Very little heat blowing in my Pontiac Grand Prix - need help!


New member
Nov 19, 2021
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So I'm trying to diagnose a 2006 Pontiac Grand Prix GT with the Supercharged V6. It's a super low miler at only 140k kms. The problem is the heat just quit working one day. Along with that the temperature in the gauge doesn't want to stay at operating temperature. It'll get to OT at idle, but once I start driving the temperature gauge will drop. So the car will only blow cool/warm air. I've even had the car at 130km on the highway and it still wont be at OT.

I've replaced the thermostat twice, both OEM. I've replaced the water pump with an OEM one. It did need a water pump as the old one was making noise and the pulley was wobbling. It was also leaking coolant from there through the pulley. It has full coolant. I also bled the system (I think). It's hard to tell if it's actually bled. I've also replaced the heater blend door actuator. I also replaced the HVAC fuse. STILL NOTHING.

It seems like everything I do doesn't solve the 2 original problems of no heat and the temp gauge not wanting to stay at OT. This is literally driving me crazy. People keep saying it's the heater core but the only symptoms is no heat. Both hoses going to and from the heater core into the firewall are also hot. The car doesn't burn coolant/oil or leak anything. No coolant smells anywhere inside the cab, engine bay, or the cars exhaust. And the car also drives amazingly perfect for a 2006.

Anyone have suggestions? Could it be an electrical problem?


Staff member
Dec 8, 2008
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Could it be two unrelated but similar problems?
Rent a IR gun to measure the actual temperature.
Have you checked if you have a heater control valve that is not allowing hot coolant into the core?