He heater/AC control unit on my 1993 chevy truck just stopped working (the lights won't come on). I went to a salvage yard and got a replacement, hooked it up and it still didn't work. I had checked the fuse and it was fine. When I turned the ignition switch and pulled out the fuse there was no spark when I plugged it back in. Is there a additional fuse that I don't know about?

These fuses are for manual hvac. Not only check the fuses, use a test light and check voltage at fuses. One fuse is hot all the time, the other two go hot with key on. Also, check ground at hvac unit, black wire, not shown in picture. good luck.

First. Check all the fuses-focus on the blower motor fuse. The fuse box is located near the hood release lever.
Make sure the slide levers controlling air direction and heat are at the top position. Make sure that the blower switch is on high.
Carefully pull temp control unit out about 2 inches, by removing 2 screws at bottom of unit. Get a test light, and check for current to the unit and blower motor.Make sure the connections to the switches are good.
Check the resistor connection to the blower motor. It is in the engine compartment on the AC condenser housing- at the firewall.
Check all the connections related to the blower motor and make sure there is current to the unit.
A test light will help determine what is at fault. If it is a switch behind the control unit, replace the whole unit. Your local auto salvage yard could have one.
Good luck.

a chevy.

The blower motor may need to be replaced and also replace thre blower relay switch under the hood.

You can try a Salvage yard or just order the knob at a Dealer. I went through the same thing with my 1999. If you look behind the knob you will probably see a crack where the metal clip sits.

My Salvage yards do not want to sell the Knob separate from the whole control unit. Yours may. It will be available at a Dealer and with Patience you can replace it yourself. You will see an irregular clear plastic shape behind the knob and that is all that needs lining up.

replace the ac controler and blend door

You can find a cheaper one in the Junk Yard or Salvage Yards found in your local phone books.
Hope this helps

BAD UNIT.....CHANGE CONTROL UNIT AND TRY AGAIN GL

The battery. Get another one from a salvage yard.

I would suggest changing the control head. You should be able to source a used unit from a local salvage yard.

About to have the same thing repaired or diagnosed today. I'll let you know