Non-functioning blower

[Stalker12]

Observation: the blower isn't working. Very rarely, it will work. Slamming the passenger door hard results in about 10% success in getting the blower to function. When functional, the control knob works appropriately.

Analysis: with the OM in hand, checked each fuse associated with A/C and blower systems. All fuses are good.

Conclusion: Issue is downstream.

Analysis: Pulled the AC/climate panel out of the dash. Disconnected the Blower motor switch, and conducted Ohm testing on the switch. Compared results to a new blower motor switch. Results appeared normal.

Conclusion: Blower motor switch is functioning correctly.

Analysis: With the key 'On', the engine off and the A/C climate set to A/C, and later floor heat, attempted to 'jumper' the blower motor pigtail to test the plug. Negative results.

Conclusion: Blower motor connector may not be getting power.

Analysis: Put the volt meter on the 'hot' wire in the blower motor pigtail, with negative results.

Conclusion: The switch isn't getting power off the #2 (black) wire. Check blower motor relay.

Analysis: Swapped blower motor relay with known good relay. No voltage at the blower motor switch plug.


So where do I go from here? I'll do a quick direct wire from a battery to the blower to confirm the blower works. I'm thinking with the very rare functioning of the blower, that I have a short somewhere.

Thanks.

[sheltonfilms]

Common problem is corrosion in pigtail at blower motor resistor.

Stick a needle in the hot wire through the insulation and test again. This would take corrosion out of the equation.

[sheltonfilms]

#2 pin (black) is ground not power.

If you don't have diagrams this is how the motor gets power:

Fuse F1.12 (30 AMP) gets power at all times and feeds Brown/Orange wire to blower motor relay.

Blower controls ground relay and send power from Brown/Orange wire to blower motor via Pink/White wire.

Orange/black wire comes from "ground" side of motor and goes to blower motor resistor.

Now if you have the setting on HIGH. The blower motor resistor is bypassed and it grounds out the ground side of the motor.

You getting fan speed on high?

Diagrams:
http://www.revbase.com/BBBMotor/Wd/D...dPdf?id=123810

[Stalker12]

I failed to mention in the OP that the first thing I did was replace the blower motor resistor with a new unit. Not a terribly fun install (wrong tools on-hand).

Looking back, on my ohm testing, the blower switch had ohm readings of 0.1 to 0.2 ohms. The new switch I used as a baseline reading read 0.5 ohms to 0.6 ohms.

The blower still occasionally functions, but last time, only functioned at about 1/4 of normal output levels. On high, it felt like it was switched to low.

When testing the non-functioning blower, I was unable to detect electrical current coming into the blower switch pigtail.