When I start up my 2017 Grand caravan SXT my HVAC controls are inop. The light for the bottom right mode control, rear defroster, blinks for about 30 seconds to a minute and during that time none of the reminder of the controls are functional. I cannot change the mode setting, the fan will not run and the A/C will not turn on. What causes this malfunction and how can I fix it?

 

Hi, I have a 1997 Grand Caravan and the HVAC control for it has Calibration/Diagnostics and Cooldown tests that need to be run
when the HVAC control is replaced, and the manual says it will flash some of the lights on the panel when the calibration needs to run or has run
but had errors (due to issues with the mode/temperature actuators) or A/C system etc.
For example, on my '97, the service manual says to press the WASH and Rear Wiper buttons simultaneously for 5 seconds, until all LEDs light to start these tests
(and the van needs to be warmed up and running, so it can complete the test, usually within about 120 seconds).
If the cal is successful, the LEDs will go off. But if not, one or more pairs of LEDs will blink simultaneously.

I don't have the service manual for the 2017 but maybe it's a similar situation where the calibration needs to be run before it will allow the AC to run.