Hello all,
Heat pump is Lennox 10hpb30-8p. Issues started with neither the outside nor inside unit starting. Thermostat was dead. No light on the control board on the outside unit. Tested the transformer and it showed bad. Replaced transformer and got power to the thermostat, but not the control board outside. Replaced the control board, and it is now powered and the LED indicators show no errors. I also replaced the thermostat while I was at it because we wanted a more modern model.
As it stands, if I turn on cooling on the thermostat, indoor unit runs and blows air, but the outdoor unit never comes on. If I turn on heat on the thermostat, nothing happens inside or out. I replaced the contactor even though the original appeared fine. It's cheap and easy to replace, so why not. Nothing changed, however. Capacitor is also good.
If I manually depress the contactor on the outside unit, the fan kicks on and you can hear the compressor come on.
To the best of my knowledge, everything is wired correctly. I just wired all the new components according to pictures I took and labeling of wires before removing them from the parts I replaced.
There are no manual pressure switches installed, I believe, as the control board only has a jumper where they would be wired.
I'm certainly not above calling a professional, but I enjoy fixing things myself when I can. So if you folks could point me in a direction of what I should be checking at this point, I'm all ears.
Thanks for your time.
It sounds like there's an issue with the low voltage wiring between the furnace and heat pump.
With cooling on, do you read 24V between the Y1 and C terminals at the heat pump? Do you measure 24V between the R and C terminals at the heat pump?
The fact the indoor fan doesn't start in heating mode means there could be another issue. Does emergency heat start the indoor blower and electric or gas heat?
Thanks for the help. To answer your questions:
QuoteWith cooling on, do you read 24V between the Y1 and C terminals at the heat pump? Do you measure 24V between the R and C terminals at the heat pump?
Yes to both. 27 volts on each.
QuoteThe fact the indoor fan doesn't start in heating mode means there could be another issue.
Turns out this issue was the result of me being in too much of a hurry when setting the mode of the newly installed thermostat. With the thermostat mode properly configured, the heat setting does indeed turn on the indoor fan, but still nothing outside.
QuoteDoes emergency heat start the indoor blower and electric or gas heat?
The emergency heat turns on the indoor fan and blows hot air.
It definitely sounds like something in the outdoor unit is interrupting the 24V to the contactor. Is there a jumper between the pressure switch terminals on the main board and defrost board?
And, in cooling, do you measure 24V across the Y1-Out terminals on the main board and defrost board? I'm wondering if the defrost board is the culprit but I would look at the old board you replaced and make sure all the jumpers were reinstalled on the new board.
You'll have to forgive my ignorance, but not sure what you mean by main board vs defrost board. As far as I know, I only have the single board on the outside unit.
But you are correct, with cooling on, I have 24v on Y1 and common at the board, but 0 volts as tested on the low voltage terminals of the contactor. I don't have enough knowledge to diagnose what might cause that (other than a bad board itself, which is brand new).
As for pressure switches, the new board has terminals for a low pressure and a high pressure switch. Each set of terminals has a jumper installed. The old board had terminals for ps1 and ps2, with a single jumper going from one of the ps1 terminals to one of the ps2 terminals. The manual for the unit says to remove this jumper if installing the optional high pressure switch, but makes no mention of a low pressure switch.
I appreciate the help, and if I'm out of my depth, I'll call a technician. I'll certainly check anything you can suggest, however.