Hi!

I have a Payne PF1MNB air handler unit. Came home today and the fuse on the control board (board replaced <2 months ago) had blown. This has happened one other time (after the board was replaced) and when i replaced the fuse it worked fine. Today, after I replaced the fuse, it blew immediately once the a/c kicked on. Replaced the fuse, blew again. Replace fuse, blew again. Replaced the fuse, this time left the system on "off" and fan on "on" and the fan has been running. I haven't tried heat. I have no idea where to start looking for the trouble. Any suggestions??

 

Sounds like you may have a short in the low voltage side going to the outdoor unit.

Undo the Y wire going outside, and leave Y from t-stat on the board and see what happens.

 

Is there a difference between types of fuses that fit in the control board??

I'm asking because I the fuses that blew came from a vairety pack of Busman fuses. On the back it said "for 12 volt automotive only." I went to Radio Shack to find an indivual pack of 5 amp fuses, and this package said "Fast acting - Automotive 5 amp 32 volt fuses. I figure, why not - try one. I put it in and that A/C seems to be running fine. Do you think that was the problem? Should I still have someone come and check the unit in the AM.

Thanks for the advice!

 

32 Volts in Automotive?? I've never heard of it..

I wonder if it's max rating is 32 volts??

When was the last time you had someone go over everything on you A/C to make sure it's all up to snuff??

If has been awhile, or never had it done, may not hurt to have it checked over.

 

Is the new fuse at least safe to use?? It's working now, and I'd kind of like to have it work tonight. I called the A/C repairman to come in the morning.

They checked alot of things the when they came to diagnose the control board problem - contactor, gas level, coil conditions. Is there anything else I should have him check for tomorrow?