I'm still chasing electrical gremlins after the last shop worked on my car. I want to replace the under dash wiring including the bulkhead connector and it's related wiring. After looking at how it's wired, it doesn't seem like a replacement exists. And it seems the under dash side terminates in a multitude of places with no easy way to separate it from the switches and connectors. I think the bulkhead connectors are likely OK, I'm wondering about the wires running to the individual locations. Is there something out there to address this, or is this a trace and replace each wire as needed?

 

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The firewall connector and fuse box are part of the dash harness assembly. You can easily remove individual terminals and wires from the connector but obviously you need to have the dash harness out of the car to do the easily. Once you get it out, replacing individual wires is no problem. It helps to have the correct crimping tool for the Packard 56 series terminals. I use MSD 3506 dies in a generic ratcheting crimper handle, but there are similar dies by Klein and others that cost less now.

 

I am currently working on some gremlins in my 66, I have the service manual which has the color coded wiring diagram in the book. Get one, its starting to make sense now that I have layed under the dash for an hour or two identifying color coded wires and where they attach etc. Now I am starting to have a better understanding..maybe if you did this it may reveal your harness is not that bad or you for sure know its horrible..much easier access ifyou remove a bucket seat

 

Yeah, but the problem is that the fuse box mounts right on top of the firewall connector using the same screws. Once you remove the fasteners, there's barely enough slack in the harness to move the fuse box out of the way to access the firewall connector. Oh, did I mention that the e-brake pedal is right in the way, along with the steering column? Trust me, if there's really a need to replace wires or rebuild the dash harness, pull the dash first.

 

By the way, if you think this is a pain, try working on a 67 Delta. The full size cars from that period don't even have a firewall connector. The engine and forward lamp harnesses are integral with the dash harness and just push through a big grommet in the firewall.

 

67 different from 66? my e brake is in the way, my steering column in the way but I am still able to access the dash plug, headlight switch, wiper switch and ignition switch laying on the floor ..maybe I am misunderstanding what the op is asking? I thought he was referring to under dash harness going to switches etc

 

66 and 67 are the same. From the first post:

Sure you can access it while standing on your head with your arm movement restricted. Now you're going to de-pin individual wires in the firewall connector and string new ones while properly crimping the Packard 56 terminals in that position? Good luck with that. Unfortunately the OP hasn't been terribly clear on exactly what he thinks he needs to change. One wire I'd probably do in place. Six or ten? Not likely.

 

My issues are parasitic draw, no front parking lights and no left turn signals. It's not the rear or intermediate harness, so now I'm into the dash area. This started after the last shop worked on it. I have Vintage Air, EFI Tech, under dash gauges and a few other mods. I think Joe is right, pull the dash, then extract the harness for repair. To minimize down time, I was hoping to just replace factory stuff and add the mods to a new harness. I may now be in the market for a used harness I can rebuild first and swap it in. My fuse clips are crap and need replacing anyway, best to do it all now.

 

Neither of those is explicitly a problem with the bulkhead connector. If the "no left turn signals" means both front and back, that's not a bulkhead connector problem since the rear light circuits don't even run through it.

 

I agree, it looks like the whole dash harness needs to come out now, and the bulkhead connector with it. I'm too old and not flexible enough to lay on my back and try to run it down.

 

Before going through all that trouble, are you REALLY sure the harness is the problem? The turn signals could just be the switch in the column. You can test this at the connector at the base of the column before pulling the dash. To remove the dash you need to disconnect the steering column harness, so troubleshooting will be impossible.

 

I’m a firm believer in “American Auto Wire” for harness replacement. If that’s still on the plate