Dometic AC Zone 2

[Heir_Max]

My rear ac/furnace, zone 2, will not show on the thermostat. With the 110 AC breaker on, the AC runs with no control. I have tested 12 volt at the thermostat, purchased a RJ11 tool and ran a control line from Z1 to Z2 control. Same thing. Do you think the control unit (thermostat) is bad or the control board in zone 2? Thanks for helpful answers. This is the older 4 button system.

[sdianel_-acct_c]

the above reset procedure that Chris Bryant listed above worked for our back AC. Worth a try.

[Chris_Bryant]

I would say you are correct about the stuck relay- I would give it a calibrated whack.

[Heir_Max]

Chris, I have tried everything except switching from zone 1 direct to zone 2. When I ran the control cable from zone 1 to zone 2, the relay quit clicking but the unit would still come on when I turned the 110 breaker on.

[Chris_Bryant]

Do the fan and mode buttons work OK? Those buttons get flakey. There are several things you could try- disconneting zone 2 and switching zone 1 to zone 2, then see if it shows up. I would still try hooking it direct to zone 2- remembering to reinitialize every time:

The reset procedure is as follows:
a. Turn the ON/OFF switch to ON. The display light with
data should come on. If the light and data are not there,
see Section B2 Cable Assembly.
b. Depress mode to activate display light.
c. Depress the bottom two buttons (up & down) together.
d. While still holding the two buttons add the third from the
bottom (mode) , hold all three for a few seconds.
e. Release the third (mode) button.
f. Release the bottom two (up & down) together.
g. Depress the mode button. The display light should be
off. If not, repeat steps 2 through 6.
The control should return to the default setting of 68oF for
heating mode and 72oF for cooling mode.

This from this pdf of 4 button troubleshooting.

[Heir_Max]

Chris, I'm thinking it is the control board with the start relay fused in the closed position. The thermostat works perfectly on zone 1, but will not read zone 2.

[Chris_Bryant]

Did you reinitialize it each time you made a change? Have you checked the dip switches on zone 2? I would also try running the thermostat on a jumper right to zone 2.
Regardless, it shouldn't run with no control.