In cab fan - Chevy and GMC Duramax Diesel Forum
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post #1 of 16 (permalink) Old 12-29-2019, 03:47 PM Thread Starter
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In cab fan

Replaced the resistor next to the blower fan under the passenger side dash a couple of years ago. Went out again about a yr ago, autozone warrantied it no big deal. Just went out again and autozoned warrantied it again a couple of weeks ago. But now it decides to quit blowing again today? Any ideas? Its free to keep throwing the part at it but annoying


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post #2 of 16 (permalink) Old 12-29-2019, 04:27 PM
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Did you ever replace the fan or fan witch? something is drawing a higher load than normal, I would use a meter to check load

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post #3 of 16 (permalink) Old 12-29-2019, 04:32 PM Thread Starter
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In cab fan

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Originally Posted by monkeyman View Post
Did you ever replace the fan or fan witch? something is drawing a higher load than normal, I would use a meter to check load


Im not familiar with a fan witch could you elaborate on what it is and where it is? Check load going to the resistor you mean? I tested the fan the first time i replaced the resistor and that was fine. Also it worked perfectly for a few days after i replaced the resistor this time so i would doubt that it is the actual fan


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Last edited by caleb.broege; 12-29-2019 at 04:51 PM.
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post #4 of 16 (permalink) Old 01-02-2020, 04:34 PM Thread Starter
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Im about to test voltage how much should it be drawing?


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post #5 of 16 (permalink) Old 01-02-2020, 10:09 PM
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I think about 8 amps or so. Look at the fuse that protects that circuit and make sure your motor is 50% or less than the fuse.



You will be checking AMPS, not VOLTS. Most DVOM testers will only be able to test 10 AMPS before blowing the tester fuse, so be careful.
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post #6 of 16 (permalink) Old 01-03-2020, 01:20 PM
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if the winding in the blower motor have a short, it will lower the resistance of the motor and increase the current through it (and the resistors). Im not sure what the factory spec is for the resistance of the motor. The current draw of the motor will be the running voltage of the truck (14.4V) / the resistance in ohms of the motor. so a 1 ohm load will draw 14.4 amps, a 2 ohm load will draw 7.2 amps and so on. If the motor winding is low enough for the current to approach the fuses rating the motor is probably bad.

Alternately, a very dirty squirrel cage will drastically increase the load on the motor, and that will increase the current through the motor, so a cleaning of the squirrel cage may also fix your issue. Personally given how easy it is to pull out, i would start with a cleaning and then you can meter it while its out.

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post #7 of 16 (permalink) Old 01-03-2020, 01:21 PM
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Quote:
Originally Posted by Ron Nielson View Post
I think about 8 amps or so. Look at the fuse that protects that circuit and make sure your motor is 50% or less than the fuse.



You will be checking AMPS, not VOLTS. Most DVOM testers will only be able to test 10 AMPS before blowing the tester fuse, so be careful.
to add to that, its usually a fast blow fuse thats not cheap, so personally id measure the resistance and calculate the current as its safer for the meter.

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post #8 of 16 (permalink) Old 01-03-2020, 02:54 PM Thread Starter
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Quote:
Originally Posted by J83 View Post
if the winding in the blower motor have a short, it will lower the resistance of the motor and increase the current through it (and the resistors). Im not sure what the factory spec is for the resistance of the motor. The current draw of the motor will be the running voltage of the truck (14.4V) / the resistance in ohms of the motor. so a 1 ohm load will draw 14.4 amps, a 2 ohm load will draw 7.2 amps and so on. If the motor winding is low enough for the current to approach the fuses rating the motor is probably bad.



Alternately, a very dirty squirrel cage will drastically increase the load on the motor, and that will increase the current through the motor, so a cleaning of the squirrel cage may also fix your issue. Personally given how easy it is to pull out, i would start with a cleaning and then you can meter it while its out.


What do you mean by squirrel cage?


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post #9 of 16 (permalink) Old 01-03-2020, 02:55 PM Thread Starter
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Quote:
Originally Posted by Ron Nielson View Post
I think about 8 amps or so. Look at the fuse that protects that circuit and make sure your motor is 50% or less than the fuse.



You will be checking AMPS, not VOLTS. Most DVOM testers will only be able to test 10 AMPS before blowing the tester fuse, so be careful.


Just to be clear im testing it at the fuse box correct? Or does it not matter


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post #10 of 16 (permalink) Old 01-03-2020, 03:53 PM
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To test for amps. You either need an in-line amp meter to hook into wire or a clamp on type that just clamps onto one wire. I bought a clamp on type years ago to chase down a parasitic draw.

The other thing I found was on a 2010 canyon. There is a grounding block under the hood that a bunch of circuits use to ground with. It was ok however and the trouble was in the wiring harness just upstream of the motor in the dash. The connector was burnt there and was shorting when it bounced around intermittently. I just bypassed the plug with a splice and it's been good since.
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