The Stovebolt Site Forums The Shop Area The Electrical Bay Fog light Hook up on 1949 Chevy 3100

Have finally finished all the wire harness installation. Everything works great. Now I am going to work on fog light hook up.
Previous owner had wire from the bat terminal on voltage regulator go to fuse then to #30 post on relay.
Next wire from relay was on post #86 to the switch in cab.
The 2 fog light wires go to the 2 # 87 posts on relay.
The wire that comes from #85 post on relay is the one I don't understand. Appears to have been connected to the terminal block on fender and had another wire spliced to it to go to the other side terminal block. Would it have been connected to the high beam lights on terminal blocks? And is it ok to have this hooked up to the battery terminal on the voltage regulator? Thanks for any information. Grady.

The relay has two separate circuits. 30 is the input feed for the load, 87 is the output to the load. Then there's 85 and 86 to the coil in the relay to pull it in to connect 30 and 87. One pin (85 or 86) needs a powered circuit and the other a ground. You can put the switch on the ground side or the power side.
Here's a diagram of standard 5 pin relays.

If the 2 fog light wires were connected to 87 and 87A, wouldn't only one light work when the switch was turned on?

Yes, both fog light wires need to go on 87. That goes hot when you put power across 30 and 86. If one was on 87A, it would be on when the switch was turned off.
On factory fog light installations, fog lights won't work with the high beams on. So you could supply power to the relay coil from the low beam terminal on the dimmer switch. If you switch to high beams, the fog lights would turn off. I have fog lights on my F250 and did not wire them that way, so I can have fog lights on with high or low beams.

I have been studying and looking at the relay. It shows on the side of relay that when power is across 30 and 86 they both turn on? The 86 wire goes to a switch in cab and other side of switch is grounded. So when I turn on switch it actually completes the circuit buy grounding. Is that correct? And is it OK to have the #30 wire connected to the battery terminal on the voltage regulator? Thanks, Grady.

I should have said it turns on both 87 wires. It's been a long day.

I would guess it's OK to have #30 connected to the voltage regulator battery terminal, but you might want to power them an accessory contact on the ignition switch. If you have it hooked to an unswitched terminal, leaving the fog light switch on would kill the battery eventually if the engine isn't running.
If there are two 87 terminals, those would be energized when the relay is pulled in with your switch. I've never seen a relay with two 87 terminals, but I suppose they exist.

You really need a fuse or a self-resetting circuit breaker as near the power source as possible. For instance, if you decide to get power from the power from the battery terminal of the regulator you should connect the fuse or breaker there, then feed the other side towards relay pin 30.

What Bill said. Always put a fuse at your power source.

There is a fuse between the power source and the 30 terminal. A circuit breaker doesn't sound like a bad idea either. Will get it together tomorrow morning. Thank you all for the help. Grady

Thank you all for the help. They are wired and work as they should. Low beams they're on, high beams they go off. Now for some nice weather so we can take her out. Thanks again, Grady.