I am trying to get the old wiring harness for the headlights, blinkers, and horns unplugged from the firewall of my 1972 Cutlass. I have included the picture of it. It has not budged with just trying to pull or pry it loose. I have loosened the bolt between the 2 plugs, but that seemed to loosen the whole fixture that is mounted to the firewall. I am learning as I go on this project, but I do not want to destroy anything and make more work than I already have to do. Any advice would be greatly appreciated.

 

Undo the screw completely and pull the plug off.

 

You're on the right track. That screw is fine thread and fairly long, so it takes forever. Hopefully, you unhooked the battery, first. There are live wires terminated in the plug. Yes, it holds the fuse box on the inside, too.
If you're going to have it apart, you might as well clean all the old crap out, and put some new dielectric grease in. The terminals are Packard 56-style, if you need them.

 

The fixed part of the connector is held to the firewall by the same bolts that hold the fuse block in place - the connector is sandwiched between the fuse box and the firewall. That center bolt only holds the mating halves of the connector together. You have to completely unscrew it. It should be captive in the connector and not drop out when unbolted.

 

As has already been described (above). Long fine threaded bolt/screw.

 

As Joe stated, the fuse block is screwed to the firewall from the cabin side. On the engine compartment side there are two harnesses that nest together; the passenger side of the fuse block contains the engine circuits (alt, coil, oil & temp senders, etc.), the drivers side contains the lighting circuits (headlamps, turn signals, horns). Here's a pic.

Rodney

 

The factory used some sealer to seal the harness halves from the weather. It’s probably gotten hard and set up solid after 50 years.

Use a heat gun or hair dryer to soften it up. Hopefully between heat and some wiggling it will come lose.

 

Thank you all VERY much for the information. I am glad I went to working on the suspension kit installation when I got mad at trying to unplug the lighting harness. I most certainly would've destroyed something. Vintage Chief, what manual are those wiring pictures from? I need to find page 134 to see where the brake switch distributor assembly is. That wire was not plugged in to anything when I got the car. Thank you again for all of the help.

 

1972 Product Information/Description Manual AKA Factory Assembly Manual. Get in touch w/ member Hairy Olds he most likely has a copy for sale >> https://classicoldsmobile.com/forums...airy+olds.html

 

 

72 Wiring Diagram >>> #3

 

Thank you all for your help. got the old one out and the new one in. I ran the positive battery cable and the wiring harness under the clips on the fender well.( I did not print off the diagram) I will remedy that when I get back to it this weekend. Thanks again for the wealth of information shared by all.