Headlights go off when switch to high beam!!
 

Pretty disconcerting the first time it happened, which was in a dark canyon at the time. Did a search, but only found one thread close and that was for a FC that was stuck in high beam and wouldn't switch out.

To diagnose and try to correct I:

1. Replaced the dash flash switch, no change.

2. Replaced the headlight relay (which the shop manual gives every indication should be the cause), no change.

Anyone heard this one before?

Any suggestions?

this is just a shot in the dark but maby the light blubs are tweakin out?

or maby a short somewhere in the wires?

check all fuses?

The fact the low beams work fine but the high beams don't proves that the fuses, headlight switch, headlight relay and grounds are all fine. The problem will either be the bulbs or the dimmer relay.

High beam's are rarely used, so it would be really odd if the high beams in both headlights are buned out where low beams are working fine.

This is a real stumper.

probably wrong type of headlights, or factory defect?

I'll switch out the headlights and report back. Still skeptical, but more odd things have happened...................................

maybe a bad positive wire going from the relay to the lights themselves.all I can think of Off the top of my head..

Wait, isn't the headlight relay and dimmer relay one and the same?

It's not as strange as you'd think. Don't sit there assuming it can't be the bulbs, go check them.

I take back what I said above too. It can't be the dimmer relay because it's obviously changing from low to high. That just leaves the bulbs.

is it possible that the high beam circuit is shorted out? so when you turn it to highbeams the power gets diverted and never makes it to the headlights. get a volt meter and see if the highbeam circuit at the bulb is reaching 12 volts. if it is not, then tap into the wire and work your way back in the circuit to see if you can get 12 volts anywhere. if you do, there is a short between where you have power and where you dont. if you have a very low reading it might be short to voltage (feeding into another circuit) and it is not enough power to light the bulb. check the obvious first however, like bulbs,fuses, etc.

I take back my question, headlight relay and dimmer relay are clearly different relays.

Further, on checking, the highbeam indicator comes on even though the high beams don't. Since the indicator sources from the same power circuit as the lights themselves, clearly the circuit is getting power. So, strange as it seems, it has to be the headlights themselves.

I'll swap out the light units tomorrow and report.

One high beam maybe, but both at the same time?

Weird!!

No! Short = sparks and/or blown fuse. There is only one headlight fuse, so if the low beams work it can't be that.

Instead of just guessing, look at the wiring diagram to see how the system works. If you understand that then you'll see how none of the suggested failures could leave the low beams working as described.

That's definitely proof it's the bulbs. Just don't ask me to explain how it happened... ;)

Even though it's almost definitely the bulbs in this case, you should always check suspect parts before replacing them. It always amazes me how often people spend money on replacement parts when they think they're needed, without doing quick and free tests first.

It's happened to me. Jumped in my previous car one night and had no headlights. Even though it was unlikely, the bulbs were the second thing I checked after the fuse, because it was easy to do. And whadiya know? :)

Is the plug for the headlight bulb upside down?

I've also had the two high beam filiments go south at the same time.

Use a meter and ohm out the plug to the headlights to see if the filiment is bad.

So the fact that my high beams work sometimes and dont others, and sometimes the lights will go out completly when i switch between the two, say that its the relay?
I have to put my manuel switch on so they alway stay up and then flick the lights on and off again till they come on.

The Headlight relay is the same as the dimmer relay, I had the same problem but replacing relay solved the problem. Check wires, my guess!!

I had a bad swith and that was the problem. You could select high beam and be driving along and then they'd go low beam all by themselves. I'm talking the switch on the cluster, the one you flip with your finger to go to high/low beam.

Could be another thing all together.

I know they had a bad time soldering connections in these cars...lots of brittle stuff breaking off and what not...something could have been knocked loose...

That definitely sounds like a bad headlight switch.

Wrong, they are two different relays performing two different functions.

[QUOTE=NZConvertible]That definitely sounds like a bad headlight switch /QUOTE]

gutted. thats like my 3rd switch. I have my realy stuffed down under the other ones coz it goes sometimes and dosnt other. and it its sitting upright ( how its supposed to ) it dosnt go at all

must be the relay.

Do you know the part number for the headlight switch wiring harness?

Nope sorry, I only have US parts catalogues The LHD and RHD harnesses will most likely be different.

I might be wrong about the switch. The relays are easy to check, see the FSM Body Electrical chapter page 14-46. If either are dodgy they can be replaced with generic 30A automotive relays (as long as you weatherproof them). :)

I have a similar problem at the moment. Suspect it is the hi-lo beam switch. Low beams work fine, but engage hi beams and no lights at all! Pullung the indicator stalk back towards me and the high beams come on, push it forward and they go off. A wiggle of the stalk and the high beams come on.

i have this same problem! low beams are fine but when i click it to highbeam then the headlights just go out.. i just took out my switch and im about to go clean it up a bit which i doubt will actually work.. anyone know where i can get a switch?

Looking for an old thread of mine, saw this and noticed I never reported the conclusion.

It was indeed both headlight units each with burned out high beams but working low beams. Craziest thing I ever saw, but replaced them back in February and not a problem since.

Very strange, but there it is.