Tail lights and dashboard lights

[w113abudhabi]

Hello all

I hope someone can provide some guidance which may help to speed up the resolution of an electrical issue. My 1970 280SL has recently experienced a problem whereby the dashboard lights and tail lights no longer illuminate. The front headlights and side markers do illuminate when the headlights are switched on. I have removed fuse 7 from the fuse box in the engine bay bulkhead, cleaned it, refitted, replaced it etc with no resolution. No recent work has been done to the car. Any suggestions of where and how to narrow this down please? Unfortunately we have just 2-3 weeks left of nice evening time weather to enjoy driving the car here in Abu Dhabi before it gets tucked away for the extreme summer months. It is already too hot on most days to drive during the daytime so lighting is a game changer right now.

Many thanks

Pierre

[kampala]

Pierre,

If I recall correctly, the tail lights maybe on two fuses (left & right).  So if BOTH tail lights are not working and Dash Lights not working and the fuses are good, I would consider that your LIGHT SWTICH  - position one  - is not functioning.  As I recall, position one turns on both taillights and the dash.     I think the tech manual may have details on to how pull this switch. 

[JamesL]

Would the side-lights (front) be similarly affected? And the shifter light (assuming it's auto) if it's the switch in position 1?

Pierre
Try the "parking" lights or clearance lights as they are sometimes called. Turn the light switch the "wrong" way (anti clockwise) one click and see what lights up front and back. Turn a second click and check again. If you have the rear lights working on either/both of those you have ruled out any fuse issue. If you have one or both, then I reckon your issue can be narrowed down to the switch... The parking lights are so rarely used .

[Tyler S]

Fuses 7 and 8 are left and right. They are tied together between the input side of the fuses and the headlight switch, pin 58. Pin 30 of the headlight switch is bat + input fed off of fuse 1.
Since your headlights work, you know you are getting power to the headlight switch. Your issue lies within the switch, or the wiring from pin 58 of the headlight switch to fuses 7 and 8 of the fuse block.
Start by checking for power at pin 58 of the switch with lights on. If you have power, check the wiring. If no power, the switch is at fault.

[w113abudhabi]

Many thanks to Kampala, James and Tyler for the responses.

I guess to undertake the power tests on the switch I will first need to remove the tachometer and subsequently the headlight switch?

[Tyler S]

You can access the switch by removing the cardboard under dash panel, then remove the headlight switch knob. Unscrew the chrome retaining nut. You can then push the switch back into the dash and swing it down to an accessible position. DISCONNECT The Battery First! Then reconnect when you are sure the switch is clear of any metal parts under the dash. 

[w113abudhabi]

Thanks again Tyler

[ja17]

Before opening up a big job, do the simple checks. Use a 12 volt test light to check your system. Check to see if power is going back to the tail light housing plug. Sometimes just the tail light housing is bad or tarnished. Dash light failure is a common problem as the dash rheostat switch goes bad. You can easily by-pass the rheostat to restore the dash lights.

[Jordan]

Pierre, you said you removed and cleaned fuse 7.  Was the fuse blown?  When I had this issue I had a short in the wiring in the trunk (within the cloth wrapped section) and it would cause fuse 7 to blow resulting in no tail lights or dash lights, while my headlights continued to work.  Obviously if your fuse 7 is OK the problem lies elsewhere, as others have suggested.