The headlights on my newly revived '92 240 will not switch from low beams to high beams. The high beam indicator does not light up.

Tonight I noticed that if the engine is not running, toggling the dip switch causes the high beams to come on (flash to pass funstion works). The indicator on the dash also lights up.

In both cases, the position the main light switch does not matter.

I swapped a known working dip relay (behind the left headlight) and it did not make any difference.

I looked at the wiring diagram in the Bentley manual, but can't relate the inset diagram of the headlight switch/relays to the main diagram. Does anyone have a better wiring diagram for the headlights ?

Any other ideas on troubleshooting ?

Thanks

Greg

After replacing the dip beam relay, the headlight relay (safely located in the middle of the dash) and the turn signal switch, I noticed that the screw holding the ground wire on the steering column, located just forward of the TS switch, had fallen out. Reconnecting the wire fixed the high beams.

As long as I'm this far along, I'm going to replace the burned out dash lights and add a voltmeter.

Thanks for the suggestions and wiring diagrams.

Greg

Check the grounds in the engine compartment, especially the left front fender and engine grounds.

The fact that the lights work at all may eliminate device or wiring issues.

Our '90 744 TI would stall when I turned on the high beams - the problem was related to the grounds for the ignition system.

The headlights were stealing the ground connection from the ignition - yours might be doing the opposite.

It is in the FAQ!

I know that your car is not a 700/900, but many items in the FAQ may be of use because of common designs of those and your model.

Items that are mounted in plastic will have ground wires, like lights - metal items get their ground through their mounting to the body or engine,

To avoid future problems, clean any grounds you find and clean and apply dielectric grease to any connectors that you can.

When I did my connectors, I did one a week so that if I had a problem, I knew where to look.

Problems are rarely with "replaceable parts" compared with "cleanable connections."
--
Art Benstein near Baltimore

Will tungsten carbide float on mercury? http://www.youtube.com/watch?v=rFrxY4ug9I0

Thank you Art.