bolling

I have 87 vette with automatic heater a/c and the blower won't run. I purchased the car this way. I tested the plugs on the blower housing under the hood and did not get the proper readings on all the wires. The next step is to trace all wires and make sure they are all ok which I did not attempt. I don't really see how possible this would be to do. The next step if all wires checked out is to replace the blower motor control module which cost $125. I would like to know if this is a fairly common problem. I was told this would be a non returnable part so wanted to get opinions first. I would gladly pay it to solve problem.
Thanks

SunCr

Start by jumpering the Blower to Battery to verify it works. Look for a discolored hot wire at the Blower Motor Connector which usually means that's it's dropping volts and heating up - often melting the wire at the crimp inside of the Weatherpak. The crimp can loosen up which causes the voltage drop which causes the excessive heat. Solution is to solder in a new one.

Blower Module gets low voltage signals from the Controls and then amplifies them to run the Blower. That signal is on the Brown or Tan Wire at the Module and is about 2.5 volts for 1; 6 volts for 10. Output is either Black/Red or Purple or whatever is hot at the Blower and should be 4 volts for 1; 12 volts for 10.

Make sure the Module is powered up - that's red on a fusible link from the Starter Motor so it's always hot.

gerardvg

First check the fuses and that the blower motor works, run 12 volts from the battery to the blower motor and make sure the ground is good or measure resistance of the blower motor. It may be burnt out.
Next check the blower relay, it is in the engine bay.
The contacts wear and doesnt make a good connection, replace it if needed. You can pull the cap of the relay, use a small flat screwdriver.

The resistors are in the engine bay, check the resistance and make sure none are open circuit. They only control the lower fan speeds the high speed fan has 12 volts supply no resistance.

Cliff Harris

He has a C68 system -- no resistors or blower relay. It's all done in the blower control module.

bolling

So do you think I should change the blower control module?
The fan will run with 12 volts put to it.

WVZR-1

I would say your money might be better spent initially for a FSM (Factory Service Manual) so you could maybe determine the better approach to this and likely many more issues.

This I believe should be a C68 '87 blower wiring.

Cliff Harris

Check the large red wire on the blower control module connector. It should have 12 volts on it all the time. It is connected to the positive battery cable on the starter solenoid through a fusible link (top left of WVZR-1's diagram).

Disconnect the wire to the blower motor and measure the voltage on the connector with the ignition and HVAC turned on. The voltage will vary depending on the fan speed. I don't know the exact numbers, probably something like 5 volts or so on low speed and around 12 volts on high speed (10 on the display). On my car the minimum fan speed is 03 on the display with the fan switch in AUTO mode but it will go down to 00 in manual mode. I assume 00 would be zero volts on the blower motor.

bolling

Thanks for all the help. I installed a heater control module and now the fan works properly. Now on to the A/C
Thanks again

002Loose

I’m not getting any power on the purple wire going to my heater fan off the module it’s self. Has anyone had this problem before? How do I get power back to it again? Or where does it run to so I can fix the problem. Hopefully someone can help me out. Thank you

jsinga

C68 blower modules are the same on Buick olds and cads from about 86 to 90. I have 2 good ones I got for $5 each at local yard.