Any advice on DIY home HVAC repair?

Good timing: we're going to be hovering around 100° all week, and my undersized, outdated A/C is on its last legs, I think. Last night it started making a horrible rotational noise, like a bearing is failing. The good news is that my new drummer is an HVAC guy, the bad news is that he's already swamped this time of year.

I'm considering cracking open the case to see if there's anything obviously wrong with the thing. Anything I should be looking for in particular?

Does it even make sense to repair a 15-20 year-old air con? I mean, during the heat wave a couple weeks ago, it could barely get the house below 77°, and it was running 24/7. Maybe it's just time for an upgrade?

I don't know a ton about them, but "rotational noises" make me think it's either the compressor or the fan that's going out. If it's the fan motor, they're super simple to replace. If it's the compressor, forget about it. If it does happen to be the fan motor, make sure to clean out the condenser really well, because if it's stopped up the fan is working extra hard to pull air through it, drastically shortening the life span of the motor.

It's definitely either the compressor or the fan, as the terrible noise is coming from the hot side, outside. Hadn't occurred to me that it might be the compressor - that sounds damned expensive. Oy.

Oh, and if you've got the cash, it probably is time for an upgrade. My AC unit of the same vintage was replaced a year and a half ago, and even in the ridiculous heat wave a couple of weeks ago it had no problem cooling my 106 year old house. My old unit would run non stop in the peak of summer every year. Oh, and my bill is about 1/3 of what it used to be.

But if money is tight and it is the fan motor, just replace it yourself and be on your way.

I had a fan motor fail on me once. I laid a $10 box fan on top of the condenser for a day or two and it worked like a charm. One trip to Grainger and it was fixed in a few minutes, easy peasy. Hope that's all it is.

pinchvalve wrote: I had a fan motor fail on me once. I laid a $10 box fan on top of the condenser for a day or two and it worked like a charm. One trip to Grainger and it was fixed in a few minutes, easy peasy. Hope that's all it is.

That is a fantastic temporary solution.

16vCorey wrote: Oh, and if you've got the cash, it probably is time for an upgrade. My AC unit of the same vintage was replaced a year and a half ago, and even in the ridiculous heat wave a couple of weeks ago it had no problem cooling my 106 year old house. My old unit would run non stop in the peak of summer every year. Oh, and my bill is about 1/3 of what it used to be.

This is exactly the equation we're weighing at the moment. I'm certain we can make massive gains in efficiency by going to a newer unit.

The other night at 0400, I hear "bang bang bang bang" with the AC running and the dog going off. Shut off the unit and went to look. Half a mouse was inside by the fan blades.

Good news is, I think it's "just" the fan on the condensing unit. Compressor starts up separately and sounds normal, but the fan is shaking itself to death. Now how do I go about finding a replacement fan?

Dr. Hess wrote: The other night at 0400, I hear "bang bang bang bang" with the AC running and the dog going off. Shut off the unit and went to look. Half a mouse was inside by the fan blades.

That happened a couple months ago at work. The warehouse guy was putting up parts and heard a clunking from the giant fan in the wall of the warehouse. He went upstairs to investigate and found half of a bird on the floor right below the fan.

alex wrote: Good news is, I think it's "just" the fan on the condensing unit. Compressor starts up separately and sounds normal, but the fan is shaking itself to death. Now how do I go about finding a replacement fan?

Could be that the shaft bearings on the motor are shot. Or it could be a severely out-of-balance blade assembly. Pull the thing apart and check the motor shaft for side-to-side play and check the blade assembly for damage.

alex wrote: Good news is, I think it's "just" the fan on the condensing unit. Compressor starts up separately and sounds normal, but the fan is shaking itself to death. Now how do I go about finding a replacement fan?

Get the numbers off of it and call around to the appliance parts stores (or Grainger, and previously mentioned). One of them is bound to have an equivalent motor. I'm sure an actual HVAC shop will have them, but they're probably going to be considerably more expensive.

More expensive than Grainger? Wow.

The motor/fan unit is generally on 3 rubber isolation mounts in the fan housing. They collapse over time, and the fan will contact the housing, subsequently attempting to "self clearance" with the noisy result you hear.

Open it up, see if the fan drum is remotely concentric in the housing. Shim with washers and short lengths of heater hose as necessary.

If the motor is screwed, Grainger can probably cross-reference. In my experience my local Aireco Supply was cheaper on the stuff I've needed, run capacitors and such.

Found a replacement motor for $100 at a local electric motor shop. Grainger came close but no cigar, and the appliance store across the street recommended this specialist shop. The motor I needed was literally sitting on the counter, as if it was waiting for me. So, sorted.

Thanks for help with my first successful foray into the intimidating world of HVAC, fellas.