Posted By: 37 GC Relays - Tue Apr 26 2022 12:41 AM
planning the rewiring of the '37. I'm going 12v with halogen reflectors which I understand should have relays and am in need of advice. Should the relays be wired in #1 between the fusebox and lightswitch #2 between the lightswitch and dimmer or #3 between the dimmer and the headlights requiring two (high and low beams). Also thoughts on the need for a horn relay.
Posted By: Jon G Re: Relays - Tue Apr 26 2022 11:43 PM
Horn relay is a simple answer. You must have one. The horn switch isn't designed to handle the amperage the horn needs by itself.

Headlight relays are a little more complex. You probably do need a relay (2 actually) with halogen reflector lights, but you need to think about it carefully. The way your truck is wired now, the headlight switch has a resetting circuit breaker built into it. That means should any short occur in your headlight circuit you won't blow a fuse (which is a one-time affair) but will allow your headlights to continue to work (intermittently) if there is trouble. You must continue with that scheme.

Here is how one fellow did it:

You'll need 2 Bosch style relays (heavy duty--30 amp). Instead of using 20 amp fuses as he did, I would use one 40 amp resetting circuit breaker (split to the input side of each relay). but otherwise his circuit looks pretty ok to me. Important note: in his drawing, the yellow wire (stock low beam wire) is the wire controlling the low beam coming from your headlight switch and the high beam wire is the one coming from your high beam foot switch. Good luck.
Posted By: 37 GC Re: Relays - Wed Apr 27 2022 07:32 PM
thanks Jon for the drawing. In essence you are saying #3 from my post with 30amp relays and 40 amp breaker. The old 6v deteriorated wiring I tore out showed no signs of a horn relay and was wired direct. possible on a '37? No fusebox of any kind and the only fuse was built into the amp gauge. Horn switch is just a ground through a heavy s wire under the button to a bearing ring in the steering column. rubber holding the button also serves as the spring. I will use a relay there also.
Posted By: Jon G Re: Relays - Wed Apr 27 2022 09:43 PM
Hi Larry,
I think there is a relay on top of the generator going to the horn. One appears in the wiring diagram (below).

Yes, #3 on your post with 30 amp relays and a 40 amp resetting breaker. You may find both the low beam wire and the high beam wire come from your high beam switch. I believe this is the case and the wiring diagram shows this. Many were wired that way, so I'd expect it to be so. Good luck.

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Posted By: Hotrod Lincoln Re: Relays - Wed Apr 27 2022 11:03 PM
Jon, the relay you're seeing on the schematic is the cutout relay for the 3-brush generator that prevents the battery from discharging through the generator with the engine stopped. It's just being used as a junction block to provide voltage to the horn, which operates only when the button at the steering wheel is grounded. There is no horn relay in that circuit. The upper right of that schematic illustrates the optional 2-unit regulator that includes a cutout relay and a voltage regulator. No current control with that system.
Posted By: Jon G Re: Relays - Thu Apr 28 2022 02:19 AM
You're right, Jerry. Seems a good amount of current to run through a horn button, though.
Posted By: Hotrod Lincoln Re: Relays - Thu Apr 28 2022 02:33 AM
6 volt systems are wired to take it. Much heavier gauge conductors, and beefy switch contacts. Then the train drivers and bean counters got into the mix and started making stuff that would just barely last through the warranty- - - -most of the time!
Posted By: Jon G Re: Relays - Thu Apr 28 2022 11:00 PM
Yep, but you know the last 4 6v vehicles I owned all had horn relays and a person gets used to some things...a 1951 Ford Victoria, a 1955 T-Bird, a 1951 GMC pickup and of course the 1952 Chevy pickup. The T-Bird had twin horns (hi/low).
Posted By: jameschevypu50 Re: Relays - Mon Jul 18 2022 12:44 PM
[img][/img]If I may join in here. I purchased a double louder pair of horns for my 3100 years ago. It is powered directly to the battery +. If the battery- wire isn't good and secure the horn is sketchy. I have noticed that when sounding the horn the voltmeter certainly shows a discharge.

I have a 3 wire spade relay for the horn to install. I didn't see a wiring diagram or description of the hook up. On the side of the relay I see #1 then a switch a #3, then the resistance off of that and a #2. Embossed on the connection side with the wire spades I see #1, #5, & #3.

Any clarification on the wiring will be greatly appreciated.

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Posted By: Phak1 Re: Relays - Mon Jul 18 2022 01:02 PM
I think you have basically the same relay as me. Here is a picture of mine that I labeled for clarity. (1) H is horn, (3) 12v is battery (in your case 6v) and (5) S is switch (horn button).

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Posted By: Bill Hanlon Re: Relays - Mon Jul 18 2022 03:38 PM
If JamesChevyPU50 does still have a 6 volt system, that 12v relay may not pull in.

Original wiring ran from hot through the horn and up to the horn button on the steering wheel which provided ground when mashed.

When using a relay, the preferred way (by me anyway) is to run hot to your terminal #3, horn button to your terminal #2 and connect the horn(s) to terminal #1. The other terminal on (each) horn needs to be grounded.

And if it were me, I'd put a fuse or self resetting circuit breaker into the hot line as close to the battery as practical. Mine connects to the battery cable at the stomp starter switch.

Self resetting breakers are cheap and can be found at FLAPS.

Circuit Breaker []
Posted By: Phak1 Re: Relays - Mon Jul 18 2022 11:37 PM
Originally Posted by Bill Hanlon
If JamesChevyPU50 does still have a 6 volt system, that 12v relay may not pull in.
That particular relay sold by Classic Parts, will work on either 6 or 12 volts. The diagrams on both relays (mine and the OP’s) were the same, so I showed him how I wired it up.

I agree it should be fused and I did install a fuse between the battery and the relay.
Posted By: jameschevypu50 Re: Relays - Tue Jul 19 2022 05:23 PM
Thank you all for your concise answers. I really appreciate that.
Posted By: jameschevypu50 Re: Relays - Tue Jul 19 2022 10:20 PM
Relay is in. How about a fuse aamperage recommendation for these 2 horns?

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Posted By: Bill Hanlon Re: Relays - Wed Jul 20 2022 12:14 AM
I just looked at '57 Chevy car, '57 GMC truck and '61 Pontiac car wiring diagrams. None had protection for the horn circuit. I still think it is a good idea.

I just measured the current draw on my horns. About 8 amps for both combined. They are plastic high and low tone horns bought in blister packs at FLAPS. I'd use a 15 amp fuse.
Posted By: jameschevypu50 Re: Relays - Wed Jul 20 2022 12:38 PM
At the moment I used the highest amperage fuse that I have. That is a 20A fuse.
Posted By: fixite7 Re: Relays - Fri Jul 22 2022 06:53 PM
Jon G Think i'll just stay with 2 6014 headlamps that just shine on the white line on dim since I don't aim to drive 85 mph at night in a 50 mph truck. Also want people i'm meeting to be able to see to get by !!
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