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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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My 3 amp fuse in control board keeps blowing, just today so

Customer Question

my 3 amp fuse in control board keeps blowing
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: just today so i replaced the thermostat and the fuse things were working for about ten minutes then the 3 amp fuse blew again
JA: Just to clarify, do you think this is a larger HVAC problem, or something specific to the thermostat?
Customer: im not sure it keeps blowing the one the control board where the furnace is located
JA: Do you plan on doing the work yourself?
Customer: yes
JA: Anything else we should know to help you best?
Customer: i replaced the capacitor in the out side unit about a year ago
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: 1 year ago.
Category: HVAC
Expert:  WCohn replied 1 year ago.

Hello, my name is ***** ***** I look forward to helping you! What model number are we working on?

Customer: replied 1 year ago.
bryant plus 80
Expert:  WCohn replied 1 year ago.

And the 3 amp fuse blows in the indoor unit?

Customer: replied 1 year ago.
in the control board in the indoor unit
Expert:  WCohn replied 1 year ago.

If you replace the fuse and check voltage while someone else turns it on I'd like to know what voltage you are getting out of the fuse terminals.

Customer: replied 1 year ago.
on the seconndary side of the control voltageb transformer on sec 1 and sec 3 where they terminate in the board im reading 28 vac
Customer: replied 1 year ago.
sec 2 not 3
Customer: replied 1 year ago.
what are you reading the fuse terminals to
Expert:  WCohn replied 1 year ago.


Expert:  WCohn replied 1 year ago.

28 volts is close enough to the 24 it should be. What started this problem? Did you replace the thermostat?

Customer: replied 1 year ago.
we cant talk im deaf this morning the old thermostat was junk fuse blown so i replaced the fuse with old thermostat still in place and fuse blew again so i took old thermostat out replaced fuse and it was ok so i put a new thermostat in and the system worked great for fifteen minutes and then the fuse blew again
Expert:  WCohn replied 1 year ago.

Think this is over my head I'm going to opt out so someone else can answer. Do not reply until another expert contacts you, if you do it will make it so your question is not visible.

Expert:  Brian HVAC Guy replied 1 year ago.

Hi I'm Brian and I'm here to help!

I've read through the entire conversation and am ready to pick this up with you if you wish. If the new thermostat is in the Off position or mode and the thermostat fan switch is in the Auto position or mode, does the fuse still blow when you apply power to the furnace? If so, at what point and what thermostat setting does the fuse blow?