Headlight problems

[Rick Norwood]

Well now I am completely stumped. I replaced the Relay with an aftermarket Replacement for $8.00 USD (the dealership wanted $45). This morning when I started the truck, the headlights took about 5 - 10 seconds to light up.

If I have to admit it, I have replaced the Photocell sensor in the dash and the relay for a total of $22. but I don't think I'm anywhere closer to fixing the real problem than when I started.

Two Questions for you electrical experts. 1, can these relays be installed backwards? The pins allow them to be installed into the socket either direction. 2, can the relays be tested?

[mike2004tct]

Originally Posted by Rick Norwood

Two Questions for you electrical experts. 1, can these relays be installed backwards? The pins allow them to be installed into the socket either direction. 2, can the relays be tested?

Does the relay have any markings at all defining the pins and power supply voltage?

Relays would be something like this assuming 4/5 pins- numbers are for explaination as they could be anything, but you get the idea;
pin 1 = coil supply pin
pin 2 = coil ground pin (neutral)
pin 3 = contact 1 common pin
pin 4 = contact 1 normally open pin
pin 5 = contact 1 normall closed pin ( if it's a 2 pole single throw relay)
additional contacts would be numbered similar to 3,4,& 5.


1-----O-----2

3------| |----4
3------|/|----5

1. If installed backwards, most likely you're applying power to the contacts instead of the coil. If the relay is a Normally open contact type, you'd have no headlights. If it's a normally closed contact, you'd be shorting 12 volts (or 5 volts- depending on the supply voltage) to ground, and the relay would probably pop.

2. Yes. If you can determine which 2 contacts are the coil, apply 12 volts (or 5 volts depending on the supply voltage) and ground to those contacts, and listen for a click as you apply power to the coil.
Better yet, if you have aligator clips to apply the power, hook up the ground to the neutral side of the coil, put 1 hand on the relay case, and apply power to the other side (pin) of the coil. You should be able to feel the contact activation at power-up.

[Rick Norwood]

I am almost 100% convinced that I am dealing with a bad ground. I have tried 3 different relays in this socket and all 3 did the exact same thing.

Here is the funny part that I cannot explain. Why do the headlights come on and stay on when I lightly tap on the relay? They do not turn off until I turn the engine off. It doesn't matter if I tap on the relay again and again, drive over bumps etc. the lights stay on until I turn the key off.

From Mike's post, I gather that the relay itself is grounded through the socket, but the relay socket panel sits in a plastic box. So, either the relay (and/or the relay socket panel) has a groundwire going out through one of the harnesses or is somehow grounded through the 3 bolts and fender mounted bracket. All I know is that a light tap to the relay turns the lights on if they don't come on when the engine is started.

[mike2004tct]

Originally Posted by Rick Norwood

I am almost 100% convinced that I am dealing with a bad ground. I have tried 3 different relays in this socket and all 3 did the exact same thing.

Here is the funny part that I cannot explain. Why do the headlights come on and stay on when I lightly tap on the relay? .

My next guess would be a faulty crimp on the socket contact(s). Perhaps corrosion, or weak/broken wires at the crimp.
I'm guessing, but I'd lean towards the socket end being bad, as the wires most likely rum from the socket to the EEM where they'd be grounded internally of the EEM. Tapping the relay would indicate your problem lies right at that point. The base is plastic or phenolic, so no ground would be made through the mtg screws.

I'd also guess this is a hard one to diagnose, as those contacts are buried on the bottom side of the socket, and nearly impossible to see.
If you have some electronic spray/cleaner (similar to WD40, but for electronic contact cleaning), give that a try. I used this stuff on my starter when I was having problems with it last year due to salt spray in the winter. No problems since.

[Rick Norwood]

Originally Posted by mike2004tct

My next guess would be a faulty crimp on the socket contact(s). Perhaps corrosion, or weak/broken wires at the crimp.
I'm guessing, but I'd lean towards the socket end being bad, as the wires most likely rum from the socket to the EEM where they'd be grounded internally of the EEM. Tapping the relay would indicate your problem lies right at that point. The base is plastic or phenolic, so no ground would be made through the mtg screws.

I'd also guess this is a hard one to diagnose, as those contacts are buried on the bottom side of the socket, and nearly impossible to see.
If you have some electronic spray/cleaner (similar to WD40, but for electronic contact cleaning), give that a try. I used this stuff on my starter when I was having problems with it last year due to salt spray in the winter. No problems since.

As a matter of fact I do have some electric contact cleaner. I was thinking along the exact same line, a dirty socket. I planned on blowing out the socket with my air hose, but maybe I'll try both.

[Rick Norwood]

O.K. here we are again or maybe I should say still. The electrical contact cleaner and air hose did not help. I am reasonably sure now that I have a loose wire or connection somewhere in the under side of the Fuse/Relay panel that is mounted to the driver's side wheel well inside of the engine compartment. The panel appears to sit inside of a plastic box. My problem is, I can't seem to find a way to get to the underneath side of the relay panel where the connections are.

Anyone have any ideas how to get inside of the panel?

[CSierra]

You are not alone...I also own a 2000 GMC Jimmy the exception is that the lights come on when I start the truck BUT as you drive it the lights switch from low lights to highlights as you tap along any small bumps in the road. When it switches to the highlights you end up with NO lights at all. This little problem makes for intresting night time driving. Sometimes the lights are totally fine and you can get from point A to B with zero incident. Other time the entire time you are driving it feel like your in a disco club with strobing lights. HELP!!!! Anyone have an answer to this riddle?

