36-3580 HD HEADLIGHT HARNESS Questions M1009

[Abbylind]

So since your switching a relay with the headlight switch and not the lights directly that would decrease the current flow ( amperage) through the switch, correct?

Is this also going to decrease the amps through the headlight fuse in the fuse box?

That is correct. you are using a lower amperage switch to control a higher amperage load via the relay.

 

[85CUCVtom]

Ok cool. I got the concept of it now. So would you want to put a lower amp rated fuse in the fuse box then?

 

[Abbylind]

Ok cool. I got the concept of it now. So would you want to put a lower amp rated fuse in the fuse box then?

Technically you could, but remember there are other lights in that circuit, side marker lights, taillights, parking lights. I'd leave it alone...

 

[85CUCVtom]

Kinda forgot about that. I read also that that fuse powers the horn and the courtesy light fuse too.

Just for the heck of it has anybody used their multimeter to read the amperage of that fuse while everything in on. Everything, the headlights, blinkers, foot on the break, horn on, courtesy light on. Everything that the fuse powers.

I'd be curious to see what the amp readings would be before and after the HD harness installation. Maybe ill do it when I do mine.

 

[85CUCVtom]

Oh! Dont forget to fuse the 12v from the battery! An inline thermal fuse or thermal circuit breaker is a must...

What amp rating fuse did you use?

 

[MarcusOReallyus]

Tom, I have not done this yet, but you are probably good with a 20 amp fuse. If that blows, go 30.

If that blows, troubleshoot!

 

[Abbylind]

What he said>>>> If you use a thermal breaker a 20 or 30 amp is fine too

 

[85CUCVtom]

Cool. Thanks. I know I posted earlier in the thread about installing this harness, well I just finally got around to ordering one yesterday.

I'm going to install the harness, snap a few pics for SS, then hopefully in the next month or so install my new to me dash harness/fuse box.

 

[pbrstreetgang]

I installed this setup in my 1009 and for a long time ran the highest rated silverstar lights. A lot of light, so much in fact that people would flash me to switch on my low beams, which is what they were looking at. Problem was i kept popping bulbs, sometimes 1 or 2 a year. i read that this is an issue with those bulbs. saving up for leds.

now i have another issue. my lmc harness keeps blowing relays. i know this because when i reverse them on my harness, the high beams will work, or vice versa. i believe that there is a short in either the existing light harness, or in the switch in the cab. not sure how to figure out which one, as i have never been able to figure out how to access the steering column.

 

[MarcusOReallyus]

I doubt the problem is with the switching side of the circuit. It's usually high current that fries a relay, and the current on the switching side is very small. I'd look on the high current side of those relays first.

Also, it's possible they are just junk relays. I've never ordered from LMC, and I have NO idea what kind of quality goes into those harnesses, but I do know there are a lot of junk relays out there, made in China. If LMC got a batch of those, that might be the whole problem right there.

 

[IdahoPlowboy]

After installing my harness upgrade I dont have bright lights just the dims anybody have a clue whats going on?

 

[85CUCVtom]

After installing my harness upgrade I dont have bright lights just the dims anybody have a clue whats going on?

If it worked before, I would check the high beam relay. Could be bad.

 

[Lifeline]

What gauge wire would you suggest for this harness? I would like to install HID lights as well. How did they work out for you?

 

[MarcusOReallyus]

Would there be any advantage connecting to the negative terminal of the back battery?

That's a great plan, if you want smoke and fire and jello. Well, no jello, but depending on what you do with the rest of the system, you'll either have nothing working or you'll smoke something.

 

[K9Vic]

Would there be any advantage connecting to the negative terminal of the back battery?

That's a great plan, if you want smoke and fire and jello. Well, no jello, but depending on what you do with the rest of the system, you'll either have nothing working or you'll smoke something.

That is 12 volts, the negative terminal of the back battery (Battery #2) is where the 12v 8gauge cable goes to the 12v terminal bock on the driver side firewall. The front battery #1 positive and rear battery #2 negative are both 12v, so connecting to either one is fine. I run my M1031 12v accessories CB, radio amp and accessory plugs off battery #2 negative post. My 12v winch and 12v jumper cable system is run off the front battery #1 positive post. it is perfectly safe to run12v off the rear battery negative post as long as you truck is stock 12/24v hybrid.


The negative post on the second battery of a 24v system is 12v.

 

[MarcusOReallyus]

Yep, you are right. Post in haste, repent in leisure.


Still, if you need more connections and the front batt's positive is getting crowded, I think a better approach is to run off the positive of the front battery to a new buss bar mounted on the fender wall near the batteries. Then there's no cause for confusion, especially if someone not familiar with the system goes poking around in there.

 

[llong66]

You mention "junk China relays", where is a good place to get good quality, made in America relays? Is there a particular brand to look for?

Thanks,
Greg

 

[K9Vic]

Yep, you are right. Post in haste, repent in leisure.


Still, if you need more connections and the front batt's positive is getting crowded, I think a better approach is to run off the positive of the front battery to a new buss bar mounted on the fender wall near the batteries. Then there's no cause for confusion, especially if someone not familiar with the system goes poking around in there.

Correct, this is exactly what I did in my 1984 Suburban CUCV clone. One in the front to distribute to all my accessories and to the rear battery that also has a junction block from the CUCV trucks.

Front



Rear



See these posts for more details, #115 and #127
http://www.steelsoldiers.com/showth...007-or-M1029&p=1477174&viewfull=1#post1477174

http://www.steelsoldiers.com/showth...007-or-M1029&p=1553247&viewfull=1#post1553247

 

[SFC Deal]

Hi Everyone. I called the guys & gals at LMC Truck they told me this would NOT work for a 24 volt truck. Any thoughts?

 

[Warthog]

The headlights are 12v. It will work fine.