VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt Fog Lights relay

I'm finally thinking about hooking up the fog lights on my '36 Coupe.
Just received a fused-Delco headlight relay from eBay. It should easily handle the needed amperage.

My question is "Where is the best place to hook up the "hot" (or high side") of the relay? Do I have to go all the way back to the battery? Is there a better location that was used in later years? How about the battery connection on the generator?

I believe my '51 had it hooked up to a hot lead on the headlight switch. It then ran over to a foglight switch mounted under the dash.

Sorry Bill... I've reread your post. Is your question -How is the light switch hooked up? I've got my wiring diagram here, and it looks like the hot lead is spliced off of the "B" wire from the voltage regulator to the (-) on the ammeter. I'll send you some pics on messenger...

If you took it back to the battery, it would cause the ammeter to register the fog lamp current as a charging current. The connection that Bruce described would give the correct reading on the ammeter.

Obviously I haven't researched this much and I've never owned a car between 1938 and 1955 so I don't have that reference.

My concern was to NOT connect any additional large load to the light switch (or amp meter) behind the dash. Don't want to burn any of the contacts there. The exception would be attaching the "low" side of the new fog light switch to the ammeter and then to the new relay. I'm sure that the existing circuits/switches can handle that.

Then how do I hook up a "high" side large load to the relay? Obviously it's not an original configuration, but there's got to be a simple way to do this while minimizing the risk. (Reminder: Generator with cutout - no voltage regulator.)

Hook the wire with the load after the cutout, and before it gets to the ammeter. I would probably tap it right at the generator cutout to minimize lead length, and put the relay out there too.

If you need it not to show, then hook it to the other end of the wire coming from the generator. That is probably connected to one side of the ammeter, but it could be the ignition switch or something else.

Don't get on the battery side of the ammeter, because as old216 noted, that would cause the current that the foglights draw to register as "charge".

If your starter motor has the small solenoid on top of the barrel,you could pick up the power(+)from the terminal with the lead from the battery on it.

All good info guys Thanks.
I like what you've all suggested.
I might come back here (in a month or two) and post a follow-up diagram showing what I ended up with.

Thanks Bruce (and others) for the comment about the ammeter. Having the correct reading would be worth any extra effort.
Later-----

Bill, I just installed a 6volt relay in my 32’ Olds for the heater circuit. The Olds ignition switch is built into the coil (coil is dash mounted) and I didn’t want to put any additional amp load through it. Like you, my ignition only closes the relay and I took my high side right off of the feed wire from the starter post to the light switch. Another concern was I didn’t want the chance of the heater fan to be left on as you can’t hear the motor and kill my battery. Now I know, even if the switch is left on, the only time the fan will run is with the ignition on.

Great minds think alike. :-)

Okay, here are my wiring diagrams. I'll share THREE with you.

• One is how NOT to hook up the Fog lights.
• Two is a better way to hook them up.
• Three is a simple wiring diagram of the major leads on my '36 Coupe (Standard)

Lastly -- When I was researching this (ie. wire sizes, fuse sizes, hookups, etc) I ran across a comment that most States have laws saying that FOG lights can NOT be activated when the headlights are on HIGH BEAM. They can only be turned on during LOW BEAM or No headlight action. I have decided to keep my electrical draw minimized by running the new FOG lights off the LOW side of the dimmer switch. That way they can only be turned ON when the switch is in the LOW position -AND- turned ON.

I'm open to any comments or further suggestions. We have a swap meet here in two weeks and I"m going to buy the remainder of the parts that I need for this.


EDIT:
I removed the two fog light diagrams. Wanted to prevent distribution of them until I add adjustments. Just spent two hours in the garage bench-testing and tracing wires in my car. I have come to a different conclusion now. I'll post a new diagram in a couple of days. The more that I look into this, the smarter I get. I'm following the old adage - "Measure twice and cut once." But in this instance, it should be "Diagram twice and hook up once."

I may not be following what you are saying, as I don't see where the battery is in any of those.

Ideally, one would want the fog light load to be on the same side of the ammeter that the generator is. When the car is running, and the generator is keeping up, the generator is the source of current. When the car is not running, the battery becomes the source of current.

If the fog lights are connected to the generator side of the ammeter, any current that they draw is siphoned off first (does not register), and the ammeter reads only the current that is charging the battery. When the engine is off, the foglight current will register as discharge (which it is).

If the fog lights are on the battery side of the ammeter, any current used by the fog lights will register as "charge". You could have charge showing on the ammeter, but actually be discharging the battery. With the engine off, the foglights would be discharging the battery, but not registering on the ammeter.

I'm curious as to why you would not be allowed to run fog lights while using high beam lights? If your highs are on, it's assumed that other cars are not oncoming... so who would care if the fog lights are on as well?

It makes no sense to use fog lights with high beam, as they are a low-cutoff, short-distance light. They won't really do any good, and will just draw extra current from the charging system. A third brush generator and a cutout might be struggling to keep up with just high beams.

It is tough to imagine why it would occur to anyone to outlaw it. I am fairly sure my state (WA, USA) does not have this law, but I have heard of it elsewhere.

Brewster, you can't run with foglights and high beams on in Ontario either. The '08 Sierra I had came with figlights that went off when I switched the lights to high beams. I found the foglights to be basically useless in fog, so didn't order them with the truck you have. My Equinox has foglights that also go off when the high beams are put on. I never use them.

The lights are mounted low for a reason-to be under the fog so using with high beam defeats that purpose. I have them on my 09 Silverado and have probably used them only a couple of times.

I didn't mean to introduce a "new" topic. I thought that everyone knew that fog lights were mounted LOW to go UNDER the fog. So not running them at the same time as HIGH beams just makes sense.

And even on my 2008 Chevy Avalanche, the HIGH beams automatically shifted to LOW beams whenever you turn on the factory-installed fog lights.

What I did find interesting is that various States have individual "laws/or/regulations" dictating that fog lights can NOT be activated while HIGH beams are turned on. I just figured that this was federal jurisdiction.

As well, I knew fog lights are supposed to be used low... I just wondered why bother making a law against the high beam use of them...

Ha ha... I "could" say that that is how government officials stay employed - by making unnecessary laws --- BUT I WON'T since it's not nice to post such things on this forum.

Note: I just erased two of my earlier diagrams. You can read my reasoning HERE.

Sent you a PM Bill.

Where I live, most of the drivers use the "fog lights" constantly and it is not something that i enjoy! It causes a flood of light towards the oncoming driver. Some of the big pickups create such a flood of light that is is dangerous for the oncoming driver. All the modern vehicles I know of will not allow the fog lights to stay on when the high beams are activated.

Same sort of thing here in Australia too.Out here it's illegal to drive with the fog lights on during the hours of daylight,but the coppers never seem to do anything about it and the idiots who do have them on must be blind as bats if they do need them on in daylight.

If they are shining in the eyes of any oncoming cars, they are either not fog lights (maybe driving lights?) or they are so cheap or mis-aimed that they could not possibly function as fog lights.

The upper cutoff of a fog light is much lower than low beam. The whole idea is to light up the lines on the road (or the edge of the road!) without lighting up the fog if front of the driver. If it is shining high enough to annoy oncoming traffic, it is also lighting up fog in front of the driver.