Wiring Harness Question

[Tristantinus]

Hey everyone,

So I am working on basically cleaning up my 75 fiat spider. I am not sure what the previous owner has done in terms of rewiring, and i am just a lil grossed out by the state of the wires back there.

I was curious if anyone in here has worked on removing the entire wiring harness for clean up, labelling and repair. I was hoping to remove everything, use the wiring diagram to label anything that isnt labelled and then replace any bad wires etc.

Any detailed help would be extremely valuable.

[baltobernie]

It is certainly possible to do what you're describing. Many of the multi-pin connectors are polarized and only fit the correct mating one. The difficulty is usually the sad state of the harness you've got to work with, as you have discovered. It's not too difficult to determine which OE circuits (if any) you wish to eliminate, the usual ones related to emissions devices. Armed with a blown-up, color-coded wiring diagram specific to your car, this would make a good winter project.

[Tristantinus]

It is certainly possible to do what you're describing. Many of the multi-pin connectors are polarized and only fit the correct mating one. The difficulty is usually the sad state of the harness you've got to work with, as you have discovered. It's not too difficult to determine which OE circuits (if any) you wish to eliminate, the usual ones related to emissions devices. Armed with a blown-up, color-coded wiring diagram specific to your car, this would make a good winter project.

Thank you!!

How difficult is it to remove the entire harness from the vehicle? I already have the dash off, and the seats out etc.

[TX82FIAT]

Removing the wiring harness is easy. Putting a new wiring harness in its place with proper connections, relays, fuses, grounds is another story. I took the spaghetti wire out of the dash and painstakingly found some hot to ground and continuity issues. I also cleaned connections and grounds replacing some of the older aluminum connections. Finally installed a few relays like the headlight relay with a higher output alternator. No electrical issues in almost eight years with the current car. I do need to remove the cowl and clean the wiper motor again as the wipers have recently started to move slow again. But hey..... the wipers work!

[Tristantinus]

Removing the wiring harness is easy. Putting a new wiring harness in its place with proper connections, relays, fuses, grounds is another story. I took the spaghetti wire out of the dash and painstakingly found some hot to ground and continuity issues. I also cleaned connections and grounds replacing some of the older aluminum connections. Finally installed a few relays like the headlight relay with a higher output alternator. No electrical issues in almost eight years with the current car. I do need to remove the cowl and clean the wiper motor again as the wipers have recently started to move slow again. But hey..... the wipers work!

I dont think im putting a new one in its place, just cleaning the old one and repairing any bad leads

[klweimer]

I don't think you can even buy a new harness these days. With the dash out, you can access the harness pretty easily. I'd check all the grounding points, clean up all the connectors, remove stuff you don't need and call it good. I'd also replace all the instrument lamps.
Kirk

[spider2081]

I dont think im putting a new one in its place, just cleaning the old one and repairing any bad leads

I agree with repairing the harness in place. there is hours of labor removing the harness with out damaging it and anything you can do out of the car can be don in the car.

[Odoyle]

Currently doing this repair to my 77/73, I am using the wiring harness out of my 79 parts car for replacement parts, +1 on buying a DC Power Supply for bench testing. Take LOTS of pictures when removing everything, it really helps.

[Tristantinus]

Looking at the wriring diagrams of the 75 and the 78 there are some differences, does anyone know if i can "update" my 75 to mirror the 78 without issues?