Hot Topics: A Bug in the System - Literally

A bulging, burnt out capacitor.
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Air conditioning is a great invention. It allows us to comfortably live through seasons that once had people running for the hills. Technology does that for us in all kinds of ways, and we like to think of ourselves as an advanced society. Still, in spite of all out progress, we’re still at the mercy of a stink bug from time to time.

Original Post: Comfortmaker Heat-Pump – fan not running, making buzzing nose

Tanker06 Member

House has two Comfortmaker heat-pumps, approximately 7-8 years old. (New house, finished in DEC `05). Smaller unit, NHP224AKC2 heats/cools the upstairs. Never had any issues w/ either until yesterday.

I got home from work, went upstairs to change, and noticed the difference in the temp as I walked up the steps. Thermostat (a LuxPro PSD100)(question on this at the end) showed that it was 79 degrees, while temp was set to stay at 76 degrees. I could hear the blower running, and walked over to a vent – air was cool (room temp?), but not cold. Went back downstairs, and into dining room (units sit outside window) to check, and no, the heat-pump was not running. (Knew it wasn’t, as you can usually hear the fans run from anywhere in the room).

Went downstairs to check breaker-box. Nada. Went outside, breaker on exterior box was good. No obvious clues as to any issues. Standing next to it, I could hear a soft buzzing noise coming from the backside of the unit, which then seemed to ramp up, like it wanted to start, but didn’t. It then faded after several seconds.

Doing the Google-thing, I’ve seen several other posts here and there talking about the same issue for various units, and the general answer seems to be that the contactor relay is the problem.

Is there any other trouble-shooting type of test that I can do to verify/disprove this theory? I’m no electronic Einstein, but I did radio & vehicle electronics work for Uncle Sam for 8 years, so I’m not a total electron dud. Is this something that I can replace (I’ve seen several places give descriptions as to where the relay can be accessed), or should I just call the guys who do this on a daily basis and be done with it?

Highlights from the Thread

Tanker06 Member


Reading a similar thread, a poster suggested giving the fan a test spin with a stick or long screwdriver.

If it spins freely, it's probably the contactor or the capacitor. If it's stiff, or will not spin, then yeah, the fan's a good bet.

Went outside, spun the fan with a long screwdriver, and it spins freely.

Uggghhhh!!! Frustrating!

hvactechfw Forum Topic Moderator

NO, not the fan, it is likely a power issue or a bug in the contactor. (I literally mean an insect stuck in the contactor)

PS: Please read "Charging your AC" found at the top of the Air conditioning and cooling systems page.

Tanker06 Member

A bug (six-legged critter) is certainly a possibility, as a handful of dead stink-bugs fell out when I opened the access panel yesterday to look things over. (Will have to see if there’s a way to better critter-proof this compartment once it’s fixed.)

A neighbor mentioned that one of their units had gone down, and it had been the capacitor (there is a single, large silver-colored unit mounted on the unit wall next to the contactor.)

Are there any ‘symptoms’ that would point towards this being the culprit, versus the contactor? A cursory inspection (didn't remove from mount) didn't reveal any burnt wires, or bulges. (Would a bulge be obvious, or very slight?)

hvactechfw Forum Topic Moderator

A bulge could be slight. Viewing the top of the capacitor the posts should all be the same height.

Tanker06 Member

While standing there, thinking long, bad words not meant for Sunday-school, I looked at the installed contactor, and using a dowel rod, poked the contactor. It freely springs in and out. So it's not soldered/fried in place. I had my daughter turn on the thermostat, and the contactor closed, but the fan didn't turn on.

Looking at the capacitor, I'm wondering if that isn't it. The top seems to have a slight bulge, had several dead stink-bugs on top of it, and had a yellow film around one of the posts, as can be seen in the pic. I'm wondering if one of the bugs fried himself, and killed the capacitor at the same time.

hvactechfw Forum Topic Moderator

Yep, capacitor looks bulged. Replace it.

Tanker06 Member

It's ALIVE!!!!

Well, part showed up (might have been able to find it locally, but my schedule doth suck - hard - so it was just as easy), and I was able to get some daylight (w/o rain), and go out to swap out the capacitor.

Sure enough - the second my daughter flipped the thermostat on, the fan kicked in and away it went.

Wifey will be glad to sleep in our bedroom tonight, versus sleeping on the couch in the living room!

Thanks for listening to my issue and helping point me in the right direction!