No heat up front but heat in the rear?
 

Being one of the first chilly days in Texas of the season, I cranked up the temp on my digital climate control cluster and waited to enjoy the warmth... And nothing. The climate control waited for the heat to come so it can turn on the blower motors... Nothing.

After the engine was up to temp, I cranked the blower up and the air was ice cold, the same temp as A/C. If I turn on the rear seat heater, it is hot!

Go through the temperature range settings, I hear the doors open and close behind the dash. Can't really hear anything when it goes from cold to hot on temp unless a door is closing for the zone control or air recirculation.

Looked at the heater control valve under the hood (replaced last year). Could not move the valve lever but after some force, it moved and was free after that. I disconnected the cable and moved the valve manually. No heat.
I leave the cable disconnected and it does not move when going hot to cold or cold to hot.

Coolant levels are good. Engine temps 185-193. What should I check next?

Sounds like a clogged heater core or air in the heater core to me.

Feel the inlet and outlet hoses for your heater core once the car is warmed up. If the inlet is hot but the outlet is noticeably cooler your not circulating warm coolant through it, cause it’s clogged or has an air bubble


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The 'front heat' has a coolant shutoff valve in the firewall, operated by a cable from the heater control. The rear heat doesn't have that (at least, I don't think it's affected by the front heater coolant flow being shut off, but I could be wrong).

So heck that the cable hasn't popped off that, and that the lever on the valve opens and closes when you put the temp control from cold to hot.

Most likely your heater core is plugged. It's a very common issue in these rigs. Lots of years of neglect, broken radiators, and people who don't understand how coolant overflow or degas tanks work.

Lots of ways you can unclog it. My vote the OTC coolant flush gun. May as well flush the entire cooling system while your at it.