1987 Chevrolet Monte Carlo - replace the wiring harness?

just have general questions

Ask and you shall recieve.

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my headlights and signals only work from time to time and i was thinking it was a wiring issue so i wanted to know if it was a good idea to just go head and replace the whole wiring harness and what harness should i get also i wanna go digital dash

I am thinking it is more likely a switch issue.

I doubt you want to pay for that, assuming that you can actually GET a wiring harness for this 34 year old car.

Spend some time searching the internet to see if such a harness and dash assembly exist. If they don’t, you’ll either have to build one yourself or find a cu$tom $hop who can in$tall the digital da$h for you. Expect to pay lots of money for that work $$$$$$.


Might be an ss. Maybe it’s summer only? Stores it in barn? Mice?

Replacing the harness is a last resort, there are lots of things to check first. Have you gone through every circuit that’s having a problem and checked it out?

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i have not im new at this

Odds are the problems are related to switches; not a faulty harness. I would be very surprised if a harness even exists after this many years. Any harness lying around in a dealer parts room was likely gotten rid of decades ago either as part of a bulk sale or scrapped.

As for a digital dash (and harness) that is going to be a time consuming and expensive thing to do along with being technically deep. An analog harness will be different than a digital harness so that leads back to what do you want to do. Having to pay someone to do this would be obscenely expensive and it might be impossible to find someone willing to even touch it.
If I were to be asked to delve into something like this I would flat refuse and I have replaced some wire harnesses over the years.

i would think its a loose connection or wire being it happens occasionally. switch can be faulty and have loose connection inside. i have had that problem.do you notice it happens more when you go over bumps?

Generally replacing the “computer” or the entire wiring harness is a last ditch, can’t think of anything else, option.

Here’s the very first thing you do . . .

Get yourself the factory wiring diagram for the exterior lighting

Otherwise you’ll be making expensive guesses which probably won’t even fix the problem

db460’s comment about factory wiring diagrams jostled a few brain cells. I have some old service manuals packed away in the attic. I seem to remember there are 2 factory electrical manuals for Monte Carlos and El Caminos of that era. Had forgotten all about them and seems they are in great condition from my fuzzy memory.

Give me a few hours and I will cut the boxes open and see what’s what. If there is an applicable manual maybe I can provide some info or work out something where I can just mail it to you for postage due and the manual free of charge. Back later with a definite answer.


I found the manual and it’s for a 1988 Monte Carlo. Should work as I doubt there is a gnat’s eyelash worth of difference between an 87 and an 88. It’s a GM publication in soft cover. Things are laid out in a current flow format; sometimes called a ladder diagram, and it also has trouble shooting text. Makes it much easier to read and sort out things. The book appears to be new. No dog ears, no smudges or fingerprints, etc at all.

If you can use it and want it provide a mailing address and I will put it in the mail for you and also cover the postage.

The elderly gentleman I got this manual (and a dozen others) from had health issues and moved to town so as to be closer to the hospitals. Sadly, he sold his 2 toys before moving. A 1951 Plymouth sedan that looked near new and best of all; a 1952 fire engine red Hudson Hornet.
I’m going to keep the 1930s Terraplane manual. Never know when one might roll around… :slight_smile: