

One strange aspect of the restart attempts is the fact the ignitor glows. Usually if there is not sufficient draft pressure from the draft inducer, the ignitor will not be energized. This fact points in the direction of a flaky control board.

But first let's rule in or out the draft inducer system.
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