A Question About LED Headlights and Wiring Harnesses

[SteveW]

Greetings from Southern California !!

I'm familiar with the strategy of rewiring traditional headlights with a "relay" wiring harness such that all current doesn't flow through the
headlight switch and voltage drop is minimized.

If one were to replace our headlights with new technology LED headlights and their lower current draw - would this "relay" harness stIll be beneficial
??

Thanks in advance for your answers and comments. I truly appreciate all of the helpful advice that's shared here.

Steve W
1973 23'
Southern California

 

[steve jess]

If the system was designed without a relay, I don't see why you'd need one in any case. It would just add one more point of failure.

The answer to your question is no, the current draw with LEDs is much less, so a relay would be hard to justify.

Steve Jess - Tucson, AZ
Mid-day/PM newscaster
Arizona Public Media
________________________________
From: Gmclist on behalf of Steve Weinstock
Sent: Tuesday, May 23, 2017 9:25:19 PM
To: gmclist
Subject: [GMCnet] A Question About LED Headlights and Wiring Harnesses

Greetings from Southern California !!

I'm familiar with the strategy of rewiring traditional headlights with a "relay" wiring harness such that all current doesn't flow through the
headlight switch and voltage drop is minimized.

If one were to replace our headlights with new technology LED headlights and their lower current draw - would this "relay" harness stIll be beneficial
??

Thanks in advance for your answers and comments. I truly appreciate all of the helpful advice that's shared here.

Steve W
1973 23'
Southern California

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Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[richshoop]

I would retain the relay. I would also suggest using one wire size larger wire than suggested. Note that LED's are current driven devices, the controller for the LED's will have an easier time of it with clean, minimum voltage dropped, power. Eliminating the relay does eliminate that as a possible failure point, but a properly rated and sized relay should have a lifetime of at least 100,000 cycles, most will do 1 million.
If you eliminate the relay and just run the lights directly through the switch who knows what size wire is used, we are talking about 40 year old vehicles here, what kind of condition the contacts are in, and possibly multiple switches.

BTW checkout www.delcity.net and www.waytekwire.com for wiring supplies

----- Original Message -----

From: "Steve Weinstock"
To: "gmclist"
Sent: Tuesday, May 23, 2017 9:25:19 PM
Subject: [GMCnet] A Question About LED Headlights and Wiring Harnesses

Greetings from Southern California !!

I'm familiar with the strategy of rewiring traditional headlights with a "relay" wiring harness such that all current doesn't flow through the
headlight switch and voltage drop is minimized.

If one were to replace our headlights with new technology LED headlights and their lower current draw - would this "relay" harness stIll be beneficial
??

Thanks in advance for your answers and comments. I truly appreciate all of the helpful advice that's shared here.

Steve W
1973 23'
Southern California

_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[Ken B]

People install relays to reduce the current across the light switch and wiring. The relay coil only draws a minimal amount of current and the relay
switches the higher current for the light(s) over a shorter path. A shorter path means less voltage drop and brighter lights. Since LEDs draw much
less current and most are rated for the same amount of light output at 10 to 30 volts, the benefits of using a relay is reduced or eliminated.

Don't bother installing a relay with LED lights.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[Rdenney]

Even with the regular headlights, the difference is minimal. It's a good
idea to wire in a load-reduction relay for higher-wattage lights (back in
the day when such were available). The standard sealed-beam headlight was
55 watts low beam and 60 watts high beam, as I recall from some deep
memory. Cibie and other companies of yore sold non-DOT-legal "off-road"
(I'm making quote signs in the air) headlights that were rated at 100/110
watts, or something like that. That doubled the current draw which
overtaxed the circuits and the switch, and increased the voltage drop.
Those headlights really needed a load-reduction relay.

I was just looking at the specs for the Grote 90951 LED replacement for a
sealed beam headlight. These are expensive! They don't rate it by wattage,
but the current draw for the high beam is 2.13 amps at the nominal 12
volts--no more than half of conventional sealed-beam bulbs. Also, they work
with 9-32V systems (for compatibility with 24V systems) and so I suspect
they are voltage-regulated in any case. The advantage to LED, it seems to
me, is that they DON'T need all the extra load-management stuff.

Rick "who would be attracted to the Grote replacement were it not nearly a
full GMC cost unit" Denney

> People install relays to reduce the current across the light switch and
> wiring. The relay coil only draws a minimal amount of current and the relay
> switches the higher current for the light(s) over a shorter path. A
> shorter path means less voltage drop and brighter lights. Since LEDs draw
> much
> less current and most are rated for the same amount of light output at 10
> to 30 volts, the benefits of using a relay is reduced or eliminated.
>
> Don't bother installing a relay with LED lights.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com

 

[michael1]

When I first got my GMC, I upgraded from sealed beam headlamps to a replaceable halogen style bulb and added high and low beam relays. About 2 years
ago I upgraded to Trucklite LEDs and left the relays in.

As far as needing them, no you do not need them for LED headlamps.

But should your headlamp switch ever fail, it is not too difficult to hotwire them on at night.

--
1973 GMC 26' Glacier - Unknown Mileage - Has a new switch pitch transmission with Powerdrive

 

[john r. lebetski]

Keep in mind the GM headlight switch is also a self resetting circuit breaker. If you use that signal to trip a relay, you need to put some sort of
appropriate (lower rated) self resetting breaker supplying the switched side of the relay. If you fuse it and the fuse blows you are in the dark. On
the GM setup if there is a short or partial short (bad lamp) the lights will cycle on and off.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[jesse farr]

I had an alternator go out as I was leaving Talladega. Fortunately, I had four LED driving lights with no relay for some of the back roads between Talladega and Attala so I turned off headlights and drove on. The voltmeter was still showing 12 votes when I hit I59 so I drove on to Soddy Daisy, through Chattanooga, with nothing but the LED driving lights and LED instrument panel lights.

While this is not the kind of behavior I would recommend as far as the LEDs they really don't use much juice.

jesse farr
74 canyonlands 26'

Original message
From: "Steve Jess"
To: gmclist;
Dated: 5/24/2017 12:35:30 AM
Subject: Re: [GMCnet] A Question About LED Headlights and Wiring Harnesses

If the system was designed without a relay, I don't see why you'd need one in any case. It would just add one more point of failure.

The answer to your question is no, the current draw with LEDs is much less, so a relay would be hard to justify.

 

[jesse farr]

Oh yeah, tail lights too.

jof

Original message
From: "jesse farr"
To: gmclist;
Dated: 5/24/2017 8:05:34 PM
Subject: A Question About LED Headlights and Wiring Harnesses

I had an alternator go out as I was leaving Talladega. Fortunately, I had four LED driving lights with no relay for some of the back roads between Talladega and Attala so I turned off headlights and drove on. The voltmeter was still showing 12 votes when I hit I59 so I drove on to Soddy Daisy, through Chattanooga, with nothing but the LED driving lights and LED instrument panel lights.

While this is not the kind of behavior I would recommend as far as the LEDs they really don't use much juice.

jesse farr
74 canyonlands 26'