Gas and Oil Home Heating Furnaces - carrier heater

I have an electric Carrier heat pump that's 3 years old. About a month ago, the heat wouldn't come on. I eventually discovered a blown 5 amp fuse on the circuit board and replaced it. Everything worked well for a few weeks. Last night, the five amp fuse on the circuit board blew again. Now when I when replace the blown fuse, it immediately blows again when power is supplied. The motor spins freely. Any suggestions on where to start? Thanks from near Atlanta, GA.

If you have a multi-meter you can check for a short probably in the low voltage circuit.

remove all low volt wires. hook up the wire going to the tstat one at a time starting with red. if it does not blow, do the same with the outdoor wire. when it blows it will tell us what circuit has the short

Hey, guys! And thanks for the suggestions. It's Saturday, and my husband is all set to address the lack of heat issue. Thankfully, we live outside Atlanta, and it's been unseasonably warm! This morning, Richard armed himself with meters and other guy-like gadgets and addressed the thermostat. Surprise surprise. Oddly, the heater and the AC came on. What gives?

Oops, it just blew again. Back to the drawing board. Would it be worth just installing a new thermostat and see if that will work?

Fine out if it is the tstat before you buy one. Just try like Hvac4u said first. Find out where the short is. Tell hubbe to look at the wire schamtic;) ED

We unhooked all the low voltage wires. As soon as I connected the inside red wire, the fuse blew. What do I do now?

Now is this all the wires off the tstat and you put the R on R the fuse blowes???;) ED

Yes.
And when I jumped out the red-to-white on the thermostat, everything seemed to work fine. Time to buy a new thermostat?

was ONLY the red going to the tstat connected at time of fuse blowing?

Yes, only the red was connected.

sounds strange, to short the fuse, another wire would be needed..it could be shorted to ground, finding its way back to the other side of the transformer. disconnect wires, jump r and y at the unit,,,outdoor should come on, r to green, fan. if this wirks, new wire and maybe tstat, but i just do not see tstat being the problem from here,

With hvac4u here all wires off the tstat then jump them. You dont have a C with a wire here on the tstat;) ED

"You dont have a C with a wire here on the tstat"

Huh? I don't understand?
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Hubby is off to get more fuses. Here's what happened in the last round:
1. He jumped red to white; unit kicked on and ran.
2. A few minutes later, this wouldn't work.

He's thinking a short somewhere, but having no luck pinpointing it.

R is the + from the transformer to the tstat. Then we have the C- also to some tstat from the transformer.;) ED

turn off the power, and remove the 2 1/4 screws that hold the board in. do you see any burnt spots on the back?

what ed is referring to is that you must have Red (hot 24 volt transformer) shorted to Common ( the other low voltage side of the transformer) somewhere to blow the fuse...so it almost rules out all but the board, unless the red going to the tstat is touching an electrical box that is grounded, freon line, side of the unit, etc. then it would get back to the other side of your low volt fuse and cause it to blow.

check your PM's i sent you one yesterday.

Ok, don't laugh! Do you mean for us to connect these various colored wires at the thermostat or in the unit in the attic.

The Two Stooges

Oops. We just saw your last post. Where do we check PM's?

If you had ALL the wires disconnected to the thermostat except the red, and it popped, It will also pop without the red connected!
You need to reconnect the thermostat. Then remove the two wires going to the outdoor unit, try that. If it pops again, you'll know the problem isn't outside. Try that first...then remove the low voltage wiring on the indoor unit, and jump R or RH to W and see what happens.

There is always the possibility that someone hung a picture and peirced the control wiring. Especially if the fuse blows without a call....

To simplify things:

1. I started from the beginning and disconnected all low voltage wiring inside and outside.
2. I reconnected each--one at a time--starting with red, white, blue, brown. As soon as I connected the two yellow common wires, the fuse blew.


BTW, when the reds were blowing, I hadn't disconnected the browns and blues.

So, the short is somewhere with the yellow wires?

If you have an ohm meter. with the low wires all off of the tstat and all off the board you can ring them out and find the short. dont you have a wire schamtic there on the unit in the door? look at it ;) ED

I just have this gut feeling that the contactor to the outdoor compressor is shorted. Remove the yellow wire inside the outdoor unit ,and see if it pops. This yellow wire doesn't actually connect to anything in the air handler, only a dummy terminal. Visually check the wire outside and the contactor while your there.