Fan Blower resistor problems -replaced 3 in last 3 months

Hello,

I've replaced the fan blower motor and new resistor. Did not pull the old resistor out just pulled the wiring harness off it and connected the harness to the new resistor and let it hang down under the dash. After one week, I lost fan speed 1 thru 4 but speed 5 was still working. I then replaced the resistor again. This resistor lasted one month because fan speed 1 thru 4 stopped working again. I've just gotten a replacement for this resistor but before I put it in can someone give me some help why this may be happening.

Welcome to AF.

Common problem. Bad ignition switch and harness assembly.

You really need to place the BMR in its correct location so it can be kept cool. resistors create heat which needs to be cooled by the air moving from the BM. you might be losing these do to excessive heat.

You really need to place the BMR in its correct location so it can be kept cool. resistors create heat which needs to be cooled by the air moving from the BM. you might be losing these do to excessive heat.

I also thought it could be what you replied (install the BMR in its correct location) but how does the resistor keep cool in the summer when it is 80 or 90 degrees outside?

I received another reply to this question that said it may be an ignition switch and harness problem. Do you think this could be the problem as well? If yes, how would I go about checking it?

Thanks for your time and reply

Troy makes a good point. The BMR gets much hotter than that due to the amount current being drawn during operation so airflow will help cool it. Try the BMR but installed properly. If that doesn't work then replace the ignition switch. Just do a search of the dozens of old threads we have on the issue using keywords ignition switch, blower, resistor, etc. What happens is the contacts get carboned up or arced out causing a voltage drop of the 12 volts from the ignition switch to the climate control unit.

Or since you've had so many BMR failures or what appears to be BMR failures do the ignition switch. Good luck and let us know how it turns out.

Could the blower motor cause the BMR to fry if it was drawing more current due to bad blower motor bearings?

Is your rubber seal above the blower motor and under the air intake shroud hanging down allowing rain water to hit the hot resistor- shorting it out? Another very common W-car problem- wet carpet will be the norm if seal is off the bracket...

I also thought it could be what you replied (install the BMR in its correct location) but how does the resistor keep cool in the summer when it is 80 or 90 degrees outside?

I received another reply to this question that said it may be an ignition switch and harness problem. Do you think this could be the problem as well? If yes, how would I go about checking it?

Thanks for your time and reply

When mounted in the correct position, the BMR is in the airflow created by the blower motor itself. That is what keeps it cool versus just hanging under the dash.

Also to answer doctorhrdware's question, Yes. A blower motor that is drawing too many amps due to bad bushings/bearings will also cause premature BMR failure. If there is any water intrusion evidence as mentioned by brcidd, this could also be a cause of original BMR failure, but no so much from the failures when it wasn't mounted properly as I doubt water would reach it just hanging under the dash.

Personally I doubt the issue is a bad blower motor. The best way to test the blower motor is run fan position 5 (hi-speed) which uses direct battery supply 12 volts and not the resistor matrix . If the blower motor is bad it should pop the fan hi-speed fuse and you will see it act up or have reduced airflow at the vents.

I agree Bob. I doubt that's the OP's issue, so I should have mentioned that in my post. But it could....soooooo...

Just pulled my blower motor resistor due to only high speed operation. Failure was caused by dead leaves packed around the resistor, blocking cooling airflow. Apparently they got in through the air intake.

Just pulled my blower motor resistor due to only high speed operation. Failure was caused by dead leaves packed around the resistor, blocking cooling airflow. Apparently they got in through the air intake.

Welcome to AF.

Thanks for participating in the discussion. Do you have a cabin air filter installed?

I haven't had a chance to investigate further. If it does, it's obviously missing or a total failure at its intended function! :smile:

I haven't had a chance to investigate further. If it does, it's obviously missing or a total failure at its intended function! :smile:

What year is your Grand Prix? For example '97-'03 models did not have a cabin air filter installed from the factory. It has to be owner installed or after delivery. It will help keep the garbage out to include water intrusion. You can remove the passenger side plastic cowling at the lower part of the windshield and look at the HVAC air inlet to see if you have one.