1999 Pontiac Grand Prix Vents Hot On Drivers Side- Cold Passenger Side

This controls the temperature of air coming out of the vents. When they go bad, the air stays cold or hot and you cannot adjust it.

1999 Pontiac Grand Prix. When I turn my heat on I get heat on the drivers side and A/C cold temperature coming out the passenger side. Same thing happens if I turn on the A/C.

This is a common problem with a temperature door actuator motor in the dash. A problem with air temp on the drivers side means the drivers side motor is the problem, and vice-versa. You can try removing the HVAC fuses for a few minutes, then re-install and then start car and let it run for a few minutes without touching any A/C controls. This may reset the motors, but will most likely act up again.

Yep, those temperature actuator motors fail all the time.

I’ll try removing the fuses first, If that doesn’t work I’m assuming the actuator motor is under the dash? The air on the drivers side is WARM not hot and the air on the passenger side is COLD, do I have a problem on both sides or is the cool air blending with the air on the drivers side? Right now I am assuming I have a problem on the passenger side.

Well, usually when these motors fail, it is full cold or full hot.Sounds like the main problem is the passenger side motor. For the dr. side just being warm, check to make sure coolant level is up and that coolant is reaching operating temperature. Without a test light and schematics, only real way to check is to tap on motor as changing temp to see if it frees up, or remove motors to see if they move when changing temp. Problem is that with the motor removed, if it starts moving, it will go all the way around and not stop, thus damaging the motor if it was OK to begin with.This controls the temperature of air coming out of the vents. When they go bad, the air stays cold or hot and you cannot adjust it.

Air blend actuator is out!! I manually closed the door and I have heat on both sides. Actuator is on order. Coolant is at proper level and the air is now hotter but I am still not sure it gets as hot as it should. I’ll wait till I go on a longer drive to see how hot it gets. Thanks for your help. :)

Water temperature gauge was fluctuating, replaced thermostat. Air is hot now and gauge holds when sitting still but drops pretty far while driving?? Grabbed hoses to the heater core and one was noticeably hotter than the other. Is this normal or do I still have a problem.

When the thermostat opens, the temperature on the gauge will drop. Depending on how cold the outside temperature is, it can drop dramatically. One heater core hose hot, the other not as much, is normal because the blower motor is transferring heat from the core to heat the car, so the outlet hose should be cooler. Again, the colder the outside air temp, the cooler the outlet hose will be. Even cooler with the blower at a higher speed. Make Sense ?

2001 Pontiac Grand Prix Blow Cool Air

I have a 2000 Grand Prix my air conditioner is blowing cool air but not cold , it worked great one day then the next it wasn’t , the ac clutch is on and its full on freon and all thew fuses are good and the cabin filter is clean ,Just tell me where to start anything would help Thanks Marc

Usually when the air conditioning is blowing cool but not as cold as it should be, there is only a couple different things that can cause that. An over-charge of the system can do this, so you might want to just double check it has the correct amount of R134A and PAG oil in the system. Otherwise, a restriction in the air conditioning system can cause a lessening of the cooling effect. This could be a clogged orifice tube, a bad evaporator core, or even a dirty/clogged condenser that isn’t getting enough airflow across it. If you have access to an A/C machine or at least a set of gauges, this can be of great help in diagnosing the problem. Ideally, you’d like to see about 30-40psi on the low side and about 150psi on the high side when the air conditioning is running optimal with the optimal charge. Of course these readings rise on extremely hot days and get lower on colder days. If your readings are not in that range, you either have a restriction or the incorrect charge in the system.