HVAC troubleshooting - any guesses?

[TLB]

Same symptoms with my Lennox heat pump, about 22 years old. My problem is it is intermittent. The unit runs fine then the outside unit won't kick. Longest period is 2-3 days before it starts working again. I've paid the $100 a couple of times and the HVAC guys say it tests fine. (It knows when he's coming and starts working again). If you fix it, I'd love to see a follow up.

[Bill in NC]

IIRC, ants sometimes like to swarm the contactor.

[Grateful11]

cyclemax wrote:
You could have a bad contactor/relay. This controls the power to the outside unit from the breaker/disconnect. I had one of these fail on an old Trane unit. The contacts on the low voltage side corroded. Fortunately, my brother works in HVAC and had a spare one on his Truck. Fairly easy to replace.

Very well could be what cyclemax said.

Last Saturday I noticed the blower just running and running for hours on Sat. morning. Went outside and
the outside unit wasn't running. Luckily our closest neighbor owns a HVAC business. I called him and he
was on a service call and had 3 more but said he would stop on the way back to his shop and check it out.
It turned to be and wait for it, a dang Earwig had gotten into the Contacts and shorted them out. He said
he's seeing at least 2 per week right now. He said he had tried to file and sand the contact points but they
just don't last after getting burned like that. He put in a new set of Contacts and a few ounces of freon
and charged us $60. Can't beat that deal.

[rexs]

On our heat pump I replaced the capacitors and relays 2 or three times each.
If you're hearing a click, I would check or replace the contactor/ relay less than $20.
Once after a delivery of carpenter ants/termites in a 3-way soil mixture, one of the big ants crawled between the contact points not allowing the current to flow. I removed the toasted ant and cleaned the contacts and voila everything worked.
On other occasions I had to replace the relay and happiness was easily restored since I had a new spare in my "throw-that-out-over-my-dead-body" Box-O- Stuff.

[bobinmurphy]

Lennox - *sigh* When they first came out with their two stage units I jumped all over it and had one installed. Then over the years I struggled with capacitor issues, ants in the electronics, fans going out, loosing freon (where they couldn't find the leak), compressor stalls going from lo to hi speed popping the breaker (that they never could figure out) and air leaks in the indoor gas furnace requiring a full replacement. I finally gave up and had the entire system replaced a couple years ago with a new American Standard (made here in Texas) that's got a higher SEER, scroll compressor, variable speed air flow, etc, etc. It's been working like a champ and my electric and gas bills are about 1/2 of what they were with the Lennox. (To be fair, I did upgrade my windows and reinsulate with spray foam in the attic, ceiling and exterior walls.

[clay]

I did replace the capacitor. As stated in my post, I'm seeing two different capacitors listed in the parts listing at repair clinic.com, but I'm not seeing where the second one would go...either in the manual or in the actual unit. I'm happy to replace it if I can find it.

the capacitor I replaced is a dual capacitor (common, herm, fan).

I'll open it back up in the morning and look for corrosion or any other spots that might seem obvious culprits. I've promised the wife to call someone for repair if I don't find a quick fix.

thanks, all.

[clay]

update posted here: http://forums.macresource.com/read.php?1,2265379