HVAC troubleshooting - any guesses?

[clay]

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: https://www.repairclinic.com/Shop-For-Pa...Pump-Parts

here's the manual for our series: (pdf) http://www.completeheating.ca/images/pdf/LennoxHP26.pdf

[space-time]

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?

[clay]

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...

[cbelt3]

Also will the fan run ? My bugaboo my Lennox AC unit is fan motors. I've replaced it three times.

[clay]

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.

[clay]

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...

[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.

[Bernie]

Replace the capacitor.
Then call HVAC person if it does not run.

[Carm]

Clay, manual says you have a dual capacitor. Which runs both the fan motor and the compressor motor.

[cbelt3]

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.