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jfk0024 · Oct 1, 2008, 12:30 PM

I have a Carrier furance model number 58STA/STX and my LED is indicating a Secondary Voltage Fuse is Open. I have replaced the fuse and each time I engage the heat switch on the termostat, the fuse blows. I jumped the wiring on the thermostat and each time, the fuse keeps blowing. I also jumped the wires on the mother board and the fuse keeps blowing as well...

Please advise on any ideas t correct.

KISS · Oct 1, 2008, 02:26 PM

Your jumping is sounding a bit like russian roulette. You really haven't explained what terminals you jumped and under what conditions.

From what I think you did, this is what I think you should do:

Remove the wires from terminals R and W (Call for heat) at the furnace.

Jump R and W at the furnace.

What happens?

jfk0024 · Oct 1, 2008, 05:12 PM

Thanks for getting back to me. Should I have the thermostat set on heat when I do this or just have it turned off...

jfk0024 · Oct 1, 2008, 05:53 PM

I Jumped those two and it works but the two wires are now exposed...

Please advise...

EPMiller · Oct 1, 2008, 05:53 PM

Originally Posted by jfk0024

Thanks for getting back to me. Should I have the thermostat set on heat when I do this or just have it turned off...

If you disconnect the R and W wires at the FURNACE, you have disconnected the thermostat so that it can't call for heat. If jumping those terminals at the furnace still causes the fuse to blow, the fault is in the furnace. If the fuse doesn't blow, the fault is in the tstat or the tstat wiring.

EPM

KISS · Oct 1, 2008, 06:55 PM

Use the forum to reply. You said in a PM, that it works when you jump R & W.

Now you need to move that same check to the t-stat. Reconnect R &W at the furnace.

Disconnnect R & W at the stat. Short the R & W wires. Heat should come on or the fuse will blow.

If fuse blows, I would SUSPECT the wiring. If it doesn't, I would SUSPECT the stat.

It's not a difinitive test, but the idea is that the relays in the stat should all be off.

There are lots of variables, including we don't know what make/model stat you have or if the stat uses batteries.

The good news is, it's not likely the furnace.

jfk0024 · Oct 1, 2008, 07:38 PM

Ho do I use the forum? Sorry about the "stupedity" :)

KISS · Oct 1, 2008, 07:56 PM

Your catching on, but the "Answer this question" box, should probably be "Reply to this topic" for original posters and "Answer this question for all others"

Once someone replies to a question, they automatically get notified by email when something's been posted.

You can turn it off or you can turn it on for specific questions that you didn't reply to, but want to be notified.

Yea, the forum is like a BLOG or question and answer dialog for the most part. Everybody adds their $0.02. Sometimes even the experts learn.

I think you got the hang of it now.