Last winter we didn't have any issues with the heater, no issues this summer with the A/C but now that its cold out and need heat, of course there is an issue.

After letting the van warm up and while driving, the front vents blow out heat fine, but the rear vents only blow out cold air.

I've turned the rear vent control off from the front panel and tried it with the rear vent control settings on hot and setting the front panel so you can control it with the rear panel and still cold air.

Any suggestions?

 

I have had actuator issues with those but unfortunately, no calibration that you can do to verify it, will have to be done with a scan tool.