Blower fan not working

[earl orchard]

Hi all
My blower fan now does not work at all, before it would sometimes not come on but would eventually come on, now nothing at all. So I pulled the cover from under the glove box, ran a negative to the fan motor and it ran great. I then checked voltage at the plug and would get 14. Volts. What and how do I test further , is it a bad porcupine resistor or ccu unit.
Thanks

[Matt at Pelican Parts]

Sounds like typical symptoms of a bad blower motor resistor. Sometimes they can last years working intermittently before they fail all together. I'm sure there's a way to test it if you know which wires are + input and output.

What is the year and model?

-Matt

[earl orchard]

Sorry my car is a w126 300sdl 1986

[BillGrissom]

More info needed. Model, year, tried pushing low-high-autospeed buttons. Later models have a blower speed relay box which works w underhood resistors box.

[Sugar Bear]

If a negative made it run wouldn't that indicate a bad ground?

[INSIDIOUS]

Clean it up with compressed air and lube it.