still A/C problem in resistor

[dingzhijia]

Hi BNaylor:

yesterday I got sometime and decided to change my bad resistor. At first i did not install them completely, i just linked the wires of motor and resistor. i turned on the A/C and switched to 1 and found the motor even didn't rotate,unless i switch to 2 or higher then switch back to 1, then the motor seemed working normally. Also, I found the resistor was extremely hot. i knew the resistor need blower motor to cool it, but i just turn on A/C for less than half minute. Is that normal? by the way, there are lot of rust on my motor, probably resulted from previous drain issue.
last time you said i probably have problems with wiring, bad ground or possibly an ignition switch problem, how should I check them

[BNaylor]

What happens when you bench test the blower? In other words apply 12 volts and a ground to the blower electrical connector direct. Does the blower spin up properly and main high speed?

[richtazz]

Blower motors require the most current to get them spinning. Blower switch position #1 delivers the least current. Since that's the only position that won't allow the motor to start spinning, I would say the motor is drawing too much current due to water intrusion and will eventually fail and take your new resistor with it. You may be able to lubricate the motor bushings to get you by for a little while, but it sounds like you need a new blower motor to me.

[dingzhijia]

Originally Posted by BNaylor

What happens when you bench test the blower? In other words apply 12 volts and a ground to the blower electrical connector direct. Does the blower spin up properly and main high speed?

yeah,it seems that the blower spin up at high speed when i switch to 5. i think maybe the rust cause the motor not to spin up at low current

[dingzhijia]

Originally Posted by richtazz

Blower motors require the most current to get them spinning. Blower switch position #1 delivers the least current. Since that's the only position that won't allow the motor to start spinning, I would say the motor is drawing too much current due to water intrusion and will eventually fail and take your new resistor with it. You may be able to lubricate the motor bushings to get you by for a little while, but it sounds like you need a new blower motor to me.

so is it a easy job to lubricate the motor bushing? can i do it myself?

[richtazz]

It's pretty simple to do. Remove the blower motor, and use a 3-in-1 type oil on both ends of the shaft. It will get you by for a while, but the motor is going to need to be replaced.

[dingzhijia]

Originally Posted by richtazz

It's pretty simple to do. Remove the blower motor, and use a 3-in-1 type oil on both ends of the shaft. It will get you by for a while, but the motor is going to need to be replaced.

Ok, thanks a lot. Is there any other things can cause my A/C problem? I mean if i change a new motor the problem will be fixed, right?

[dingzhijia]

today, i connected the resistor to the car without the motor, i turn on the A/C and measured the voltage of each speed. When the A/C was off the voltage was zero for sure. but when i turn from 1 to 5 i found the voltage of each speed is the same 13.92V. i remember bnaylor said only speed 5 use direct 12V from the battery, others use climate control. Is this thing normal?

[bocoogto]

The voltage without the motor connected to the circuit will always be full battery voltage on all speeds. If you connect the motor, there will be full battery voltage on the motor on high speed only.

At the high speed setting, the motor lead is connected to full battery voltage with no resistance in the circuit. As you switch to lower speeds, resistors are in series with the motor lead, so part of the battery voltage drops across the resistor and part across the motor. The more resistance, the less voltage the motor sees and the slower it runs.

[dingzhijia]

Originally Posted by bocoogto

The voltage without the motor connected to the circuit will always be full battery voltage on all speeds. If you connect the motor, there will be full battery voltage on the motor on high speed only.

At the high speed setting, the motor lead is connected to full battery voltage with no resistance in the circuit. As you switch to lower speeds, resistors are in series with the motor lead, so part of the battery voltage drops across the resistor and part across the motor. The more resistance, the less voltage the motor sees and the slower it runs.

oh, you are right, i nearly forgot my physics knowledge. when i measured voltage without the motor, there was no current, so all voltage will be the same. Do you think it is my motor problem that cause the resistor overheat?

[BNaylor]

Your blower motor could be an issue or it may not. If nothing else do what Richtazz suggested and lube it. If it works in the other positions it is probably good otherwise. The blower motor resistor (BMR) pulls a lot of current when everything is connected properly which includes to the blower motor. The BMR is located in the airstream in the lower HVAC enclosure for a reason.

Also, when probing for voltages don't forget there is a blower motor high speed relay in there. It is located on the BMR. In position 5 the blower motor hi-speed relay energizes passing 12 volts supply voltage direct via the contacts and not through the resistor matrix. When probing and checking the lower settings positions 1-4 probably a good idea to remove the blower motor hi-speed fuse. Note: You will lose position 5 for the time being.

[dingzhijia]

Thank you guys, your suggestions are very useful to me.
by the way, i want to buy a cabin air filter. bnaylor, you once mentioned about Bosch Cabin Air Filter. do you know the part No that fits my 01 GP?

[richtazz]

For the cabin air filter, just go to the auto parts store and ask for one for a Buick Regal of the same year as your Grand Prix. The spot is there, but GM never installed one from the factory on a Grand Prix , that's why there's no part number listed.

[BNaylor]

As Rich stated the '97-'04 Regal cabin air filter fits perfectly. The sole reason why I went with the Bosch brand cabin air filter is cost and they work fine. I replace three at a time when I do maintenance on the cars. I replace them annually. The Bosch part number is P3720 and it will run around $11.99 at most Autozones.

[dingzhijia]

i went to autozone, and they told there are two kinds of blower motor fits my car, one is Siemens Part Number: PM2714; the other one is Delphi BM10019.
but Siemens one is not excatly the same as my old one, and the connection to the resistor is different. Delphi is the same as mine but more expensive