'99 Issue with blower motor?

’99 Grand Prix with the 3.8, non dual climate. While driving for some time I will notice the car is starting to loose some heat in the cabin. The blower motor sound like it is running but only small amounts of heat is coming out of the vent or defrost. I have replaced the resistor last year and it sounds like the motor is running faster at each setting increase 1-5. On 4 or 5 the amount of heat coming out of the vent is not the amount is should be. The issue is intermittent.

Thank you for the help.

clogged cabin air filter?

clogged cabin air filter?

Only if it was owner installed after delivery. The '97-'03 GPs were delivered without cabin air filters from the factory. Even if installed and clogged you'd still get heat.

To the OP how do the heater hoses at the firewall to the heater core feel after sufficient engine warmup? What is the temperature gauge reading at the IP?

Just to clarify do blower speeds 1-5 feel normal such as blowing right amount of air?

I have not checked the hoses.

This does not happen right after startup. The amount of air and temp seem normal.
When we have to take a long drive and the defrost is running on the 1 or 2 setting for an hour or two I will notice the temp in the car starts to lower.
I can change the blower speed from 1 to 5 and you can hear the blower making more noise when you switch from 1 up to 5 but the amount of air coming out of the defrost is not what is should be for the higher settings. There is some air coming out. The temp of the air is correct and warm but the amount of air is reduced.
When this does happen it sounds like the blower motor has a weird rattle.

It sounds the blower motor is going bad. You can remove it to check for any obstruction and bench test it by applying 12 volts and a ground to the input connector.

Is the vent control proper. In other other words when you switch modes does the airflow go to the proper vents?

Yes it does move from the defrost to the vents. That works fine. If the motor was going bad would it still make noise like it is running but not be blowing any air out? It also seems to work fine when the car starts up but after some driving it just seems still be making noise but less air is coming out.

Is the blower motor as fun to replace as the resistor? I am 6'4 and I about broke my back replacing the resistor.

Same PITA process as replacing the blower motor resistor (BMR) since you remove the blower motor to replace the BMR. Three 5.5mm bolts hold it up to the lower HVAC enclosure.

Also, just to be sure check the HVAC accessory vacuum line that comes off the intake system around the firewall and over to the battery and main fuse box area before it enters the firewall and cabin. Check for damage, kinks, breaks or any disconnect. Low or loss of engine vacuum can cause the actuators to act up since they are electrical and vacuum operated.

I had a similar problem shortly after I purchased my 98 gtp, so I removed the blower motor to find that a piece of thin cardboard with spiderman on it had somehow managed to work its way down into the fan so when turned on, the entire dash would vibrate and the motor made this horrid sound like my car was about to self-destruct. So...you never know...especially if there is no CAF.