lmc HD headlight harness gmc/4 lights

[nrb's70gmc]

Hi everyone, i got 4 new h4 style headlights and a lmc hd headlight harness for my 1970 gmc for x mas.

i plugged the lmc 3 prong/male harness into the factory headlight low/high harness/plug nearest battery (as directed)


the factory headlight harness had the 3 prong/female light plugs on the outside low/high then the 2 prong/female high only to the inner lights.

so thats how i ran the HD harness.
I plugged the new h4 headllights in and the inner lights were on (for low) then the outer lights came on for high (opposite of factory) i cant figure out whats wrong. im really confused

---------------------------------on a side note--------------

the h4 lights that came with the new housings are all low/high 3 prong
(my mistake on x mas list)

when i tested the headlights (mentioned above) the inner lights were on low- but the outside lights were a very dim yellow.

when i clicked on high beams the outer lights came on but then the inner lights dimmed to a faint yellow.

i know i need to buy 2 H1 bulbs now.
i just dont know why the 2 prong inner lights came on (low beam)

i disconnected the HD harness and plugged original lights back in and they worked normal. 2 outer low beams on--- 4 on high beam.

[nrb's70gmc]

could i use 2 H7 bulbs for the high beams? (would they fit)?

[DaBigKahuna]

If the inner headlights are set up for H1s, H7s won't fit. The bases are different.

Also, if they are set up got H1s how are they grounding? H1 ground through the base of the bulb so that needs to be grounded to the vehicle.

[nrb's70gmc]

all 4 of the light housings have h4's in them i just need to change 2 bulbs to a single beam (high) i dont know if there is a single beam h4 made or if h7's have the same base. IMO looking at h7 base online, looks very simular to a h4base.

[passthebuck]

I have the LMC headlights in my GMC but I didnt use their harness. I got the headlight plugs at NAPA & I built my harness with relays & thick wire. I set it up so that on low, just the low filament on the outers comes on, but on high, the low filament on the outers go out, the high filament in the outers come on & all four filaments in the inners come on. I figured, why waste the 2nd filaments in the highs?

[DaBigKahuna]

The H7s will not fit in the h4 sockets.

I looked at the LMC catalog and you need a pair of 36-0301 for your high beams. They are the same as the 36-0300 low beams except they have adapters for the wiring harness.

[nrb's70gmc]

ok guys im confused again :/

i have been thinking about this problem
even if my inner lights are a h4 the high beam should work becouse the inner light plugs are two prong.

for testing i only have the D-side lights in and this is what happens when i turn on the lights.

1, turn on lights (low)
2, inner light is on outside light is dim
3, turn on high beam outside light is on high inner light is dim

i dont understand why this is happening
power/ground for the harness are direct from battery the two relays are plugged in

i plugged the hd harness into the 3prong low/high factory light plug (p side)

then ran the new hd harness 3 prongs to the outside lights and 2 prongs to the inner lights.

[nrb's70gmc]

Originally Posted by DaBigKahuna

The H7s will not fit in the h4 sockets.

I looked at the LMC catalog and you need a pair of 36-0301 for your high beams. They are the same as the 36-0300 low beams except they have adapters for the wiring harness.

I dont have the lmc lights i picked up the lights/housings from another source i just bought the lmc harness to use with them.

[nrb's70gmc]

i just went and plugged all four lights in and tested it out(same thing happens)

inside lights on outside lights on but dim
click high beam on (outside lights come on and inner lights dim)

i tried switching relay plugs just to make sure that was not it. the light do the same thing.

[nrb's70gmc]

just double checking things,

i noticed on the lmc HD harness it says to run the 2 prong plug to low beams and the 3 prong to high beams.

[DaBigKahuna]

Originally Posted by nrb's70gmc

ok guys im confused again :/

i have been thinking about this problem
even if my inner lights are a h4 the high beam should work becouse the inner light plugs are two prong.

for testing i only have the D-side lights in and this is what happens when i turn on the lights.

1, turn on lights (low)
2, inner light is on outside light is dim
3, turn on high beam outside light is on high inner light is dim

i dont understand why this is happening
power/ground for the harness are direct from battery the two relays are plugged in

i plugged the hd harness into the 3prong low/high factory light plug (p side)

then ran the new hd harness 3 prongs to the outside lights and 2 prongs to the inner lights.

Ahh I think I know what your problem is!!!!!

You're using the standard 3 prong plug on a two prong bulb. I know on a 3 prong bulb, the ground is the middle post. Find out which one of the other 2 prongs is the high beam one and then swap the middle wire with the other one.

