December 26, 2016 at 10:22 am #12901
After years of using the heater/AC in my 2000 Nissan on on setting 4, the blower motor abruptly died. I researched the problem and purchased a blower motor from Rock Auto, and a resistor from O’Reilly Auto Parts. After replacing both, the new motor works on all 4 speed settings, but the air barely blows even on setting 4. I can tell that on a hot Summer Day, this type of performance would not cool the vehicle.
I would like to find out how to troubleshoot to see if it is the new motor, the new resistor or both that are causing the diminished out put of the heat/AC system after the repair. Any advice would be appreciated.December 28, 2016 at 3:26 pm #13201
First, I am assuming that you are referring to the front blower. The speed is controlled by the resistor block. This confirms you have a MANUAL A/C control unit, not an automatic. Any difference in ohms of any of the resistors in the new block, compared to the original block, will alter speeds 1 to 3 of the new motor. Speed 4 of the motor is full speed. If the blower does not produce the same speed/flow of air, you are using the wrong fan/motor combination. Please confirm to me if you used original blower fan with new motor or replaced fan/motor combo.
Looking at the electrical diagram on page HA-148, in position 4 for the front fan, the blower motor is energized with full battery voltage. This means, the resistor block is not used for that speed setting. The block only controls lower speeds from 1 to 3.
If the motor failed by blowing out the main 20Amp fuses. The original motor is in short-circuit. That might also had blown out the internal fuse of the original resistor block. If this was the case, replace the motor, check the fuse of the resistor block and replace fuse if necessary. Use new motor with original resistor block.
If the motor failed in open-circuit, use new motor with original resistor block. Check internal fuse of original resistor block and replace if necessary.
Full procedure for diagnosing the front blower motor starts on page HA-166. With an ohm-meter, please check the resistance of each resistor in the block. Follow the terminal and ohms reference table that is located in manual HA page 171.
Let me know what results you have.December 29, 2016 at 10:12 am #13791
Thank you for such a detailed and thoughtful reply. I am embarrassed to report that I did not understand that the new front heater motor that I bought from Rock Auto could have “dual polarity.” I was wondering why there were two “butt splice connectors” in the package, but am glad I did not discard them.
A kind individual a O’Reilly Auto Parts guessed correctly that the new motor was turning in the wrong direction. It came from factory turning clockwise. When I removed the new motor and tested visually, I saw that for the fins on the squirrel cage, the motor needed to turn counterclockwise . All I had to do was cut and splice the wires to reverse the polarity all is working perfectly now. For anyone else who needs to do this, there are 3 8mm bolt head screws that attach the motor up into the container. The back one is a PITA, but I was able to get a regular small 8mm wrench back there and get that screw in and out w/o too much trouble.
Since I am having some other electrical issues with this vehicle, I will refer back to the detailed instructions you offered here about testing for electrical problems. Thank you again for your kind response!December 29, 2016 at 3:22 pm #13941
I am so happy you got it working correctly.
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