HVAC Keeps Blowing Fuses

your hvac is such a whore.

I had a similar issue once and it turned out the contactor in the outside unit was bad.

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Any idea what might be causing this?

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Is the fuse blowing when you turn the central heat on? If so, do you have gas heat or electric?

What size fuses (amperage wise) if high amp, then compressor is usually the culprit (could just be start-up amps going above fuse rating. Low amp fuses then they are likely for Condensing unit fan or Indoor unit blower fans drawing too many amps

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I has the same symptoms a few years ago. A wire on the outside unit was rubbing against a corner, and vibration had worn the insulation until it grounded.

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I knew it was the fricking squirrels!

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then compressor is usually the culprit

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Are you assuming he's running his air conditioner which is causing the fuse to blow?

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I'm cautious to suggest anything based on (respectfully...) what sounds like minimal troubleshooting skills and knowledge...so I'll first suggest you call a pro before you hurt yourself or burn your house down.

That being said, something is causing the unit to pull too many amps; I wouldn't suggest ignoring it and I also definitely don't suggest to just keep throwing new fuses in. It could be a bad/failing cap, loose wire at the shutoff or panel, something with the motor or compressor causing them to struggle; overall you need to run a few quick tests to check a handful of different things.

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I know. This is really beyond my sphere of knowledge. I can replace a thermostat, filters and the fuses. That's about it. Thing is, I just bought a whole new system 18 months ago. This shouldn't be happening. |

Oh well, I'll get a tech out. Least it's warming up this week.

intermittent problems are a real bitch. If the system is that new then I would hope the company that installed it would fix it on their dime. Not always the case.

Visually looking at all the pinch/rub spots where your low voltage wiring could be shorting out and frying the fuse is a good place to start with something like that.

An good tech with experience with your specific system would be best because there might be a pattern they've seen that could be a real shortcut to the problem.

Fyi, most of the time fuses just don't "go bad". There is a reason it blew and if someone just wants to stick a new one in and call it good, then maybe its time to look for a new guy.


I was out at my BIL last summer looking at a unit because he was having breakers tripping on his unit even after the tech came out. It ended up being a chipmunk chewed bare both high and low volt wires where they left the condensing unit. Not seeing this, the tech decided the solution would be to replace the 40amp breaker with a 50, and bypass the low-voltage safety shutoffs on the condenser. Think it was Friday the the 'ol boy had the weekend on his mind.

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I had the same symptoms a few years ago. A wire on the outside unit was rubbing against a corner, and vibration had worn the insulation until it grounded.

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I’m surprised that some of the wiring on an outside unit is exposed and not inside a cover.

What size fuse you talking about - 3 or 5 amp fuse on the control board in the air handler (you said you had electric heat)? Higher rated fuse associated with the outside unit - thinking you may have a heat pump?

You have Nest thermostat by chance? They are known to cause issues like this - seems your like problem from a year ago that the tech “fixed” might be the same culprit a year later particularly being a newer) system.

If the system is less than year old labor would likely would be covered under warranty, if more than year old probably not, but then some firms might cover if it’s slightly over a year particularly if the problem is the same one that was supposed to be “fixed” the first time around.

TLDR: would help if you provided a few more details on what fuse is blowing.