Rick

[nrb's70gmc]

Originally Posted by DaBigKahuna

Ahh I think I know what your problem is!!!!!

You're using the standard 3 prong plug on a two prong bulb. I know on a 3 prong bulb, the ground is the middle post. Find out which one of the other 2 prongs is the high beam one and then swap the middle wire with the other one.

Rick

All 4 of the bulbs are h4's so there all 3 prong bulbs
2 of the light plugs are 3 prong and 2 plugs are 2 prong (like the factory setup)

i figured the 3 prongs were low/high/ground and the 2 prong plugs were high/ground.

i have the lights connected as mentioned above. and yes on the 2 prong connections the low prong is not used. FOUND THIS PICTURE ONLINE

[nrb's70gmc]

i went and checked the wires on the lmc harness and somthings messed up arrording to the pic above.

looking at lmc harness the 3 prong plugs head on from front there are 2 GRRENwires coming out the center post one BLACK from the left and a BROWN wire coming out the right

on the 2 prong plugs from front 1GREENwire left and 1 BLACK wire from right.

i dont know why this lmc harness is wired like that (if wrong)

[nrb's70gmc]

just to make sure for those of you with the lmc harness

does the hd harness plug into driver side or passenger side 3 prong female light socket?

[nrb's70gmc]

here is the light kit that i have http://www.prostreetlighting.com/pro...-5-34-4pc.html

all four bulbs are the superwhite zenon h4 bulbs 65/55 watt

[Indycar1]

It sounds like maybe you have a grounding issue, or your pulling too many amps. Maybe check all your grounding location, or possibly add a relay
Posted via Mobile Device

[nrb's70gmc]

Originally Posted by Indycar1

It sounds like maybe you have a grounding issue, or your pulling too many amps. Maybe check all your grounding location, or possibly add a relay
Posted via Mobile Device

are you talking about a 3rd relay? there are 2 already
i ran the headlight grounds direct to the battery.

believe me this lmc plug and play harness is making me feel stupid more and more :/

[Indycar1]

Lol, electrical issues suck. I re-read some of the posts and missed the fact that you already ran them through relays. What type of relays did u use? Also, you may try and run the ground to the chassis instead of the battery. Theoretically they're the same point, but it may not be making a good connection.
Posted via Mobile Device

[nrb's70gmc]

Originally Posted by Indycar1

Lol, electrical issues suck. I re-read some of the posts and missed the fact that you already ran them through relays. What type of relays did u use? Also, you may try and run the ground to the chassis instead of the battery. Theoretically they're the same point, but it may not be making a good connection.
Posted via Mobile Device

im using the relays that came with the lmc harness i will take note of trying chassis ground however the lights do turn on (if you read some of the first post you can probally understand what my issue is)

[DaBigKahuna]

More and more this is sounding like a ground issue to me.

I might suggest trying each headlight individually (with the other 3 unplugged) to see if it changes. Then I'd get my multimeter and check each plug for proper power on both high and low settings. I'd check for power using both the ground on the plug and then a separate chassis.

[nrb's70gmc]

Just for kicks i unplugged the heavy duty harness and plugged the lights in to the factory light plugs - everything works like normal (of course) there lights not very bright because there powered though the head light switch i also tried switching the grounds to chassis as well with the heavy duty harness with no luck.
Posted via Mobile Device

[nrb's70gmc]

here are the relays that came with the lmc harness
http://www.shori.com.tw/product_detail.asp there are two of them (high/low beam)

[nrb's70gmc]

this is how the stock harness/light plugs are wired- i dont know why im having a problem with the hd harness plugged in-

[DaBigKahuna]

ok NRB... we know that the original truck wiring works. So that is a plus.

If I was sitting in front of that GMC... I'd want to check the plugs of the harness for proper power with a VOM.

Either you are not getting proper power TO the plugs and that would indicate a problem with the relays or you're not getting the power out of the plugs correctly and that would be a ground.

Heck... if you weren't at the other end of the state, I'd drive up there and give a hand. It's gotta be something simple.

[nrb's70gmc]

Originally Posted by DaBigKahuna

ok NRB... we know that the original truck wiring works. So that is a plus.

If I was sitting in front of that GMC... I'd want to check the plugs of the harness for proper power with a VOM.

Either you are not getting proper power TO the plugs and that would indicate a problem with the relays or you're not getting the power out of the plugs correctly and that would be a ground.

Heck... if you weren't at the other end of the state, I'd drive up there and give a hand. It's gotta be something simple.

thanks for the offer and all the help--this harness is driving me nuts
today when i had the harness pluged in i tested it with a test light (on low beam) i was getting power to the outer low beam lights but also the high beam on the inner plugs.