I recently purchased an 07 TL with 237,000 miles on it. Come winter time, car has no heat, most of the time. I have flushed the heater core, changed the thermostat and the water control valve. I can’t seem to get heat and when I do it doesn’t last long and is not hot or even close to hot. Any suggestions? I’ve read through some threads and got some great ideas to try but it’s cold and I don’t want to work outside any longer than I have to. Thanks in advance

 

See if you can get the self-diagnostic codes from the HVAC. I clipped the relevant pages from the service manual.

 

Yeah I tried that too, nothing came up

 

Radiator filled up to top with coolant, warm up to temp and heater on full hot,
both hoses at the firewall, heater core in/out hot?

 

Yes rad is full, heater hoses hot. I’m going to disconnect the cable from the hcv and wire tie it open. I was thinking maybe it was closing on my trip home. I’m not sure though, my car never has heat. Only once or twice I’ve had heat.

 

If all hoses are hot, I would watch to confirm the HCV moves and get under the dash to watch the blend doors. If the blend doors aren't moving, the HCV won't open.

 

If both heater hoses are hot, I'd say no problem with the coolant flow, so I'd check the mix/blend activator door.

 

So after I let the car heat up, the lower hose wasn’t hot at all. Changed the newly replaced thermostat, now the out heater hose is cold. Going to flush the core again. I think when I changed the hcv some of the soft brittle plastic got into the core