Headlights wont dim or turn off

[nrb's70gmc]

Yes, another headlight question -

quick run down
(i have the HD headlight harness from LMC with newer relays, not chinese ones that came with harness, upgraded headlight housings with removable h4 bulbs. have changed dimmer switch within past year

so im at my friends house go to leave
start truck turn on lights

nothing but running lights and blue halos (powed from side markers wiring)
realized high beams were (supposed to be on)

hit the dimmer low beams pop on
hit dimmer lights go out (great high beams dont work)

drive home turn off lights (everything off except headlights)

pull headlights back on

hit dimmer high beams pop on (great working again)
hit dimmer (now wont dim to low beam)

turn headlights off (high beams stay on) with headlight switch off

all other lights function as they should

disconnected battery (lights off) and came in now typing this

[VetteVet]

Sounds like your high beam relay is stuck on. At first it didn't work and then it stuck on.
When you hit the dimmer switch your dims probable were on but the brights were also and so you couldn't see the dim lights.

The headlight switch no longer powers the lights, it powers the relays through the dimmer switch, so shutting off the headlight switch won't turn off the lights if the relay is stuck.

[nrb's70gmc]

Originally Posted by VetteVet

Sounds like your high beam relay is stuck on. At first it didn't work and then it stuck on.
When you hit the dimmer switch your dims probable were on but the brights were also and so you couldn't see the dim lights.

The headlight switch no longer powers the lights, it powers the relays through the dimmer switch, so shutting off the headlight switch won't turn off the lights if the relay is stuck.

How does the headlights turn on and off with the light switch then?

What your saying makes since however I thought that the HD harness uses the headlight switch still for on/off??

[VetteVet]

Most of the headlight relay harness use relays to send power to the headlights and they use the headlight switch to turn the relays on and off. The headlight switch sends power to the dimmer switch which then switches power between the high beam and low beam relays.

The stock system wiring has small wires to carry power from the battery to the headlight switch then to the dimmer switch and back out to the headlamps. This causes a lot of resistance and voltage loss in all that wiring and the lights aren't as bright as they should be. By using relays we can run power directly to the relays and then to the headlights and use the headlight and dimmer switches to control the relays . The relays only need a fraction of the current that the headlights use to turn on, which means that there is little drain on the current and not much loss in current for the lights.

Here is a picture of a relay and the wiring.
the original wires from the dimmer switch go to terminals 86 on the relays and terminals 85 are grounded. These little coils are all that the headlight and dimmer switch operate. When the coils close the main power wires on terminals 30 and 87 are connected and send full voltage to the headlight terminals.






Here's a diagram of a headlight relay harness showing how the power goes from the battery to the relay and then to the headlight.

[nrb's70gmc]

Originally Posted by VetteVet

Most of the headlight relay harness use relays to send power to the headlights and they use the headlight switch to turn the relays on and off. The headlight switch sends power to the dimmer switch which then switches power between the high beam and low beam relays.

The stock system wiring has small wires to carry power from the battery to the headlight switch then to the dimmer switch and back out to the headlamps. This causes a lot of resistance and voltage loss in all that wiring and the lights aren't as bright as they should be. By using relays we can run power directly to the relays and then to the headlights and use the headlight and dimmer switches to control the relays . The relays only need a fraction of the current that the headlights use to turn on, which means that there is little drain on the current and not much loss in current for the lights.

Here is a picture of a relay and the wiring.
the original wires from the dimmer switch go to terminals 86 on the relays and terminals 85 are grounded. These little coils are all that the headlight and dimmer switch operate. When the coils close the main power wires on terminals 30 and 87 are connected and send full voltage to the headlight terminals.

Attachment 1682942




Here's a diagram of a headlight relay harness showing how the power goes from the battery to the relay and then to the headlight.


Attachment 1682943

Thanks for all that im going to try new relays

[nrb's70gmc]

So baught a new relay and new dimmer switch

pulled the high beam relay and surprise one terminal was crusty and burnt
checked the female side and noticed that the terminal isnt in there anymore (i think)

tested with test light (one wire red/white stripped is hot all the time) then with headlights on black/white striped is hot.
terminal (one that is missing- has 2 brown wires) and the last terminal is brown/white

niether brown or brown/white stripped wires light up (with or without high beams clicked on)

im running higher watt h4s and figured thats why it burned? best way to fix? buy new female end or just new spade end?

[VetteVet]

What I'm gathering from all this is that you are pulling more current than your components can handle. I would look at the Chinese relays and see what their current limits are and compare those with the ones you replaced them with. You should have at least the same capacity. If you do then it is not enough to carry the load of the high beam lights.

For instance if you have 30 amperage relays then you should go up to 40 or more amps. The terminals and plugs are not heavy enough either and you should replace both male and female with heavier duty units.

I would run 12 gauge wires to the lights from the relays if you don't already have them.

I'd like to see the schematic diagram of the harness to better evaluate it's effectiveness.

The controller circuit for the relays is adequate because the relays require a small amount or current to operate. That would be the headlight and dimmer switches and the tan and light green wires to the relays.

Since you have upgraded your headlights you need to match them with the proper components. VV

[nrb's70gmc]

Originally Posted by VetteVet

What I'm gathering from all this is that you are pulling more current than your components can handle. I would look at the Chinese relays and see what their current limits are and compare those with the ones you replaced them with. You should have at least the same capacity. If you do then it is not enough to carry the load of the high beam lights.

For instance if you have 30 amperage relays then you should go up to 40 or more amps. The terminals and plugs are not heavy enough either and you should replace both male and female with heavier duty units.

I would run 12 gauge wires to the lights from the relays if you don't already have them.

I'd like to see the schematic diagram of the harness to better evaluate it's effectiveness.

The controller circuit for the relays is adequate because the relays require a small amount or current to operate. That would be the headlight and dimmer switches and the tan and light green wires to the relays.

Since you have upgraded your headlights you need to match them with the proper components. VV

So taking a look at the headlight bulb (website) that I have. They have two models. 55/60 watt or 90/100watt. ( in the 7000k color) I can't remember wich ones I bought without pulling a bulb.

The Chinese relays are long gone. Can't remember what the rating is but new one does not have a rating on them either. (I remember it took a while to find a 4 pin relay at parts store) that's why I kept the box.)

For now. Only running low beams. (Diffrent relay brand btw) (low beam relay looks brand new)

The reason for two diffrent relays is becouse the parts store only had one of each)
At the time.

I should note the lmc harness for gmc's is wired wrong so my harness has been cut and modified to work right.

Don't have a diagram but I would be suprized If someone on here hasn't posted a lmc harness fix. (For gmc's)

[nrb's70gmc]

FIXED

after trying the parts stores for a 4 pin relay pigtail (with odd faces looking at my relay.)

i just made my own pigtails and high beams work again.