Help with furnace??

[[email protected]]

Ok, its getting to be furnace time here in PA. Mine is broke but luckily I can fix that myself, its easy, and the part is warrantied. Thanks Lennox.

But, my grandparents aren't so lucky. They a have a York Diamnond 90 model P2UR. Its a gas furnace with AC coil. Been having nothing but problems since they had it installed about 8 years ago.

2 years ago I replaced the control board as theirs was totally fried for no apparant reason. Last year I replaced the combustion air intake assembly as the "squirrel cage" was cracked severely.

This year, its blowing the 3A fuse on the control board. All my research is pointing me towards a short in the 24V wiring somewhere. As far as I know the fuse only blows when the furnace calls for heat making me think the problem is either in between the t-stat and control board wiring or possibly one of the safety switches that are operated by 24V.

Just curious if anyone here has some HVAC experience and can offer some advice of how to proceed?

 

[zippo6]

Sorry man, I got nuthin'. Best of luck though, no heat sucks!

 

[Mitchell]

""Just curious if anyone here has some HVAC experience and can offer some advice of how to proceed?[/QUOTE]

I have 20 years of experience and moonlight to pay for my bad habits, like my Vmax, Super Magna and good entertainment. Anyway Mike, You are on the right track. The only reason to blow the control board fuse is either a direct short in the secondary 24V system or the board itself. Process of elimination. If you havent tried this already?,,,,,, Kill the power to the furnace, disconnect all the "thermostat-a/c control wires to the control board", install a new fuse and turn it back on. If it blows again, then look for a direct short (including frame-casing wire rubs) on any low vac wire that comes off of it. If you can't find anything then 9 times out of 10 the control board has an internal short in it. Let me know what you find and if I can help you any more with the problem. Good luck!

 

[06VMAXIMUS]

I had a similar problem last year. This is gonna sound stupid, but after checking everything 3 times, it turned out to be the thermostat. It looked and acted fine, but was bad. My friend who is a HVAC tech, was banging his head on the wall trying to figure out the problem. We disconnected all the wires at the thermostat, checked each wire individually, and found the thermostat was the problem the whole time. Just a thought of where to possibly start first.

 

[[email protected]]

Thanks for the advice guys. The worst part about the problem is that it never happens while I'm there. It will run fine for an hour and then after I leave, the fuse will blow. I called them yesterday and it was still working from the day before. It's hard to diagnose a problem when you never see it happen, LOL.

 

[06VMAXIMUS]

Def. different than what mine was doing. Mine would start the purge blower, but than randomly shut off and start over. Its hard as hell to diagnose a problem when you don't see it happen or if its only happening once and awhile. Better get her fixed, its gettin cold around here.. I had to turn my furnace on last night!

 

[jfeagins]

The Heat/air unit on my house is an American Standard. All was just peachy until I added a nicer thermostat with automatic setback features. I bought a Hunter brand and started tripping breakers the first day. Thought I did the wiring wrong and even had pro's come double check me. They said Hunter brand thermo's are junk.

I replaced the thermo with a quality Honeywell, and it works perfectly now.

Also, you mentioned a cracked squirrel cage. To me, that would indicate excessive vibrations in the fan unit. Maybe a fan blade out of balance is causing first the blown circuit board, and now whatever is currently wrong?

 

[kaboom]

The only time I ever had a furnace trip a fuse was when a bat, the winged kind, got stuck in the blower.....

Now I have electric baseboards and a wood stove......

I am no help at all:confused2: