Boxster 986 - No high beams, really strange symptoms.
 

Ok, this is a strange one. Last night both of my high beams stopped working at the same time. No high beam light on the dashboard using the high beam selector, pushing either forward or backward on the stalk. I thought it would either be a fuse or a bulb and that if either side stopped working the other side must be disabled too. So this morning I checked the fuses, both are fine. So I pulled the headlight units and tested the bulbs. All OK (tested with multi meter and with a 12v source, they lit up). This is where it gets really strange:

- With both headlamp units removed from the car the high beam indicator light on the dashboard lights up when I use the high beam selector stalk.
- I tested the female connector socket for the headlamp unit and confirmed there is 12v both sides with the headlamp units removed from the car when the high beam control is activated.
- As soon as I refit either headlamp unit to the car there is no longer 12v to the other side connector socket when high beams are activated. The fitted headlamp high beam does not work either.

I really don't get this! Anybody have any idea what to check next? Fuses all OK, bulbs OK and the switches seem to be OK.

Thanks in advance, Paul

Hello Paul,

what kind of headlamps do you have? OEM, OEM Litronic or after market? (Wiring of Litronic is a bit different).

In general this can be a mass problem. Check wiring harness and connectors for a mass (ground) problem. Mass wiring is drawn from left side to right side in LHD cars.

This can also be a headlamp switch problem. Please use forum search function.

Regards, Markus

Hi.

It's a RHD with OEM headlamps. I did try searching the forum but can't find any symptoms the same as mine. There does seem to be voltage at both connectors when the headlamp units are removed and the high beam stalk is activated so I assumed the headlamp switch must work OK?

Thanks, Paul

Not necessarily. You can have a failing switch and still get voltage with no load.

Start by removing the switch and cleaning the internal contacts. To do this, spray contact cleaner inside the switch and switch it back and forth.
Another possibility is the ignition switch. Cheap and easy to replace.

Thanks – I'll try cleaning the headlamp switch next and see if that helps. I didn't realise that there could still be voltage at the connectors when there is no load with a faulty switch.

Hello Paul,

ROW cars do have a different wiring than US/Canada cars. So i think your car is a ROW RHD. Is your car prior MY 2000 or a later model? Wiring diagrams for MY 1999 and prior ROW cars are different.

Regards, Markus

Hi Markus. It's a 2002 ROW RHD. I'm just about to try cleaning the headlamp switch as suggested by particlewave.

Hi Markus.

It's a 2002 ROW RHD car. I can confirm I'm getting voltage at both connectors when under no load.

Thanks, Paul

It's worth checking out your ignition switch. When it fails it makes the accessories in the car do some very strange things.

Thanks Randall. I've ordered the switch and will try that when it arrives. This is super confusing! I really don't understand why there is voltage under no load when I pull back on the high beam flash but nothing when I connect the headlamp or a test bulb.

I have seen one four stalk column switch where the high beam stalk malfunctioned. Everything else was good. These electronic gremlins are a PITA. Keep us posted,

Hello Paul,

i've checked the wiring diagram. I don't think this is caused by the normal headlamp switch in the left of the dash.

If there would be a ground problem this would also affect turn signal and fog lights.

Both headlamps have individual fuses. Sicherung A1 (high beam left) and Sicherung A2 (high beam right). These fuses get their currency via a Terminal 56a. (BS 5/1). If there is a connection problem this would affect both high beam headlamps.

Have you checked the connections and cables high beam switch behind the steering wheel? Any modifications in that area?

The high beam lever can be pushed and pulled. Have you tested both ways?

Have you tested if there is currency running if you push or pull the lever?

Regards from Germany
Markus

Also might want to consider pulling the headlight assemblies out and look at the conditionof the internal wiring. Lots of folks (me included) had found the wiring insulation flake of the wires and short together.

Hi Markus,

I have tried both pulling and pushing the high beam lever. With both headlamp units removed from the car the high beam dashboard light illuminates and I can also measure 12v at both headlamp connector terminals for the high beams. It's only when I refit either of the headlamp units that the dashboard light no longer illuminates when I push or pull the lever and neither high beam works.

I have ordered a replacement headlamp dashboard switch but don't see how that will help with the high beams - the low beams, fog lights, parking lights and turn signal lights all work.

Thanks, Paul

Hello Paul,

i think we need a test scenario.

You've said you have a Multimeter, so you can test different things.

1.)
Remove both fuses for high beam lamps.
Turn headlamps and highbeam on (with installed headlamps)
Check if you have electrical voltage against ground in the fuse sockets.

If yes, the problem lies between fuse socket and headlamp.

But i would say you will have electrical voltage there.

Turn everything off.

2.)
Put in the fuses.
Check if you electrical voltage against ground before and after the high beam lever. To do that you have to remove some parts to get to the connector of the high beam lever / turn signal switch.

If there is no electrical voltage behind the lever but before, than there is a problem with the lever / turn signal switch.

If there is no electrical voltage before the lever we have to check the normal light switch.

The turn signal / high beam switch and normal light switch are connected via point 22. But that would mean, low beams also shouldn't work if there would be a problem with the normal light switch.

Turn everything off.

3.)
To test if you get output from the normal light switch you have to check if you get a signal from the KL56 / K30 2.5 WT/BK cable.

To do that you have to remove the light switch.

But i think the problem is the turn / high beam switch or a failed connection in the connector or something like that. Everything else wouldn't make sense.

If you like i can send you a wiring diagram via email. Just pn me you email-address.

Hope that helps.

Regards, Markus

The failure of the headlight switch can be caused by pitting and carbon buildup on the contacts (they can also just fall apart).
This causes high resistance/low current flow through the contacts, meaning that you can get 12V at the other end, but it is very low current. Apply a load and the contacts cannot supply enough current to power the load. A multimeter has very low load, which is why you are getting a voltage reading with it.

The switches can be cleaned easily as I noted above. Go pick up a $5 can of contact cleaner and give it a try.

It's going to be either the headlight or ignition switch (don't forget to check the wiring inside the headlight as suggested). ;)

Thanks. I'm dropping the car off tomorrow for Variocam tensioner pads so will buy some contact cleaner and try cleaning the switch when I get the car back from the garage.

So, just to clarify, you mean to try cleaning the circular headlamp switch in the dashboard (not the stalk control)? I did check the wiring in the headlights themselves, all looks good. I actually tried applying 12v directly to the various headlight terminals/pins themselves when out of the car and all lamps worked correctly. I used a wiring diagram you posted a while back to identify the correct pins so thanks for that!

The really confusing thing is that the full beam dashboard light illuminates when the headlamp units are both out of the car and I push or pull the stalk control...

Hello Paul,

sent you a PM. particlewaves answer might also be right. But concerning the wiring diagram in that case we should also have a low beam problem. So i would do the check as mentioned above.

Regards, Markus

I've actually run into this twice before and both times the issue turned out to be the switch. Looking at the wiring diagram, it doesn't make sense, but it is what it is.
In the first case, I was sure that it had to be the dimmer switch (high beam stalk) based on the wiring diagram, but it wasn't.

Anyhow, cleaning the switch is cheap and easy, as is the ignition switch, which is why I suggest those first before really digging into the car.
If the switch doesn't solve it, I'd check out the high beam stalk next.

No joy cleaning the headlamp switch with contact cleaner this morning. I've ordered a replacement headlamp switch and an ignition switch so will try those when they arrive.

Out of interest, when the high beams are on are the low beams also on at the same time? Still trying to fathom out how all this works!