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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8263
Experience:  Furnace, A/C and heat pump specialist.
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Goodman GMSS960803BN. Red light flashes 3 times, "pressure

Customer Question

Goodman GMSS960803BN. Red light flashes 3 times, "pressure switch stuck open"
Submitted: 11 months ago.
Category: HVAC
Expert:  airheatman replied 11 months ago.

Does the small vent fan come on and stay running?

Customer: replied 11 months ago.
No
Expert:  airheatman replied 11 months ago.

OK that is why pressure switch is not closing.The small fan has to pull a vacuum on the switch. Do you have a lot meter for troubleshooting?

Customer: replied 11 months ago.
I have a multimeter, not sure what a lot meter is?
Expert:  airheatman replied 11 months ago.

We want to see if motor is getting 110 to 110v on call for heat.Check voltage for 115V at the induced draft motor terminals during the trial for ignition. If you have 115V and the motor does not run, replace the induced draft motor.If we do not have power to motor we will go a different route

Expert:  airheatman replied 11 months ago.

LOL Typo should say volt meter. Lets unplug wires at induced draft vet motor. Turn thermostat to call for heat and see if we get power between those two wires.

Expert:  airheatman replied 11 months ago.

Anywhere between 110 and 120 vac is acceptable.

Customer: replied 11 months ago.
Am I checking the terminals on the pressure switch?
Expert:  airheatman replied 11 months ago.

NO the wires going to the vent motor. There should be two wires going to vent motor.Disconnect them from motor and stick leads into the terminals you disconnected.

Customer: replied 11 months ago.
The only wires that I can see going to the vent motor don't have terminals, they're wired to the base of the motor.
Customer: replied 11 months ago.
I can send a picture
Expert:  airheatman replied 11 months ago.

That would be great.There has to be a removable connection so motor can be replaced

Expert:  airheatman replied 11 months ago.

Follow the white and black wires .There will be a plastic connector connecting the wires .Unplug that connector

Customer: replied 11 months ago.
wires at base of motor
Expert:  airheatman replied 11 months ago.

Follow them to the plastic connector and unplug connector.See link above

Customer: replied 11 months ago.
I see what you mean, sorry they're tucked behind a bunch of other things and I couldn't see the connectors. Thanks.
Expert:  airheatman replied 11 months ago.

No problem, Unplug and stick one lead into each of the female sides of pug, call for heat,make sure door panel is in place or door switch held in and see if board is sending 110 to 120v to that plug.

Customer: replied 11 months ago.
Thermostat calling for heat, switch held in, no reading with the female terminal
Customer: replied 11 months ago.
female terminals
Expert:  airheatman replied 11 months ago.

OK lets do this.Follow those wires all the way back to control board.Unplug the connector on board where induced draft motor and hot surface igniter plug onto board, Check between the terminal where black connects and the white neutral to see if we get 120v

Customer: replied 11 months ago.
Trying to figure out which white neutral
Customer: replied 11 months ago.
Looks like the third one based on the diagram?
Expert:  airheatman replied 11 months ago.

All neutrals connect together so any one is really fine

Customer: replied 11 months ago.
female terminals?
Expert:  airheatman replied 11 months ago.

Terminals on board this time

Customer: replied 11 months ago.
Thanks
Expert:  airheatman replied 11 months ago.

No problem

Customer: replied 11 months ago.
No reading
Expert:  airheatman replied 11 months ago.

OK one more test just to make sure thermostat is not issue, Go ahead and reconnect everything we have disconnected Then on control board where thermostat wires connect. Use a wire, a pair of needle nose or a paper clip and touch the R to W terminal and see if inducer motor come son (Door switch in of course)http://i.imgur.com/JprQdYv.png

Customer: replied 11 months ago.
Used a paperclip and pushed switch in, nothing different (red light still blinks)
Expert:  airheatman replied 11 months ago.

OK from all we have checked it appears your control board is failing and will need to be replaced .Immediately upon call for heat the board should send 120 volts out to the inducer unless we have an open limit in which case we would get a 4 flash code.

If you have further questions, please let me know.

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Customer: replied 11 months ago.
The furnace was installed in November, any reason why it would fail so soon?
Expert:  airheatman replied 11 months ago.

Could have taken a power surge as these boards are susceptible to spikes. Good news is it should be a warranty issue.Parts as well as labor if installed by a licensed contractor.