Headlight Fuse Issues

[Scamper]

Doc - can't tell you what the problem is without an EWD, but you have most likely found the source of your troubles. This is where the EWD comes in handy...

If you happen to know the PO, you might want to ask the dork why he put that wire there.

 

[Doc]

I wrote him a letter asking why the lights were funky 8 weeks ago, still haven't heard back. Probobly never will.

My thoughts are that the fuesable link blew, and this was the only way they could make the lighting work... perhaps? I don't know. I'm guessing now. It's wierd that that wire was supporting the headlights. No wonder the 'tail' fuse kept blowing out.

 

[Scamper]

Doc - the fusible link supports the entire power grid. If it went, you'd know it.

In looking at my FSM, I see that there is indeed a headlight relay as well as a separate headlight control relay with separate R/L fuses. This is not located in the kick panel, but up front next to the radiator. Don't know if this applies to your tuck, but you FSM may show something similar. I'm thinking that perhaps one of these fuses went, and the guy just tried to bypass it with a wire without fixing the root cause.

At any rate, you need to get the EWD and/or sort thru that customized wiring job. Maybe someone can post that page?

 

[RavenTai]

The following applies to the 96 LX, yours should be same/similar but I don't know for sure

The head light relay is closed when the headlight switch is turned to on, (low’s) it provides battery + to the two headlight fuses, the fuses provide power to all four bulbs but only the lows have a ground and therefore the highs do not light at this point, when the switch is moved to the high or flash position a ground is provided for the high beams directly through the switch

What color wire was it tapped into? Break the system in half, with the switch turned on check for voltage at the 2 headlight fuses, 15A "Head (LH)" and 15A Head (RH)"

If there is no voltage pull out the relay and check for voltage at pins 1 & 3 (schematic printed on relay)

the EFI system is on the same fusible link as the headlights your truck should not run if it were blown, it would not hurt to take a look though (incase there is some other changes made) the fusible links are short wires that come off the + terminal of the battery if it looks like a wire they are OK, if it looks melted or burnt there is trouble, they are replaced as a set and around $8 for the assy. IIRC from or favorite parts guy

 

[RavenTai]

Someone with a 93 EWD please confirm if there are any differences

Headlight Diagram

 

[Beowulf]

>> I see that there is indeed a headlight relay <<

Well that proves my memory is shot. I'll edit the above post so as not to confuse others and remove all evidence of my mistake.

-B-

 

[Safado]

Someone with a 93 EWD please confirm if there are any differences

Headlight Diagram

Try these...

 

[Safado]

Doc, PM me your email if you want the High Res. shots.

 

[RavenTai]

hmm looks liek the 96 has 2 grounds for the lows wile thw 93 has one, looks similar otherwise but there may be other subtle but important diffrences

 

[Safado]

that's all I could see at a quick glance.

 

[Riley]

Yea i thought the groud for both high and low beams was switched. I think that's the case on my 95.

 

[Doc]

Ok, both of the headlight fuses in the engine bay fuse box are intact. I didn't test for power, but will do so tonight, then I'll test the relay as well.

How do I test the relay itself? Put the multi-meter across which posts?

The reason I suspected the fusable link was because in the owners manual it says "if the lights do not work and the fuses are intact check the fuseable links".

 

[RavenTai]

I think it would be easier for you to test the socket and see what the relay is being given, if it is being given everything it needs but not outputting what it is suppose to I would replace it

Test the socket: With the headlight switch to on if you do not have power at the fuses check the relay socket for power at pins 1 & 3 and a ground on pin 4, if you have all of this the relay is suspect

If you want to test it instead of just replacing the suspect relay you could test it by providing 12V across 3 & 4 of the relay to close it (you should hear and feel a click) and then check resistance between pins 1 & 2 it should be very low, less than .5 ohm or so when closed, infinite when open

 

[Doc]

Thanks RavenTai, I'll check the socket tonight with my MM. I hope it's as simple as a bad relay, because winter is coming soon and I'll need those brand new HIR headlights. Right now I have to make do with markers only.

 

[Doc]

OK here we go.

This is the engine bay fuse block:

this is with the "HEAD" relay pulled out, I numbered the slots because I didn't know any other way to describe them.

Alright, position 1 is power, as is position 3. Position 2 is grounded, and Position four is neither of the above.

I used the 12V tester and position 4 did not ever light up, under power or ground, and not with the switch turned on either.

So, please electrical guru's tell me what I do next.

 

[RavenTai]

Did you just arbitrarily number those pins? If so you are lucky as that is their correct pin out.

OK the 1 & 3 have power, this is good, pin 2 is grounding through the bulbs this is normal (unlit bulb is a direct short) pin # 4 should be a ground, this is the pin that leads to the switch and it is not what it should be the relay is not suspect at this point as it is not getting all it requires to operate properly, this does not grantee it is good (likely is good) just that you have other problems preventing it from working weather it is good or bad it cannot work with support from other components

Possible causes:

A bad headlight switch
B bad diode
C bad transistor (light retainer relay)
D bad ground to switch
E bad wiring in-between A-D

Both the diode and “light retainer relay” are hard to get to so next you should get access to the switch and its connector for further troubleshooting,

To test the switch reinstall the head relay and ground pin 13 (black and orange see diagram for pin out) of the headlight switch connector the headlights should come on, if they do then everything up stream is OK, if not post up and we will move on,

If grounding pin 13 works next test the ground by shorting pin 13 to pin 11 (one of the two white & black wires) the headlights should come on, if they do the headlight switch is bad, if they come on when 13 is grounded to bat – but not when to pin 11 the ground for the switch is bad, if they never come on more troubleshooting in needed but you have the problem cornered to in-between the headlight switch and headlight relay there is nothing expensive between the two but it is all hard to get to

If you need headlights for now you could fashion a jumper with spade terminals to short pins 1 and 2 of the relay socket with the relay removed, this will turn on the lows, you will have to remove the jumper every time you park as they will not turn off with ignition, to make the jumper you will need a crimpier or soldering iron some fairly heavy wire (12 gauge or so?) and the matching male spade terminals

 

[RavenTai]

oops just though of another posibility, bad ground to the switch I will edit the above posts to reflect

 

[RavenTai]

when you tested the relay socket did you have the key on? if not retest

 

[Doc]

Yes, I random numbered, and checked the actuall diagram later on I did get lucky!

yes, I tested both with the key on and with no key.

From the EWD that was send by Safado I think Pin's 11 and 13 are in block C-14? But I don't know the location of this block. Under the dash?

 

[RavenTai]

Yep C-14 it is going to be either in the steering column or in the dash near the column, I would start by removing the lower kick panel and see if you can get an eyeball on it, there are 2 connectors on the switch you can identify C-14 from the diagram