Headlight mystery

[Gary Crutchley]

Guys I have a 65 230SL, occasionally while driving in the daytime I notice that the high beam headlights are on.  A quick flick of the indicator stalk usually rectifies this and I haven’t been too concerned.  However, this morning I noticed the high beam headlights were on while the car was parked in the garage and had been there over night.  The lights were definitely not on when I put the car away after a run yesterday as I gave it the usual clean and would have noticed.  This means that they mysteriously came on by themselves overnight!  Once a gain a quick flick of the indicator stalk turned them off.  Its bit of a worry for me in terms of flat battery and the potential for an electrical fire so before leaving for work I disconnected the battery.

My question is:  Is it likely to be the switch at the steering column or the relay causing the problem?  Many thanks in advance for your help.

[George Des]

There is no relay on our headlight systems if everything is stock. You ma want to check you headlight grounds. My euro version lights were doing all sorts of strange things. I traced it to faulty grounds at the headlight. The ground wires were attached by screws but the small area that is supposed to be bare metal got pained over during restoration.

[Gary Crutchley]

Thanks George - I'll look into this.  Much appreciated.

[garymand]

Hi Gar, Your grounds are fine or the lights wouldn't come on at all.  You have to have +12V applied for the highs to come on.  Your troubleshooting points to the stalk. It sounds physical, maybe a terminal inside has broken loose intermitently making connection.  If a wire is off and touching, I don't think you could get it to turn off so predictably.  the highs should come on flacky when you flick the highs on with the stalk.  I took a look at the diagram, the brights work with the headlight switch off.  The stalk switch goes directly to the high side of one of 2 fuses #9 and 10.  If either fuse is blown only drivers side high comes on.  strange to me.  The stalk applies B+ directly to the back side of #10 fuse.  I do see the dash bright light should be on too.  And the floor switch is between the light switch and the supply  or input side of the 2 fuses. 

Anyway, pull the stalk switch and see what's a miss.