[Rick Norwood]

Originally Posted by CSierra

You are not alone...I also own a 2000 GMC Jimmy the exception is that the lights come on when I start the truck BUT as you drive it the lights switch from low lights to highlights as you tap along any small bumps in the road. When it switches to the highlights you end up with NO lights at all. This little problem makes for intresting night time driving. Sometimes the lights are totally fine and you can get from point A to B with zero incident. Other time the entire time you are driving it feel like your in a disco club with strobing lights. HELP!!!! Anyone have an answer to this riddle?

Here is all I have been able to come up with. The large Fuse/Relay Panel that sits on the driver's fender wall has sockets that the prongs of the various relays and fuses push down into. The only thing that makes any sense is that the female clips inside of these sockets are either burnt, corroded, or have simply lost their pinch, resulting in a bad contact between the prong on the relay and the socket. I say this because the slightest tap on the headlamp relay turns the headlights on when they don't come on automatically.

I have tried spraying contact cleaner into these sockets as well as crimping the wires goinging into the connectors on the underneath side of the panel. The contact cleaner seemed to help a little, but nothing so far has fixed the problem.

I was thinking about flattening a piece of solid copper wire into 4 thin strips, bending them into an "L" shape and inserting these copper strips into the 4 socket holes in the panel, then installing the headlamp relay into the socket along side of the copper strips to see if this might make a better contact, but I haven't had the time as yet.

[Rick Norwood]

Well here we are still or again or whatever. Over a year now and I still am stumped. I had a long repreve (8 months or so) with no issues. But the beast has reared its ugly head again. Once again, I sporadically have no head lights and almost always will turn on instantly when I lightly tap on the Headlamp Relay. Once they Headlights do come on, they stay on until I turn off the ignition with the key.

But the other day when this was happening, I noticed something else which seems to me to be significant. I drove around for quite a while during daylight hours and noticed that the headlights would not turn on even when the photocell was covered up or in the shade. So when I got home, I opened the hood and removed the cover to the Fuse/Relay box and found that the Headlamp Relay was HOT. I don't mean warm, it was hot to the touch, and thumping the relay didn't turn the lights on. I swapped the Headlamp Relay with the Relay for the rear windshield defogger and the headlights came on instantly. I switched them back and put the hot one (which had cooled) back in and the head lights again came on instantly again. I had previously checked and re-crimped all of the wire connectors going to the Headlamp relay, so I'm hoping someone might have seen this issue and can steer me in the right direction.

[MT-2500]

Rick
If relay heating up it has a over load on that circuit.
It might be a good idea to get a amp meter on the headlight circuits and watch for any heavy amp draws.

Also wiggle wires around when checking it.

[Rick Norwood]

This is sounding more like a crummy movie with a possible good ending. I found something kinda funny. On the left side of the dash panel, just below the air vent is a little mini panel with the head light switch on it. Just below the switch is a button marked Dome Override. If you push that button twice, the headlights will go out, push it twice more and the head lights come back on. I pushed this button a couple of weeks ago when my head lights were winking out, the head lights came on and they haven't acted up since.

Any thoughts? I am not foolish enough to get my hopes up, but I will keep my fingers crossed.

[Rick Norwood]

AND SO IT ENDS! THANKS TO OLD MASTER, WHO IS A MAN ABOVE MEN, AND HAS THE PATIENCE OF A SAINT. THE PROBLEM IS SOLVED.

After Pouring over the schematics and spending a week exchanging e-mails, Old Master (from 2000 miles away) and I, fixed the problem.

The culprit was a burnt wire terminal in the underside of the Fuse Block that sits on the fender well above the driver's front tire. This Wire was a ground wire dedicated and exclusive to the headlight circuit. It cost nothing to fix. All I had to do was sand the burnt clip clean with a piece of Sand paper and re-attached the clip.

Amen - And I can't even think about how I can ever re-pay OM for his help and guidance.

[old_master]

Awww shucks, twas nothin' Thanks for the kind words, glad I could help. All I did was tell you what wire had a problem. You tracked it down like a blood hound and found it, good job!

Reading through the thread, you mentioned pushing the dome override button twice and the lights went out, twice again and they came back on...... normal operation, Rick. When you start the vehicle and put it in gear, the Daytime Running Lights, (DRL's) automatically turn on the high beam filaments at a reduced voltage. Pushing the dome override twice shuts them off, (should be accompanied with a "ding" from the door chime) twice again turns them back on. If you push it just once, the dome lights will not come on when you open a door.

[Rick Norwood]

Originally Posted by old_master

All I did was tell you what wire had a problem.

Naw, OM you are too humble.

You not only told me what wire had a problem,

You sent me the schematic.

You told me that is was a Yellow wire,

Specifically, a Yellow Ground wire,

And the terminal number it was connected to,

You told me where to look for it, and how to fix it.

All from 2000 miles away.

It took a while to get there, but once I did, BINGO, it was just like you said.

So from now on guys, if Old Master tells you the Moon is made of Green Cheese, just go get the Rye Bread and the Mustard and enjoy the lunch!

Thanks Again Old Master for all your help and guidance.

[plumber31]

Hi I'm having the exact same problems with my 2000 blazer. I was wondering if you could let me in on the secret too haha. Thanks in advanced