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5 amp fuse in Carrier heat pump blows

I had to replace my circuit board due to it being fried. I determined the reason it got fried was due to it having a 10 amp fuse installed instead of a 5 amp. I labeled all the wires as I removed them from the board just to make sure not to get the crossed in the reinstalling. Now the 5amp fuse on the ICB in the air handler blows as soon as I apply power. I have tried to ring the wires but I really do not know which wires should ring to each other or if none should ring together at all. Any one have any advice?

Reply to
brobinson48
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Ring?

Maybe you should put in a 10 amp fuse?**

Seriously, what size fuse did it come with?

How did you determine 10 was too much?

When the board failed, did the 10 blow at all?

**Or 6 or 7 or 8 or 9.

Remove NOPSAM to email me. Please let me know if you have posted also.

Reply to
mm

What was the specified fuse size? If it was 5 amps and now it is blowing 5 amp fuses, then there is something wrong down stream from the fuses. Hard to tell from here what that might be. What all runs off that fuse? Does it include some sort of motor. Maybe that motor is drawing more current than it should.

Reply to
Joseph Meehan

This is usually caused by a short in one or more of the wires somewhere between the air handler and the outdoor unit. First, visually inspect all the wiring to see if anything has been chewed through by rodents. Next, unplug the air handler, pull the disconnect at the outside unit then take the wires that are on the contactor, remove them and twine them together. Go to the air handler and locate the same two wies and ohm across them with an ohm meter/continuity tester. With an ohm meter the proper reading should be OL or some very high resistance, in the mega ohm range. With the continuity tester there should be no tone. If you get very low ohms or a tone then you have a short. If these wires check out then repeat this process with the rest of the wires. There should not be continuity between any of the wires. The trick with a heat pump is there are a lot of wires which makes for several testing combinations.

Reply to
Al Moran

Ok, it's 4:00 am, so shoot me. If you twine any two wires together you should get a tone and/or very low ohms, otherwise there is a short.

Reply to
Al Moran

What was the specified fuse size? If it was 5 amps and now it is blowing 5 amp fuses, then there is something wrong down stream from the

fuses. Hard to tell from here what that might be. What all runs off that fuse? Does it include some sort of motor. Maybe that motor is drawing more current than it should.

The 5 amp fuse should be 3 or 5 amp, depending om model. It is an automotive type fuse and protects the low voltage circuit, including the transformer. If the fuse blows you have a short in the low voltage circuit. The other possibility is if the contactor has rust or dirt on the armature. That will cause the contactor coil to draw high amps just like a motor that is just starting. If the reversing valve coil fell off the reversing valve, it would do the same thing. The stuff on the contactor armature (pole pieces) is called swarf.

Stretxh

Reply to
Stretch

Confucious say never give advice at 4:00 in the morning. Let me start over. The first advice I gave you will only determine if any wires are open, or OL. To find a short, just remove all of the wires between the air handler and the outside and DO NOT twine them together. Go across them two at a time. If any are shorted you will get a tone or little/no resistance. Have I thouroughly confused you now? I confused myself, that's for sure.

Reply to
Al Moran

Fuses don't protect electronics, they protect wiring. Your electronics will fry long before a fuse blows. The fuse may also be used to protect traces on a circuit board. Either way, the fuse size is not the *cause* of anything.

Reply to
dnoyeB

Mr. Meehan No there is not a motor. But I see you are delving into areas you know nothing about again. what he needs to do is call a pro to check it as there is quite a bit of control circuitry there. Please don't start throwing out you misinformation again.

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Reply to
hvactech2

I want to know what the outcome is on this once the OP gets it repaired, but I'll bet if you take the wires off the terminal block and test each one individually with an ohm meter, the white wire going to the outdoor unit will show continuity to ground......

Reply to
Dr. Hardcrab

Thanks for all the advice. But the winner this round is Dr. Hardcrab. The white wire was ring to ground. Checked the outside unit and the insulation was just rub off enought to short it. Thanks Again.

Reply to
brobinson48

Thanks for all the advice. But the winner this round is Dr. Hardcrab. The white wire was ring to ground. Checked the outside unit and the insulation was just rub off enought to short it. Thanks Again.

Reply to
brobinson48

hvactech2 wrote: ..

Thank you for your advice. I assure you I will give it all the attention it deserves.

Reply to
Joseph Meehan

Hi, I suspect your orignal problem was not in the logic board. Wrong fuse cooked it and the problem remains. If you keep trying without finding out, you may blow replacement board too or it is already cooked(or partially) as well. Usually when you replace borad like this you move over wires one by one between two boards. You really needs a schematics for trouble-shooting. And must have a DVM or good analog multi-meter.(careful with this around IC chips) Good luck,

Reply to
Tony Hwang

Over sizing the fuse allows the board to below instead of the fuse. What a shame.

Reply to
Stormin Mormon

Not sure what you mean "ring the wires". What are you doing?

Since the board blows fuses, aparently something is short circuit, some where. with some knowledge of wiring, you ought to be able to isolate some wires, and test for shorting.

Reply to
Stormin Mormon

Below?

;-]

(I know what you mean)

I went on a call one time because the customer's heat pump stopped working and he smelled smoke. When I got there, the board was fried. He swore he didn't touch it, but laying on the floor beside the air handler was two empty cases od car fuses. You know. The "multi-packs" that have a 3, 5, 10,

15, and a 35 amp fuse in them? Well, I guess he ran out of the 5 amp ones and tried all the others. The one still in the board didn't have a rating and I was not sure of the brand, but the common name for the "fuse" is a paper clip.

"I never touched it"

Yeah, right......

Reply to
Dr. Hardcrab

Hmmm, Voluteer fuse brigade must have come for the guy's aid.

Reply to
Tony Hwang

Grandpa wore his suit to dinner Nearly every day No particular reason He just dressed that way Brown necktie and a matching vest And both his wingtip shoes He built a closet on our back porch And put a penny in a burned out fuse.

Reply to
Dr. Hardcrab

I'ze be hanging in de sittee to much, massah crabbie! Yassah, dat boad, she below ou reel guud!

Thanks for a smile. Yep, like the one I heard some years ago. Five amp fuse lasted about a week, so he put in a thirty and figured he had six weeks use out of it.

Mighta been a Turtle tale, one of his customers. Can't remember.

Good catch on the spelling. I'll have to get Smell Czech

Reply to
Stormin Mormon

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