No compressor in back

[Larro]

New ‘20 36kpts with 2 mach8 heat pumps (low profile)
Back compressor never kicked on
I pulled amps off front and compared to back
All I get is hi lo fan draw and no bump for compressor
I ain’t going topside, and nothing except thermostat to view inside
Any ideas?
Got service appointment 4-6. They are booooked!
Thank you!

[Grumpy]

You should be able access the actual control box by dropping the ceiling assembly from below. You may find a loose connection. The same for the thermostat. I would pull it and check all the connections which probably have wire nuts which may have come loose. You need to pull all the wire out of the wall/cabinet to check.

[RoadrunnerII]

If you have the system with no access or ceiling panel below a/c unit from below its easiest to check the thermostat connections first. As mentioned check the twist on connectors. Know to rattle loose. Otherwise you have to get on the roof remove the cover and start digging to access the connections. Best done be a professional if you can find one

RoadrunnerII
RoadrunnerII

[Larro]

thanks! no underhead access- new fangled central system, which I think will be quiter!
I pulled out the thermostat first and everything was wirenutted securely I thought...
yepper, let the pro climb up there.... I dont bounce worth a doggone.

Thanks for your time. I'll post results in 2 weeks after service call

[poohbear]

No offense meant here, but you do have the tstat set on "COOL " ? I ask as a retired AC guy that didn't keep count of all the calls I went on that tstat wasn't on cool or heat.
If new why isn't dealer fixing ?

[Larro]

oh yessir, you are correct.
this new style thermostat only controls one unit.
it cycles something like fan lo, fan high, fan auto, cool lo, cool high, cool auto, heat lo, heat high, heat auto, then... OFF
i was watching the amp draw thru the main breaker box for each, and only got 3 dif readings.... i think i remember 0.6, 1.6, and zero. that represents lo hi off fan only. never a spike for compressor trying to hit.
i bet a lo pressure switch circuit went open, but i dont have a diagram to choose

thanks so much ill holler when monkey climbs up on top and reports!


ps the xantrax inverter reports 133 vac shore power, but i didnt gauge that.

[Larro]

solved!
dealer found defective freeze sensor.
it now puts out 21 degree drop!
Thanks

[JFlightRisk]

Good to hear. Thanks for updating us.