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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8769
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a 5a fuse in a trane xr80 that keeps blowing, the

This answer was rated:

I have a 5a fuse in a trane xr80 that keeps blowing, the board is a white-rogers
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: started about a month ago, I found the switch on the side of the furnace/blower had a bad ground, i properly grounded the wire and it worked for about 2 weeks, then the issue started again. I replaced the switch and board but still have the issue
JA: Did you check the furnace's filters?
Customer: filter is new
JA: Do you plan on doing the work yourself?
Customer: trying to, the last AC guy charged me $500 for exactly nothing the last time I had an issue
JA: Anything else we should know to help you best?
Customer: sure, the contactor was also replaced when the initial issue came up(friend in the business did that). also checked/tested the 2 wires that run from the board to the A/C(red and white i think), spliced in partial wiring to see if it was justn= cut somewhere but no luck

Greetings, unplug one of the molex connectors to the board at a time, until the fuse ceases to blow, it will be that last circuit attached to the board that has the short in it.

If you unplug all of the connections to the board and the fuse still blows, then I will coach you on how to replace the board as long as you rate my input so far positively,


Important note about RATING my work:

I am a retired mechanical engineer and HVAC/electrical/ refrigeration and boiler contractor... with 56 years in this business. The last 20 of those years consulting for major firms nationally..


All I ask is please respect ne and my input by selecting the***RATING LINK***at the top of your page, that is the only way I am credited through the site.Rating does not affect your charges nor ability to refund if not satisfied.


If you need to be coached through a full diagnosis/repair,and wiring etc. for up to two days, and wish to be trained to use test instruments...... that goes well beyond' Just a simple Answer' of course, and goes beyond what most other experts here offer.....rate my simple answer so far positively.. and I will deliver that training and coaching to you All on the same dime so to speak.


Lacking a positive rating I can spend days helping a person at my own expense and loose my shirt,shorts and socks on the deal.


Attach a close up photo of the wiring diagram glued to the inside of the blower access door and I will mark it up with troubleshooting instructions then follow up with step by step training and coaching until you have a solution.


Photo must be exceedingly well focused. Use the 'add files' link next to your send button to get the photo to me.


Phone call offers:

If you wish to accept the companies $25 phone call offer,if indeed they send you one, this will go a *lot faster, but it IS 100% optional... or we can continue here in this dialog box at no additional charge.

Phil and other HVAC Specialists are ready to help you
Customer: replied 2 months ago.
this board has a 12 pin and 4 pin connector slot, does it matter which one I pull first?
Customer: replied 2 months ago.
little more info, when the a/c is switched to off the blower works and the fuse does not blow, when I switch the a/c on is the only time it blows, should i still pull the connectors.

try it both ways, then take a close up, exceedingly well focused photo of the units wiring diagram glued to the inside of the blower access door and I will look those circuits over for you, and prescribe more tests

It sounds like the thermostat wire that runs to the outside unit is rubbing on a bare metal opening in the unit and has shorted out, that is very common. look that entire area over very closely.

We can go from here without a time limit in the morning

Customer: replied 2 months ago.
sounds good, I will send over the pix

use the 'add files' link next to your send button

Customer: replied 2 months ago.
thanks for the help, I isolated the issue in the low voltage (red/white) wires to the A/C, I ran a new wire and the unit is working fine.

Good work!