VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt Delco-Remy headlight relay install help

I am interested in installing a pair of original Delco-Remy #1116789 headlight relays in my 1948 Chevy ½ ton truck. It is still a 6V electrical system. I am still using original Guide black-metal backed headlights from the day, and want to continue using them. The lights work, but are dim. I understand that I should use one relay for high beam, and one relay for low beam. I am looking for photos of the wiring runs required for both the high and low beams and/or wiring diagrams, as well as placement of the relays. Any insights are appreciated. I am not an electrician! Thank you.

LUKE

Here is a copy of the Delco installation sheet for that relay, dated 4-10-1940. Diagram on the right shows the wiring recommended for two relays, separately controlling high and low beams. If the diagram is saved to a computer desktop, it should have enough resolution to be legible when zoomed in.

Doug

Thank you for the installation sheet. I understand that modern relays are available at much less expense; I want the old-school look from the Delco relays. From what I have been able to glean, the installation looks to be quite straight-forward. It appears either #10 or #12 wire is acceptable. Is the best placement of the relays side-by-side or stacked on the driver's side inner fender near the front lamp? Any and all insights related to this project are appreciated. Thank you.

From an electrical perspective, the best place to grab power is the "bat" terminal on the regulator, and the best position for the relay is whatever results in the shortest "big" wires. The big wires would be the ones from the "bat" terminal to the relay, and the ones from the relays to the bulbs.

Control wires, the small wires that just trigger the relay coils can be as along as you want.

In practice there are other considerations. I have used many brands of relay on more modern cars back in the 80s to run euro headlights. Some were a very similar type to this Delco relay, and frankly this type of relay in general is pretty unreliable by modern standards. Most problems have to do with water, and you can minimize risk if you are aware. Since they are not sealed, water can get in and ruin them, and fog or frost can get in and cause them to fail to come on, or more likely fail to shut off due to internal icing.

Never mount them with the bakelite side up. Can up and bakelite down is best, but at the very least mount in such a way that water cannot stay inside the can. Find a dry spot. In most vehicles the front side of the core support is very bad, and the back side of the core support is much better. The firewall is better yet. Up high toward the hood is better because of splash.

Finally, before you decide on a spot, get the truck wet, and open the hood to see where the water went. For example, on one of my old installations I had the relays (3 of them) mounted up high on the firewall in available space in-between existing electrical stuff. Later I discovered there was a notch in a pinch weld that turned out to drain rainwater right on top of one of them. They were high grade 12v relays, far better than anything available in-period and correct for 6 volt cars. They were mounted with pins down, so worked pretty well despite the dampness. That one relay though would fail every 2 or 3 years because rainwater was running over the top of it. The other 2 relays that stayed dryer lasted decades.