Headlight Issues: Rough Drive Home

Classic4X4

Well-known member
1986 D90 LHD 200/300TDI Last night in a rather intense rainstorm, my low beams decided to quit on me. The dash indicator for the headlights began to flicker and I later noticed when getting gas all lights except the low beams worked. Originally I could use the high beams by pushing the switch forward but that function stopped working and I had to tape the high beam lever back to have any sort of lights for the drive home. I tried to bypass the light switch with a bit of wire but again, everything but low beams worked.

to sum it up:

All lights work except low beams

High beams only work when pulling lever toward driver

No fuses are blown

Ground? Relay? Any tips would be greatly appreciated!
 

Red90

Well-known member
Probably the high/low switch has gone. Very common. But, really, you need to personally fault find with a meter. The internet is not a place to solve electrical faults, IMO. Grab a wiring diagram and a meter and locate the source of the fault.
 

NPT90

Well-known member
Probably the high/low switch has gone. Very common. But, really, you need to personally fault find with a meter. The internet is not a place to solve electrical faults, IMO. Grab a wiring diagram and a meter and locate the source of the fault.

Sadly this, could be a lot of things, sounds like the switch is fried, could also be shyte headlamp connectors, fried wire bundles, basically a lot of stuff. Buy a relay harness or add them in so in the future you can avoid shorts or water ingress causing switch failure.
 

Viton

Well-known member
Had the same issue a few years ago, but I had noticed the low beams had become dim (yellowish) in their output in spite of being halogen bulbs. Then BOOM, they went out on the freeway at 70 MPH. My failure was the switch.

IF this is your case, you'll require a new headlamp stalk/switch and one of the following will almost permanently assure it will never happen again.

http://www.ebay.com/itm/2-Headlight...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649
 

Classic4X4

Well-known member
Got it!

Turned out to be the blinker/high low beam lever. Plugged the new one in and all good. Guess while I'm at it ill replace all the other switches I already ordered :D Now just a matter of getting this steering wheel back on without screwing up the alignment I just perfected. Can anyone recommend a good headlight relay harness to avoid future problems? Are they all similar or is there a go-to for the LR guys? Thanks everyone!
 

Bostondave

Well-known member
PO of my truck replaced the headlight switch twice on mine and it still can be finicky at times. It occasionally bounces to the off position when I first turn them on. Never has happed underway. I think my steering wheel is crooked by 1 or 2 splines as well - sounds like it could be the result of swapping out the stalk. I’ll wait until I locate a leather 36 spline wheel to get it perfectly straight.
 

ezzzzzzz

Well-known member
I'd seriously consider using load relays to take the high current off of the new switch. You'll add years to that switch and get brighter headlights to boot.
 

jymmiejamz

Founding Member
Callsign: KN4JHI
The internet is not a place to solve electrical faults, IMO. Grab a wiring diagram and a meter and locate the source of the fault.

Unfortunately, most mechanics barely know how to use a DVOM, let alone an at-home mechanic.
 

Viton

Well-known member
Turned out to be the blinker/high low beam lever. Plugged the new one in and all good. Guess while I'm at it ill replace all the other switches I already ordered :D Now just a matter of getting this steering wheel back on without screwing up the alignment I just perfected. Can anyone recommend a good headlight relay harness to avoid future problems? Are they all similar or is there a go-to for the LR guys? Thanks everyone!

I use this one, easy to install, just needs a hot lead & ground wire.
http://www.ebay.com/itm/2-Headlight...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649
 

Classic4X4

Well-known member
Problem

So I installed the headlight relay harness. essentially there are two relays, one connector goes to each headlight and a third connector connects to the OEM headlight plug. for some reason when I turn on my brights (either by flashing or pushing foreword on the lever) they stay on and will not return to low beams unless I turn the main light switch on and off again. Anyone run into this issue? any suggestions? thanks everyone!
 

NPT90

Well-known member
So I installed the headlight relay harness. essentially there are two relays, one connector goes to each headlight and a third connector connects to the OEM headlight plug. for some reason when I turn on my brights (either by flashing or pushing foreword on the lever) they stay on and will not return to low beams unless I turn the main light switch on and off again. Anyone run into this issue? any suggestions? thanks everyone!

Really shouldnt be possible, you have 2 signal wires coming from the headlight loom (single plug that went into the headlight connector).

You must have a backfeed through the ground somehow? I would pull the relay out of the factory loom, put a meter on the factor headlight connector and see if you have voltage at the high beam headlight connector when the low beams are on. Essentially see if you can mimic the behavior without the relay in place. Aside from that you could try using the other headlight connector to see if it does the same thing.

It is possible that you headlamps were doing something similar before just hard to notice they were partially lit. It doesn't take a lot of voltage to fire the relay.
 

Classic4X4

Well-known member
Been meaning to post an update for a long time. I installed a dual relay for the headlights. They?re definitely brighter and I?m loving it. For some reason when I flash the brights or turn them on they stay on and won?t turn off unless I turn the main headlight switch off then on. Additionally, the bright indicator light is always lit very dimly. Any idea what I screwed up installation wise?
 
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