No rear heat

The place to start is to go to the rear heater core and check the temperature of the hoses going in and out. They should be about the same temperature.

I would use a laser temperature gauge to do this so here is a guide that will help with this:

https://www.2carpros.com/articles/how-to-use-an-infrared-temperature-meter

Basically, if the heater core is restricted then the hose temperatures will be very different and that is a sign that the coolant is going back but not flowing. However, if they are both cold then I suspect the heater core is completely clogged and there is no flow back to the heater core at all.

If this is not the issue, then the control panel would be the next likely thing but here is a guide that will get us a little further with this issue:

https://youtu.be/SNRb6pSwYuU

Please see the attached info on how to replace the heater core because I am going to suspect this is the issue.

Let us know what you find.

Thanks

There were two problems: rear heater core and HVAC rear control valve. The heater core was clogged, and the control valve was stuck close. After forcing the control valve open, I could feel heat from the engine coolant on the input hose to the rear heater core. Then I determined that the core was clogged because there was no heat on the return hose.