Blower motor keeps failing?

[Capncark]

Hey all:

So a little history on my issue. I bought my 2009 1500 laramie about a year ago. it has dual zone auto climate. Around 8 months ago the blower motor started to work intermittantly. It finally died for good about 4 weeks ago. I was getting proper voltage at the motor but it was clearly dead. i bought a napa blower motor to replace it. installed it and it worked perfectly up until yesterday. it completely quit while I was driving and has not started working again since. I am still getting full voltage at the connector. i am thinking I got a defective blower but not sure if the problem could be somwhere else. I'm not sure, but could it be a ground connection? how do I test for that? I would just return the blower to napa but of course I cant seem to find the recipt.
Any help would be greatly appreciated

thanks

 

[meedom]

Check to make sure you're getting 12 to maybe 12.5 volts to the motor, if you are, then return the blower
motor for a good one.

 

[crash68]

If you check the voltage going to the motor while it's still plugged in, you should get close to/at least 12V at the plug. If not check with the motor unplugged, if you suddenly have 12V, it could be a bad ground or blower speed resistor

 

[Capncark]

Check to make sure you're getting 12 to maybe 12.5 volts to the motor, if you are, then return the blower
motor for a good one.

Thanks for the reply. I went to carquest and bought another blower motor. hooked it up to the harness and it also does not work. I am indeed getting 12v on both sides of the blower motor. i hooked the old motor back up and after a few minutes it came back on so my guess is I need to look elsewhere in the circuit. I am a bit confused how the motor can be getting full voltage but still not work unless the motor receives 12v directly from the battery and the resistor and switch are down stream from the motor. i should mention I was fiddling with the fan speed control about a minute before it started working again. I tried wiggling the wires in behind the hvac controls but couldnt get it to fail again (Electrical gremlins really grind my gears). Because it is intermittant I am leaning towards the speed control knob unless the resistor could somehow cause total failure even on highest speed. Ill have to wait for it to fail again before I go poking around with the meter again.

 

[Capncark]

If you check the voltage going to the motor while it's still plugged in, you should get close to/at least 12V at the plug. If not check with the motor unplugged, if you suddenly have 12V, it could be a bad ground or blower speed resistor

I'm getting 12v at the motor while plugged in and speed on high. 14.3v with engine running. do you happen to know where the circuit is grounded?

 

[crash68]

I'm getting 12v at the motor while plugged in and speed on high. 14.3v with engine running. do you happen to know where the circuit is grounded?

If your checking that across the two terminals going to the motor, I would have to say that's a bad fan motor. I've seen if only checking one motor wire to ground can show 12V due to a bad ground wire from the motor. Can't help with the ground location but check for resistance to ground(will probably be zero).

 

[Capncark]

If your checking that across the two terminals going to the motor, I would have to say that's a bad fan motor. I've seen if only checking one motor wire to ground can show 12V due to a bad ground wire from the motor. Can't help with the ground location but check for resistance to ground(will probably be zero).

Thanks for the suggestion. I checked each wire independantly using the dash bracket nearby as a ground. both were getting normal voltage. I remember reading that the resistor was on the ground side of the motor. From what I understand it controlls the voltage by pulsing the ground at different speeds to adjust the voltage. If this is true then I would assume one wire would be 12v source and the other lead would be sent to either fan speed switch or resistor. If I could find a schematic it would be much easier to diagnose. Keep in mind I have replaced the blower motor with a brand new part and still no joy. The truck has automatic dual zone climate control so the resistor pack is actually a module I believe. Located in the same area as the resistor usually is. I have also heard that when these modules go it could cause no blower at even high fan speed setting. I may just replace the module and hope its not the speed dial. i imagine the hvac control assembly isnt cheap.