Headlight Problems,....Electrical Gurus please help...!!!!

[70Cruza]

How do.....

Im into this like way into it......1994 FZJ80 ABS

after some parts replacements, some testing, and more testing I think I have narrowed down where the problem lies.------****Looking for a

ffirmation there***

Let me say ahead of time that, while trouble shooting, I have found that someone was in this stuff before. The dimmer switch I do not believe was original Toyota part, wires were all tested on and some spliced into. SO i am scared that there is previous problems.and repairs as well.

Now just WHAT to do about it????

Posted this like a week ago in another thread...

I was driving to work yesterday and had my high beams on, Both lights went out at the same time. Running lights, braked, till all OK. I tried my low beams they ALSO were out. I limped back to the house by pulling back on the lever which DOES turn on BOTH sets of lights high/low pass/flash. After searching quite a bit I figured it was probably the "stalk" Switch so I decided to take it apart and see what it looks like.....My thoughts were to clean the contacts as I have read others have done with luck.

SO I have a new stalk, new dimmer switch installed. ALL TESTED GOOD per manual. Main Headlight relay also tested good.

At the Headlight retainer relay I tested the plug and found that I only have 9.5 volts at pin#7 where I should have constant 12V ALL else tested good there.

Now pin #7 from the retainer relay Goes on a red & blue to the Diode then to a red & white to a connector in the dash?? then red & white to the connector in the driver fender, then on a red and green to the #4 pin of the Main Headlight relay. This path is the path that shows abnormal voltage of 9.5.

I JUMPERED from the red/blue @ pin 7 of the retainer relay with a piece of wire with the retainer relay bypassed to the #4 pin of the main relay. LIGHTS WORKED PERFECT. SO it would appear to me that somewhere in that path from pin 7 of the retainer relay to pin 4 of the main headlight relay there is a problem........

ALSO noteworthy from pin #7 to Pin #4 Shows continuity one way +/- and none the other -/+ as it shoud with a diode in the circuit.


So I am wondering what is the cause of the abnormal voltage?? Short somewhere in the wire??


AND where is the harness in the dash??? Sounds like I will be having to find it soon...

Please any knowledge or tips would be appreciated. I took detailed pics all along this process and will be making a complete post of it for others faced with similar issues in the future....

 

[70Cruza]

 

[70Cruza]

 

[70Cruza]

can anyone tell me exactly where that Diode is located??

 

[blkprj80]

On the page to the right of the one you pictured, it will say that D7 is on page xx.
Go to page xx and it will have a picture showing where D7 is. On my 96, it's up and to right behind instrument cluster.

I wouldn't suspect that diode. But I might suspect the Light Retainer Relay assembly, L1 in the diagram. My diagram shows it up and behind the interior fuse panel somewhere. However, that relay assy mainly turns off the headlights if you leave them on and shut off the key (I think).

Go toward the back of your EWD and look for a page that says "headlight" in the corner. Mine is on sheet 3 in section K. Yours is probably different, but you're looking for the Overall Electrical Wiring Diagram pages. Same stuff but presented in a different format.

I would wire a switch between the "bottom" side of that headlight relay coil (pin 4) and use the switch to pull that to ground. That should allow you to drive it hopefully without losing lights.

 

[70Cruza]

I checked the retainer relay. It cheked out ok. Plus I bypassed it completely and still had same problem. NO headlights but running/tail and pass to flash......

 

[Pin_Head]

There is a lot of verbiage that does not clearly state what the problem is, but if the problem goes away when you bypass the diode by runing a jumper wire between pin 4 of the head relay and pin 7 of the light retainer relay, they it is reasonable to assume that the problem is either the diode or the wires in between.

What the voltage is that you would expect on pin 7 may depend on whether the lights are on or not and how close 9.5 is to approximately 12V. You are measuring on the ground side of the relay pull in coil which has some resistance, so you could expect a voltage drop on an energized circuit, but not if you disconnect the plug and then measure.

 

[70Cruza]

Hello and thanks...Yeah sorry for the terminology
the light retainer relay is unplugged and I am measuring at the pin 7#.....

The part above that says service hints shows there should be constant 12v @ pin #7 to ground???

If that wire is grounded out somewhere,.......would that explain the voltage drop to 9.5??

Not looking forward to openeing the dash, but im already in it this far....

 

[70Cruza]

I also plugged the retainer relay back in, and then bypassed only the diode by going from the red/blue off of #7 to #4 and everything worked perfect

 

[70Cruza]

I think I might start at the harness in the fender and work my way back and look at all the wires to make sure that side is good, BEFORE opening up the dash

 

[blkprj80]

I'm interested to hear what you find. Please follow up when you learn more.

 

[Pin_Head]

It sounds like the diode is bad and it may be shorted, accounting for the low voltage. Sometimes it is easier to just run a new wire with a new diode than finding the old one.

 

[70Cruza]

The "Smoking Gun!" as someone else said in a thread I recently read........

Twas a broken wire at the factory splice, which is about 8" off the fire wall.......

There seems to have been problems on this circuit before as several of the wires had been cut into & tested on. .....plus the dimmer switch itself that I replaced,... I don't think was a toyota part, n showed sign on burning on the ground wire. ...


The diode tested good. I will be writing everything up to be an absolute complete headlight thread.....I would hope, since I have been through out most of the wiring, equipment & circuit...


Anyways just wanted to update. The .. is tasting extra good tonight!!!!!! Uhuh.

 

[70Cruza]

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