Hey guys, quick question since I don't know where to start here.

I lost all ac/heating power in my vehicle, to include the defroster. When I do some work (transmission drop, carb replacement, spark plug replacement) it seems to work for about one drive, and then fails to work again until I do something big.

The unit is still getting power because I hear a click and "pshhhhhh" sound whenever I change the heating settings, but I get no air whatsoever regardless of what setting I put it on.

Could it possibly be a bad motor or yet again another blown fuse?

 

You've got a vacuum leak behind the dash.

 

Look at the plugs at the back of the passenger side strut tower. There should be 2 large black block plugs and a tiny little clip that plugs into the blower motor. (black block plugs sit in front of the blower motor) If that isn't plugged in, you'll still hear the vacuum pressure but, won't get air.

If there was a vacuum leak, the car would idle rough whenever the ac was on.

 

If the blower isn't working, it's not a vacuum problem. Don't worry about that just yet.

You have an electrical problem, and a very common one, at that.

Take the AC control head out of the dash. You'll find a harness with about 4 or 5 wires plugged into it (a couple of green, one tan, one light blue maybe, maybe 1 or 2 others I can't recall, that all go together in one direction), and one dark brown wire that goes off in a whole different direction. That brown wire is the one that brings in the power from the fusebox. Follow it up into the dash about 12" or so. You will come to a connector of the most astoundingly stupidt design imaginable; it actually uses the plastic to hold tension on the contacts. I cannot believe such an idiotic violation of every rule of electrical common sense was ever allowed to exist; but w/e. Attempt to unplug it. You will find that it is burnt to ashes, may even crumble in your hands, may possibly have burnt the wire back an inch or 2 in each direction as well. Cut the remains of both ends of it off and replace it with a set of the BIG FAT yellow slide connectors that are about 3/8" wide. NOT the little weenie ¼" ones that are exactly the same as the red and blue ones, except with a yellow barrel; look for the BIG FAT HEAVY DUTY ones. Insulate it well with heat shrink or tape or whatever after you're done, you DEFINITELY don't want it shorting to the chassis.

Once you have done that, you might want to get rid of the other one of the same design in that system. That one brings battery to the high-speed fan relay, and is the reason the HS for the blower quits working while all other speeds (the ones that use the resistors) still work. To locate it, start at the blower motor; find the purple wire; trace it back until it arrives at a plug with 4 wires that goes into the relay which is a small box sort of thing; one of the other wires will be a big fat red one; that wire will leave the relay and go upwards across the windshield cowl toward the driver's side; about right above the pass side valve cover you'll find the connector in question. Replace it the same way as that other.