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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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3 amp fuse keeps burning on the air conditioning fan circuit

Customer Question

3 amp fuse keeps burning on the air conditioning fan circuit board
JA: Sometimes HVAC issues that that you think will be really complicated end up being easy to fix. The HVAC Technician I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so we can help you best.
Customer: When I replaced the fuse and switched the fan from auto to on on the thermostat the fuse blew.
JA: Is there anything else the HVAC Technician should be aware of?
Customer: no...new circuit board............same problem as the old one. it doesn't do it all the time though
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the HVAC Technician about your situation and then connect you two.
Submitted: 9 months ago.
Category: HVAC
Expert:  airheatman replied 9 months ago.

If fuse is blowing this indicates dead short somewhere.Locating short can be time consuming and may take a few fuses to determine where it is. The following are most likely.

1.Bad thermostat

2.Skinned or chewed wire between thermostat and units

3.Bad contactors in outdoor unit

4.Skinned or naked wire in indoor or outdoor unit

5.Bad control board

First step is to get several fuses. Then start by disconnecting wires at thermostat and see if fuse still blows.Next disconnect thermostat wires at control board and see if fuse still blows.WE have to determine what in the circuit is shorted.

Customer: replied 9 months ago.
I have ordered another thermostat. thanks
Expert:  airheatman replied 9 months ago.

If that does not solve your problem let me know and I will be happy to guide you in locating the short.

If you have further questions, please let me know.

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