99 Alero 3.4 No heat

The heating system on my 99 3.4. I'm not getting hot air when selected to full hot or defrost, The air is warm but not hot. I do have water flow through the heater core, I have not changed the thermostat yet. Could it be the dashboard control panel, When I place the blower fan to full on, the fan goes off?? any suggestions?

Start by checking fuses to the climate control unit and blower hi-speed.

What does your temperature gauge read when the engine is fully warmed up? Are the inlet and outlet hoses at the heater core warm or hot to the touch?

And welcome to AF.

A bad blower motor resistor is a also a common cause of the fan not working on all speeds.

Thank you for the help. I'll check the fuses, the hoses to and from the heater core are hot. But maybe not as hot as they should be.
I had someone tell me I may have compression air getting into my hot air system . Is that possible and what will that take to fix???
Thanks again..

Hello, encountered the same exact problem with an 04 Aero. 1 of 3 things ARE the culprit. This thing operates off of vacuum.
1. Your engine may not be producing enough vacuum, or the supply:runaround: line is leaking, or another line is off and engine vacuum is low.

2. The control knob on the dash is worn, and vacuum is leaking. OR try pulling out the knob, turn the peg for the knob clockwise 180 degrees, put knob back on. :rofl:

3.(worst case) is the vacuum control at the air mixture 'flapper' in the dash is leaking/stuck. :confused:

I had an Alero with 57k mi and this happened. It was in the dash. Other manufacturers put these contols on the outside to the housing. GM puts them inside the housing on this car, therefore you have to rip the dash apart to get to them.

Dude, 4 year old thread......

Hello, encountered the same exact problem with an 04 Aero. 1 of 3 things ARE the culprit. This thing operates off of vacuum.
1. Your engine may not be producing enough vacuum, or the supply:runaround: line is leaking, or another line is off and engine vacuum is low.

2. The control knob on the dash is worn, and vacuum is leaking. OR try pulling out the knob, turn the peg for the knob clockwise 180 degrees, put knob back on. :rofl:

3.(worst case) is the vacuum control at the air mixture 'flapper' in the dash is leaking/stuck. :confused:

I had an Alero with 57k mi and this happened. It was in the dash. Other manufacturers put these contols on the outside to the housing. GM puts them inside the housing on this car, therefore you have to rip the dash apart to get to them.

Thanks for your response, I have not been on in a while so I didn't see your post and just recently got an e-mail telling me you replied. I did get the problem fixed with a new upper and lower head gasket, Blower resister.
after that, two weeks later my poor alero was totaled when a lady thought a red light ment for her to keep on getting it. needless to say with both occupied the same space at the same time. I guess it was meant to be. I have moved from the alero info to the Acura RSX side of things.