I have this weird situation with the electrical system on my 1965 Old F-85.

I can be driving along on the highway or a local city street and the entire electrical system will shut down, the engine will stop running and everything just quits. Sometimes this will last only a few seconds and then everything will come right back on. Other times the car can sit for an hour or so and then it will come back and act like nothing’s wrong. It’s just weird and very inconvenient. Do you have any suggestions?

R.M..

We’ve run into this before on one of our Chevelles. It took some investigation and head scratching before we finally figured this out. Likely your Olds is suffering from the same problem. The issue is 12-volt power comes from the bus bar on the horn relay that is hooked to the battery. This power lead then enters the fuse box on the driver side of the firewall. The fuse box uses thin metal blades that make the connections between the outer and inner portions of the fuse box. The box really isn’t designed to be disassembled although it is made of two pieces.

Over decades of use, the power lead that enters the firewall side of the fuse box has corroded where it makes the connection to feed power to the rest of the fuse box. If you disassemble the fuse box and find the main power lead where it connects to the rest of the fuse box, this is where the problem lies. Over the years, corrosion will cause this connection to disconnect itself from the rest of the fuse box. This will shut down the car’s entire electrical system as you’ve experienced.

The good news is that if you disassemble the fuse box, look for the main power input connector along with the opposite connection on the fuse box side. They should be easy to spot and will probably look funky with corrosion that may or may not be evident. Either way, cleaning these connectors should solve the problem.

Of course, this corrosion will also exist on every one of the electrical connectors in the fuse box. You could spend the time to clean each one and then coat them with something that will slow down the corrosion, but more than likely the damage has been done and no amount of cleaning will eliminate this situation from reoccurring.

grille and Headlights on a vintage chevelle
We re-wired our El Camino to add relays to the headlight circuit and drastically improved the brightness of the headlights on both the dim and bright circuits. (Image/Jeff Smith)

A better move, although more expensive, would be to replace the entire wiring harness with an aftermarket version. There are several companies that offer replacement harnesses. I looked up American Autowire and they will reproduce a 1965 Olds F-85 harness but they need your original fuse box in order to do so. The other option is to order what American calls its Classic Update harness which is a generic harness offering a more modern fuse box using ATC fuses and more circuits that you can add for custom electrical items like air conditioning or other accessories. Painless Performance also offers similar custom harnesses that will fit your chassis with similar options.

There are other companies offering harnesses including M&H Electrical Fabricators. This company will produce an exact duplicate of your existing harness if you desire the car to remain as original as possible. They build harnesses on demand so it may be several weeks or months before the harness can be delivered since they build it to your specific vehicle.

Individual harnesses like the front or rear electrical or the engine harness are also available separately.

Headlight Relay Mod

One thing you might consider is converting your headlight system over to use electrical relays to power up the headlights. The factory headlight circuit runs from the battery, up through the fuse box, then to the headlight switch and then back to the headlights. This lengthy process causes a serious loss of voltage by the time the voltage reaches the headlights. By using relays, you use the headlight switch to trigger the relays that pull power directly from the battery. This offers more voltage to the headlights.

Here’s an In-Depth Walkthrough of the Headlight Relay Mod.

We did this conversion recently on our 1965 El Camino and the headlights went from 11.1 volts to 12.2 with the engine off just running off battery power. While it may seem a minor improvement, this is really a major increase in voltage which makes the headlights much brighter. American Autowire, Painless, and others offer this sort of headlight relay kit or you can make your own conversion using a pair of relays and some intelligent wiring.          

Keywords
Ask Away!, electrical troubleshooting, Oldsmobile
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Author: Jeff Smith

Jeff Smith has had a passion for cars since he began working at his grandfather's gas station at the age 10. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves as a regular contributor to OnAllCylinders.