Central AC repair?

HarveyH48 · Mar 21, 2014

Got home from work today, the house was a little warm, so figured I crank up some AC. It didn't sound right (loud), and wasn't blowing through the vents. Shut it down, checked the filter, looked good. Pulled the cover, looked around with a flashlight, couldn't see anything obvious, so switched on the fan again. Was noisy, but fan wasn't spinning, shut it off again. Reached in, spun the fan, wasn't seized up, spun easy, turned it on again, fan was spinning, wrong direction though. Figured the start capacitor was bad, doesn't look swollen or leaked. It's rated at 370 VAC, 10 uF, the closest I could find (quick and easy, got a box some place with others), was 330 VAC, 15 uF. It's a 220 VAC system, figured it would be close enough.

The deed is done, working as it should, but a little unsure if it's going to be a safe thing. I mostly work with circuit boards, stuff that won't shock, kill, or burn down the house. This repair was a little outside my experience. Just asking, for a little piece of mind. I don't really know how critical the values, or how much tolerance I have to work with. I don't want to leave a potential house burner hooked up. No guaranty that I have the exact replacement on hand, but will probably dig around and see if I can find that box.

coin chaser · Mar 21, 2014

They have a 10% tolerance and your 50% over the rating. It's not going to fry the motor right away but will cause high heat on the windings if it's a run capacitor. Either way they are less than 10 bucks so just get the right size. The vac rating is not a big deal the uf is what you want to match. Good job though finding the problem as 90% of people would not have had a clue.

Robo99 · Mar 21, 2014

On a new motor, this would not pose an immediate problem, but, your motor has seen some use. You are allowing it 15 uF of capacitance at full draw, where it blew out one that provided 10 uF. The voltage is not going to pose a problem here for this situation. The blower motor may be getting weak and requiring more draw on start up, and the result is a blown capacitor. The one you have used will work, but if the system is older, check on a replacement motor before you really need one.

Playsndirt · Mar 21, 2014

you should replace the capacitor with what was in there a 370vacx10 mf if you don't you will have problems,true capacitorscan operate at a 10 percent plus or minus of the mf but the vac must be what is in there. the air cond suppy house should sell it you,but maybe not at whole sale price.

HarveyH48 · Mar 21, 2014

Thanks, pretty much confirmed what I found on the internet. I order a 10 uf, 440 VAC, should be here end of next week, $9.98 free shipping. I was getting +/- 6% tolerance on some sites I checked, so knew I was way over. The run capacitor sets the phase of the coils in the motor, and controls how much current it draws. I'll keep it set for 80 degrees until the new capacitor comes, look and see if I can find that box. Don't have a lot of confidence I have a closer value. Figured a new one was a better bet anyway, since the ones I have are old, and well used, may not last long.

I've been troubleshooting circuit boards for many years, rarely have to do appliances, but works about the same. The internet rocks though, finding the problem is one thing, fixing it can be a different story.

Central AC repair?

HarveyH48

Elite Member

coin chaser

Robo99

Playsndirt

Elite Member

HarveyH48

Elite Member

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