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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5489
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a Coleman Model #dgaa090btda I replaced combustion

Customer Question

I have a Coleman Model #dgaa090btda
I replaced combustion switch. Had a indicator light flashing two times. This says combustion air switch stuck closed.
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.
All work to be done by licensed professional. WE KEEP GOING UNTIL YOU HAVE THE INFORMATION YOU NEED, I come and go. This is step ONE.

Hello, welcome to Just Answer!

Click here for the manual on the unit.
Please confirm this is it.

See page 13, locate the 'manual reset limit switch' on the left side of the diagram. you can find it on the unit by following the wire from the gas valve... see diagram for which of the two wires.

Press the reset button. Tell me how that works, we can proceed from there.


Please hold rating my service to you until we get this fixed or come to a viable conclusion.

Thank you !
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5489
Experience: Retired HVAC/ Electrical & Boiler contractor. Industrial
Phil and 4 other HVAC Specialists are ready to help you
Customer: replied 1 year ago.

I reset. Still two lights flashing after 45 seconds.

Expert:  Phil replied 1 year ago.
Hello again, if the error code says the air pressure switch is stuck closed, and you replaced the switch, and it still issues an error code that the switch is stuck closed, then the control card or wiring to the control card is defective... it is giving you a bogus read.

That statement is in the range of 90% correct...but not 100% correct. We can do a few tests. remove one of the wires from the pressure switch and see if you still get that error code read.

We can go from there.

.
Customer: replied 1 year ago.

Yes still same code I removed 1 and tested and then the other. Reconnecting previous.

Expert:  Phil replied 1 year ago.
Thanks. the error code should have changed when you disconnected the pressure switch wire if the control card was working right... if you got the same code with the wire disconnected, the control card is bad for sure.

If you only go the same error code after you replaced the wire on the new pressure switch, then the chances are 90%+ that the control card is bad.

There is one anomaly, the wiring diagram provided for the model series, and that I have attached, shows no control card and lists no diagnostic codes. We need to compare the wiring diagrams in that for your model number against the instruction manual you have on site that defines the error codes.

Still however, these tests below are still relevant.

Please compare what your manual shows compared to the manual that coleman provides on line here.


Next test. Use a multi meter set on ohms across the pressure switch with both wires removed before the inducer fan starts... it should read open contacts, same as with the test probes held in the air. And it should read closed contacts after the inducer fan starts.

If it reads that way, the pressure switch is good and the control card is issuing a bogus error code... thats a primary symptom of a bad control card.

We can go from there.

.
Customer: replied 1 year ago.

I was finally able to get multi meter and tested pressure switch. Checked out.


I also turned on furnace and blew switch open. The furnace fired up, but as soon as I put hose back Furnace shut off.


Is there any other test for circuit board being faulty.


I would hate to send for part and find it was not the problem.


they run about $125


 

Customer: replied 1 year ago.
Relist: Other.
dont want to wait for phil
Expert:  jj replied 1 year ago.

I agree with Phil. Replace the board. I read all of his troubleshooting and he led you down the right path. Please remember that an expert is not always right but if they know more than you you should take the advice. Also remember to rate his help.

Expert:  jj replied 1 year ago.
just a follow -up to see if replacing the board helped
Customer: replied 1 year ago.

Yes it did. I also cleaned combustion motor and furnace is working perfectly.


I just finished installing this afternoon Great timing.


Thank you for your help.

Expert:  jj replied 1 year ago.

You are welcome and I will pass the word along to Phil. One more thing, would you please finish the process by rating my help.

I look forward to helping in the future if need be.

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