Still fighting headlights

[xs-style]

1987 k5 blazer

I'm trying to do the h4 harness upgrade on this thing. I've done it on my 78 with the lmc harness and had no problems. This thing has been a double pain in the arse. Ive tried three harnesses, from two different sources. I've swapped relays. And still my problem remains. All four headlights stay on all the time, regardless of the high beam switch. The highs and lows work fine with standard sealed beam bulbs. It simply won't with with the harness mod. Does anyone have any ideas? Frankly I gave up on this project a month or two ago for the same reason. After another month or so of driving with the sucky sealed beams I'm trying again. Anyone have any ideas that might help me make it work this time around?

[homemade87]

I had problems with my 82 . I got a harness and all was screwy . I cant remember where I got it at ( cheep one ) . I could not get it to work right . As it turns out I had to re pin the plugs on top low high headlight bulbs . My top bulbs are low & high , bottom bulbs are just high . Now on low just the top burn on low and on high all 4 come on .

Its been to long and cant remember all the particulars but I may have had to re pin the main connector that plugs in the oem harness as well . Also on this cheep harness the relays are not the same ,one is a single pole and the other is a dble pole . If you happen to pull them out to look at them and reverse there location it will screw things up as well .

In the end I guess some trucks a different , I do not know why . but the harness I got must have been for a different year truck ( maybe pre 80's ) . The harness you have will work but it sound like you are going to have to do what I did .

I know this may or may not help but it may lead you into a direction to get it to working . Get out the multi meter .

[gmachinz]

If you are running H4s, you need to switch the low and ground terminals in your stock 3-prong headlight connectors-leave the stock high beam wiring the way they are. Quality harnesses arent cheap for even simple upgrades but the inferior ones can be suspect a lot.

[xs-style]

Well something homemade said reminded me of a diagram I had last time. I've attached it here in case we figure this out and someone else has the same issue.

Gmachinez, thanks for that. That is the information I was hoping to see. I didn't know what connectors to repin

[xs-style]

Well I got a new socket, some weatherproof bullet connectors, and proceeded to rewire as per the diagram. ground to the upper, high and low as they should be.

Now I have no lights at all, and (going by my under hood gauges) no fuel pressure. I guess I just need someone to say there's no way these two things could be connected, and to convince me that this supposed upgrade will work someday and be worth this enormous pain in the arse.

[xs-style]

Just looked closer... No interior lights, no cluster lights...

[xs-style]

Double checked again today in the daylight. Wires are right, tight, and grounded.... But I've still got nothing.

Headlights aren't working, no fuel pump kicking on, no courtesy lights, and horn. Checked the fuses and they're fine.

I just don't see how changing one headlight connector could do this. It's gotta be a grounding issue... But where? I changed one headlight connector.

To recap, the previous problem was that the lights were all on, all the time. And the connector was falling apart when I tried the repin, so I switched the connector for a new one.

[BHTH]

Originally Posted by xs-style

Double checked again today in the daylight. Wires are right, tight, and grounded.... But I've still got nothing.

Headlights aren't working, no fuel pump kicking on, no courtesy lights, and horn. Checked the fuses and they're fine.

I just don't see how changing one headlight connector could do this. It's gotta be a grounding issue... But where? I changed one headlight connector.

To recap, the previous problem was that the lights were all on, all the time. And the connector was falling apart when I tried the repin, so I switched the connector for a new one.

For your original wiring light green = high beam, tan = low beam, black = ground. I think you have to switch your leads side to side for the H4. The top conductor is low beam for both. You will know when you hit the dimmer if you are right. If you have lost something else it may be that you have left a black conductor out and have lost your ground. If not, and your fuses are OK, I would look at your fusible link.

[xs-style]

Going by that diagram the top should be the ground on both.

Both black grounds were hooked up.

I dunno what may have gone on. I got another new connector and I'll try again in the morning.

[BHTH]

Originally Posted by xs-style

Going by that diagram the top should be the ground on both.

Both black grounds were hooked up.

I dunno what may have gone on. I got another new connector and I'll try again in the morning.

Black is the ground in this case. I don't buy that 4656 diagram one bit seeing the connector you cut off the truck. Out of curiosity, is the a dual or quad headlight setup?

[xs-style]

It's the four headlight setup

[BHTH]

Originally Posted by xs-style

It's the four headlight setup

The pic of the original connector on the rad support, had you changed the pins on it. Regardless, the colors are what I had said before so you just need make sure they are hitting the h4 on the right terminals.

