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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Working on a Ducane central furnace, mpga05083a. It blows

Customer Question

Customer: Working on a Ducane central furnace, mpga05083a. It blows the fuse on the control board when I plug in the 6 wire harness between the control board and the smart gas valve. I've replaced both the valve and the control board and nothing changes. I checked the wires totally and there are no bare spots. if I cut the red wire (data) the problem goes away but of course when I hook it back up it blows the fuse again.
JA: Thanks. Can you give me any more details about your issue?
Customer: furnace won't run because it blows the fuse. details are above
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Submitted: 1 year ago.
Category: HVAC
Expert:  BillyHvac replied 1 year ago.

hello,

have you unhooked the pressure switch and limits one at a time ?

we want to eliminate one switch at a time that runs from the harness

Customer: replied 1 year ago.
all the safeties have been unhooked, I had the same idea. hot surface igniter and sensor also unhooked.
Customer: replied 1 year ago.
I was hoping you had heard of some similar situations with lennox or Ducane units
Expert:  BillyHvac replied 1 year ago.

No, this is a odd situation. Since it is a fuse on board it will only be a low voltage issue. Is the thermostat wire attached to board when fuse blows?

Customer: replied 1 year ago.
no
Customer: replied 1 year ago.
I'm head chiller tech for a school district but sometimes the small stuff can throw me, I have disconnected everything but those two plugs and 24 v power
Expert:  BillyHvac replied 1 year ago.

this is a strange one...let me open this up to the others..

Customer: replied 1 year ago.
Thanks

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