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HVAC troubleshooting - any guesses?
Posted by: clay
Date: June 27, 2018 03:34PM
older Lennox Heat Pump. Been working fine. Had it inspected and serviced when we moved in 3 years ago. As I recall, they replaced a couple capacitors, but beyond that nothing major. Been working fine since.

Before we left on vacation a little over 2 weeks ago, I set the unit to "Cool", fan to "auto" and set thermostat to 80 degrees, just to keep things from getting out of control while we were gone.

Arrived back home a week later, air is coming out of the vents, but system wouldn't cool. Discovered that the outside/compressor unit was not running. Inside blower is running as expected.

I tested the capacitor in the outside unit, seemed as though the "fan" side was not working, so I ordered a replacement. Arrived today, installed it, nada. I heard a "click" in the outdoor unit when it was turned on from inside. But compressor isn't running, fan isn't running, etc. So, maybe there was something else wrong with the unit.

I'll call the HVAC repair folks if needed, but wanted to see if there's anything else I should check before doing so (so as to avoid the $100 service call+parts). The unit seems to be getting power (checked with non-contact voltage tester), though I know once power comes into the unit, there might be something else going on so that some particular component is not getting power.

Ideas?

Model: hp26-261-1p

The unit is this one: [www.repairclinic.com]

here's the manual for our series: (pdf) [www.completeheating.ca]
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Re: HVAC troubleshooting - any guesses?
Posted by: space-time
Date: June 27, 2018 03:38PM
it seems like you tested the capacitor, so I assume you have a DMM that can measure capacitors. I also assume you tested the new capacitor with the DMM,

if the fan capacitor was not working, it is possible the compressor overheated at some point? is there a thermal protection gizmo you can reset?
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Re: HVAC troubleshooting - any guesses?
Posted by: clay
Date: June 27, 2018 03:40PM
Yes, tested the new capacitor. seems ok.

not sure if there is a thermal protection reset for the compressor. I don't see anything in the manual at first glance...
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Re: HVAC troubleshooting - any guesses?
Posted by: cbelt3
Date: June 27, 2018 04:01PM
Also will the fan run ? My bugaboo my Lennox AC unit is fan motors. I've replaced it three times.
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Re: HVAC troubleshooting - any guesses?
Posted by: clay
Date: June 27, 2018 04:02PM
The fan is not spinning on the outdoor unit. I tried to push the fan blades to see if it would start, and it would not turn on. The blades spin freely.

I just put my ear up to the unit while still powered on at the thermostat, and there is a faint buzzing noise. Not sure whether that is compressor or fan motor related.
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Re: HVAC troubleshooting - any guesses?
Posted by: clay
Date: June 27, 2018 04:04PM
I know that many units have both start and run capacitors. The repair clinic link above shows both for this unit. But I'm not seeing the start capacitor anywhere as I look at the manual or with the side cover of the outside unit off. The run capacitor (that I replaced) is quite clear. But I'm not seeing where a start capacitor should even go. I'm happy to order one, and maybe I should, but seems like my unit may not use one, or it is somewhere really inaccessible...
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Re: HVAC troubleshooting - any guesses?
Posted by: cyclemax
Date: June 27, 2018 04:39PM
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.
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Re: HVAC troubleshooting - any guesses?
Posted by: Bernie
Date: June 27, 2018 04:58PM
Replace the capacitor.
Then call HVAC person if it does not run.




Staunton, Virginia
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Re: HVAC troubleshooting - any guesses?
Posted by: Carm
Date: June 27, 2018 05:03PM
Clay, manual says you have a dual capacitor. Which runs both the fan motor and the compressor motor.
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Re: HVAC troubleshooting - any guesses?
Posted by: cbelt3
Date: June 27, 2018 05:07PM
Clay-
Ooh... yeah. The Dual capacitor was the first thing to go on my Lennox unit. I swapped it and it ran for another six years before the fan motor died. It's easy to remove and take to an HVAC parts store.

Caution.. they might not have one that size.... call around first.
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Re: HVAC troubleshooting - any guesses?
Posted by: TLB
Date: June 27, 2018 05:36PM
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.
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Re: HVAC troubleshooting - any guesses?
Posted by: Bill in NC
Date: June 27, 2018 06:18PM
IIRC, ants sometimes like to swarm the contactor.
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Re: HVAC troubleshooting - any guesses?
Posted by: Grateful11
Date: June 27, 2018 06:37PM
Quote
cyclemax
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.



Grateful11
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Re: HVAC troubleshooting - any guesses?
Posted by: rexs
Date: June 27, 2018 07:28PM
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.
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Re: HVAC troubleshooting - any guesses?
Posted by: bobinmurphy
Date: June 27, 2018 09:03PM
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.
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Re: HVAC troubleshooting - any guesses?
Posted by: clay
Date: June 27, 2018 10:20PM
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.
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Re: HVAC troubleshooting - any guesses?
Posted by: clay
Date: June 29, 2018 01:29PM
update posted here: [forums.macresource.com]
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