[xs-style]

That connector hasn't been repined. I replaced it because it was brittle and I thought I might break it trying get the old pins out.

I'm theory, changing the pins should clear up the problem with the dimmer switch not working and all the lights staying on.

What's really got me tripping is what could cause the other issues. With the fuses all being fine, that only leaves a ground problem.

Changing that connector didn't require taking any grounds loose. If I somehow screwed up connecting those four wires into the three of that plug, one would think if have blown a headlight fuse... But I didn't.

[BHTH]

Originally Posted by xs-style

That connector hasn't been repined. I replaced it because it was brittle and I thought I might break it trying get the old pins out.

I'm theory, changing the pins should clear up the problem with the dimmer switch not working and all the lights staying on.

What's really got me tripping is what could cause the other issues. With the fuses all being fine, that only leaves a ground problem.

Changing that connector didn't require taking any grounds loose. If I somehow screwed up connecting those four wires into the three of that plug, one would think if have blown a headlight fuse... But I didn't.

From your original to the H4 I think you just need to swap side to side. The tan should still be on top. As for other things being out and no fuses blown. Battery connections/battery dead or fusible link. Chack bat voltage at your fuse block. I can't see anything you could have done at the connector to cause that.

[BHTH]

The other thing to remember is the low beam has two elements and one will be lit even with the high beams selected.

[SCOTI]

Originally Posted by xs-style

Double checked again today in the daylight. Wires are right, tight, and grounded.... But I've still got nothing.

Headlights aren't working, no fuel pump kicking on, no courtesy lights, and horn. Checked the fuses and they're fine.
I just don't see how changing one headlight connector could do this. It's gotta be a grounding issue... But where? I changed one headlight connector.

To recap, the previous problem was that the lights were all on, all the time. And the connector was falling apart when I tried the repin, so I switched the connector for a new one.

Fusible link gone bad?

[xs-style]

Is the fusable link on an 87 an inline holder for a glass fuse? Do you mean the one down at the starter?

[SCOTI]

Originally Posted by xs-style

Is the fusable link on an 87 an inline holder for a glass fuse? Do you mean the one down at the starter?

Down @ the starter.
I only say it because while messing w/something electrical one time on a car we popped the link.

[xs-style]

Morning update:

Changed out the headlight connector again, no luck.

I changed the style of connector that i was using to put the new headlight plug on. (Went from a weatherproof bullet to a standard spade)

Double double checked the grounds. Didn't move em, so they're still as they were when I bought the truck. And they're tight.

Checked down at the starter for a fusable link... Doesn't seem to have one. Power and grounds are there but anything else is just wiring up in the heat shield tube.

I'm lost. I even called a friend that worked for a gm dealer and wiring and electrical was his primary job in the shop. He's old school. Like back from when these were new trucks till recent retirement. Even bouncing this situation off him... What I've got here shouldn't be able to happen.

[Max1775]

This may sound like a really stupid question, but have you checked the connections at the battery and the main ground?

[SCOTI]

Originally Posted by xs-style

Morning update:

Changed out the headlight connector again, no luck.

I changed the style of connector that i was using to put the new headlight plug on. (Went from a weatherproof bullet to a standard spade)

Double double checked the grounds. Didn't move em, so they're still as they were when I bought the truck. And they're tight.

Checked down at the starter for a fusable link... Doesn't seem to have one. Power and grounds are there but anything else is just wiring up in the heat shield tube.

I'm lost. I even called a friend that worked for a gm dealer and wiring and electrical was his primary job in the shop. He's old school. Like back from when these were new trucks till recent retirement. Even bouncing this situation off him... What I've got here shouldn't be able to happen.

There should be a Fusible link @ the starter.

[Dayton601]

was trying to research it, here is a guy who did his, they are round, but same principle, if not, there are a couple of other videos here that might help trouble shoot,

https://www.youtube.com/watch?v=KvcfSaYTy6g

[xs-style]

Well I was poking around again today. Can anyone tell me what this thing with the disconnected fusible link is?

[gmachinz]

Not sure but it’s not factory that I can tell.

[Dayton601]

Kinda stuff you would find with hidden compartments, or perhaps some home made shaved door handle door popper, I had one of those on my front door bell to the house, or perhaps a speaker