1981 300SD. The headlight switch was hard to turn off yesterday and now it will not turn at all - left or right. Is this fixable or do I need a new headlight switch?

Suppose I must remove the knee plate?

You need a new headlight switch.

I would disconnect the battery first, the feed from the battery to the switch is unfused.

The knee plate comes off to access it.

The knob pulls straight off, then remove the big nut behind the knob.

Reach up under the dash and give the switch body a quarter turn to unlock the ears from the dashboard and pull back then drop the switch down.

The big connector just pulls off the rear with all the wires attached.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Excellent; thanks.

Any chance it can be fixed? Of course it lasted 33 years.

You could try to open it up, but chances are the 33 year old innards have cracked beyond repair.

Too safety critical in my mind to mess with. Both from a road safety perspective as well as an electrical safety perspective, due to the unfused battery voltage being switched.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

OK; thanks.

Jay Bob - it is fixed. When I pulled off the black knob as you suggested and started to remove the nut, the nut was completely loose. So I went ahead and removed the headlight switch anyway. Put the knob back on while holding the switch in my hand and magic the switch turned in all directions. Reinstalled it and tightened the retaining nut and I have lights again.

Thanks about the advice to twist it to remove it from the panel.

Working again and saved about $100.