Heat, fans, and AC

Posted by Nate in Projects.
Sunday, July 16th, 2006 at 8:27 pm

Whew. Currently 90 degrees outside, 64% humidity, and it’s 8:30 – when you get up at 5:30, that’s almost bedtime. And it’s way too hot to sleep like that, at least without fans. Or, better yet, air conditioning. Yeah, that would be nice. I can hear our neighbor’s unit kicking on as I write this, pumping delicious cool air into his house…

Not in the cards for us, it seems. Last night, Sierra and Karen and I were sitting on the new deck bench enjoying the breeze when there was a squealing sound from the external AC unit as it tried to turn on. That can’t be good, I said, rising to check on it – yeah, agreed Karen, I heard that before but I thought it was our neighbor’s. Uh oh…

Sure enough the fan wasn’t running. I put my hand on the frame over the fan and it was hot, way too hot to be good. Crap. Went inside and shut the thing down. It was approaching 90 in the house last night as we went to bed but some well placed fans (ceiling fans are amazing, too) and everyone made it through the night.

This morning we woke up to rain – a saving grace, I suppose, since it kept our garden and lawn alive, and probably lowered the temperature for the rest of the day, but we’re currently paying the price in terms of humidity. (Yesterday never got too bad since it was only 30-40% humidity.) The rain also kept me from exploring the AC unit (after of course flipping the breakers both to the unit and the internal blower)… Which in turn kept me from discovering the delightful picture to the left: a blown capacitor. Damn.

The downside to finding the capacitor was now I wanted to replace it – while shut in by the rain I’d been searching for the manual for the unit, no go, and finally spending all my time on this incredibly useful site. I’m fairly confident (barring the actual motor being blown by the strain of trying to run last night) that replacing this capacitor will restore the unit to its cooling glory. But what the hell was the rating on that capacitor?? The oil and gunk inside had fused to the paint on the side when it blew, and unfortunately even carefully cleaning it removed the all-important stamp like you can see on it’s pair above left.

Still, by comparing stamps between the two I’m confident it’s a 3mfd 370 VAC capacitor, probably readily available from a local motor repair shop – I’ll call around tomorrow and see. I also found the schematic at left on the inside of the unit – we are dealing with a 100% rock steady 1976 air conditioner. Whoa. (check the bottom right of the drawing).

Anyway, I figure since the cap is probably only 8 or 9 bucks it’s worth a go. The motor at left is probably a bit under $100, so hopefully that’s not blown too. Once again, having a bit of trouble reading the vital stats, but I guess that’s what you get from an AC unit older than me…

The last bit of bad news is the motor "suspension". It sits upside down, hauling air in through the sides of the box, through the heat exchanger, and blasting it up and out, so it needs to hang level and be supported from above. For whatever reason it’s not bolted to the top of the unit, but instead attached with twisted steel cable – and two of the four are rusted through. My theory / hope is that the motor is ok, the sound we heard was the blades scraping on the housing after the support cable broke, and the resulting current draw blew the capacitor after which everything fell back into place but stopped working. Replacing the cap will cure everything.

At least that’s the hope. For now I’m only investing in a capacitor and some hardware to re-secure the motor… If that fails and it looks like the motor itself is bad, well, maybe time to shop around for a new unit. But in the meantime, if we can get a few more years out of this one, why not? I’ll probably get someone in to test the pressure on the system, make sure it’s as efficient as it can be on that end, but really if an $8 part, some research, and sweat can fix this I’m not going to replace the whole unit yet.

(plus, if you haven’t figured it out, every time something breaks it’s not only a hassle, it’s a freaking personal challenge. :)

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2 Responses to “Heat, fans, and AC”

  1. Anonymous Says:

    Hope that works for you, but if the unit is that old it’s probably not very efficient—plus it just might be one of those that still uses freon which has been banned for years now.

  2. Rick Says:

    Ahh, the joys of home ownership continue! You’re good though – taking it as a personal challenge and learning too. We’re getting our hot water heater replaced this week. They don’t build them to last anymore – average life now is 8-12 years, whereas in the past it was twice that. Progress(?).