What happened to my voltage?

[Geoff]

Hey guys 99 tahoe. Blower motor went out. Bench tested blower.... Ground is good....getting voltage at the connection to the blower only when the purple wire is not plugged in. Unplugged reads voltage. As soon as i plug it in the voltage goes to zero. Any ideas welcome...thanks for your time.

 

[SunlitComet]

was the blower in fact okay? no direct or high resistance shorts? what test points were you using when testing for voltage when plugged in and not?

 

[Geoff]

was the blower in fact okay? no direct or high resistance shorts? what test points were you using when testing for voltage when plugged in and not?

Blower works fine when connected directly to the battery. My test points were at the actual connector and pierced the wire a few inches back from the connection to test.

 

[SunlitComet]

and where was the ground of the tester connected?

 

[SunlitComet]

also at what blower speeds does this happen?

 

[Geoff]

also at what blower speeds does this happen?

 

[Geoff]

I tested using the ground connector for the blower and that metal bar than runs behind the glove box. Zero voltage at any fan speed when purple wire is connected to the blower.

 

[SunlitComet]

so let me clarify so there is no mis-step here. you put pos probe on purple fan power feed and neg probe was tried on the blower ground and as well as dash support bar? or the ground connection was tested by using continuity test on those to parts?in case i got it wrong test for voltage at all fan speeds with blower removed and pos probe on blower feed connector and neg probe on blower ground connector. if no voltage seen move neg probe to a dash bar. if still no voltage move neg probe again to a body ground. posts the voltages you get and where the probes were at the time. i suspect the ground is damaged somewhere.

 

[SunlitComet]

sometimes depending on where you probe and what the fault is you might get a false impression of what is wrong.

 

[Geoff]

Did some more testing and this time around i got voltage on each fan speed except on high.....with the purple unplugged. Does this point to the resister?