1969 Mach 1 Air Conditioning Stopped

[1969Mach1_428CJ 11]

Before I start tearing my dash apart does anyone know, from easiest to hardest, how to troubleshoot why the heater blower switch suddenly stopped working on my 1969 Mach 1.  One day the blower fan, heater, and air conditioning worked and the next day nothing worked.  Did not do any wiring or body changes when this happened.   I  did the obvious and checked/ replaced the 30 amp fuse already.  

Any help would be appreciated.  Thanks.

[det0326 179]

If you can get to and remove plug from blower switch (I can on mine) then remove it, turn ignition switch to acc and check yellow wire on plug for 12 volts. if you have voltage on yellow wire problem will be switch or associated wires going to resistors on heater box beside blower motor. Could be blower motor itself. If you don't have voltage on yellow wire problem will be from plug back to fuse block itself.  I have know problems with the fuse not making good connection in the fuse block also. To check that you can check voltage on the fuse it self. With acc on should be 12 volts on both sides of the fuse  to ground.

[bigmal 225]

Also try a multi meter on the fan switch. I just replaced mine and it fixed the aircond clutch problem I've been chasing. 

[danno 128]

You might check to see if the AC compressor clutch turns on.  Turn the car on, and put in the AC mode, and fan on about medium speed.  The AC clutch should engauge. If it does, that tells you the power is getting to the fan switch. 

What is common is for wires to break, or contacts in the fuse block to corrode. You need to check to see if you have 12volts on the yellow wire on the fan switch. Also check to see that the connection to the resistors did not get disconnected.  It is behind the glove box somewhere.  If you haven't been in there dinging around, that is probably not it.