This is a 2005 Impala. We have replaced the blower motor itself twice. It’s, again, only randomly working. No pattern. No defrost or heat. Any suggestions?
The problem might be with the blower motor control processor.
It’s mounted next to the blower motor.
I’ll give it a shot and let you know.
Aside from checking the blower control module and harness, it could also be a bad ignition switch.
No experience w/Impalas, but blower motors are usually simple DC motors. The speed they run is proportional to the voltage across the two inputs. 12 volts they run fast, 2 volts they run slow. The controller probably just takes the battery voltage as an input & varies the DC voltage output to the blower motor according to how much airflow you have set on the dash hvac controls. So measuring the voltage applied to the blower motor terminals with a volt meter as you vary the settings is a good way to begin the diagnosis. Could be a problem with the blower motor, the controller, the fuse, or corroded/burned connectors. Make sure the blower cage is turning freely too, not blocked by leaves and debris that have got sucked in.
If you kept the old motors, you can try hooking them up on a bench with any 12 volt battery, just to ensure that they were indeed bad.
There is a blower motor resistor that works in conjunction with the control processor. It will be mounted so that its heat sink is in the air flow from the fan.
In the old days of manual fan speed controls, the blower resistor had a series of resistors, one for each fan speed, so when it failed, you lost one fan speed at a time until none of the fan speeds worked.
In the mid-1990s, heater controls became digital, and the motor resistor is now transistor-controlled. When it starts to fail, motor operation may be intermittent. That is the hottest part of the electronics and is therefore the most likely to fail first. I recently replaced the resistor in a '97 and solved an intermittent blower operation problem.
For this car, the resistor costs only about $35 on line, and it is a LOT easier to replace than a fan.
Well, we bought the parts and we are going to see what happens this
weekend. Thank you all very mush for the help. I think this help narrow
down the problem and save us a lot of time. I’ll let you know how it turns
Okay, well, turns out it was just a loose wire this time. All that for just
a loose wire. Lordy. Since this had been a reoccurring issue, assumption
was that it was something major.
It’s a Christmas miracle, hahaha.
Thanks again everyone. Merry Christmas.