SL/R129: Turn signal started to come on and stay lit after the car is parked
Thread Starter
Senior Member
Joined: Nov 2010
Posts: 382
Likes: 27
From: Norway
350 SL, R230 - 300 SL, R129 - 1964 Corvette Sting Ray Sport Coupe - Porsche 911 Twin Turbo (sold)
Turn signal started to come on and stay lit after the car is parked
Tonight after i parked the car the turn signal lamps stay on after the car is stopped and locked on my 1992 Mercedes 300 SL, R129
I noticed this after about 30 minutes that the right side turn signal lamp front and rear was lit
I took the car for a short test drive and used both the left, right turn signal and warning signal as well and all worked as it was supposed to do.
So i parked the car again and went back in to my house
After a while a looked out the window and sure the right side turn signal front and rear was lit again.
Back out again and started the car and the turn signal went out again.
Opened the hood and checked the fuses and could not see anything wrong but after this the right side turn signal stopped flashing and would just stay lit when ii put the turn signal lever to the right.
So i just took out the fuse for the turn signal and i will check it tomorrow.
Any of my fellow member here on the forum have any idea what cause this?
Is the turn signal relay starting to go bad? If so where is the relay located?
I noticed this after about 30 minutes that the right side turn signal lamp front and rear was lit
I took the car for a short test drive and used both the left, right turn signal and warning signal as well and all worked as it was supposed to do.
So i parked the car again and went back in to my house
After a while a looked out the window and sure the right side turn signal front and rear was lit again.
Back out again and started the car and the turn signal went out again.
Opened the hood and checked the fuses and could not see anything wrong but after this the right side turn signal stopped flashing and would just stay lit when ii put the turn signal lever to the right.
So i just took out the fuse for the turn signal and i will check it tomorrow.
Any of my fellow member here on the forum have any idea what cause this?
Is the turn signal relay starting to go bad? If so where is the relay located?
Junior Member
Joined: Apr 2015
Posts: 17
Likes: 1
1993 Mercedes 300 SL
I have a 93 300SL, and this is just a thought. Do you get a warning lamp on the bezel when this happens? Try working the light switch thru all positions a few times. That helps clean off the contacts. I replaced mine, and it was a very easy task. The Lamp Control Relay is in the black box right behind the main fuse box, drivers side back corner. Those relays can sometimes stick. I have a problem with the right rear tail/brake light sometimes not working. With the car running, I open the hood, and use the back of a heavy screwdriver and tap the top of the relay box. Then I check the dash and see if the warning light has gone out. Lamp Control Relays are difficult to find. Hope this sheds some light on what you are seeing.
Thread Starter
Senior Member
Joined: Nov 2010
Posts: 382
Likes: 27
From: Norway
350 SL, R230 - 300 SL, R129 - 1964 Corvette Sting Ray Sport Coupe - Porsche 911 Twin Turbo (sold)
Thanks for the advice akula 10 
When it comes to electric switches i usually take them apart and clean them 
I bought a Blazer ZR2 where the switches for the mirror adjustment, the switch for the 2WD - 4WD - 4WD Hi - 4WD Low - Auto 4 WD and the remote key fob did not work and i just took them apart and cleaned them using electro clean on q tips and they all started to work like i had replaced them with brand new switches
I know that a lot of people replaces the battery in their key fobs even if they replaced the batteries a week ago thinking that the batteries are the problem when the problem often it is a dirty key fob. Just open it and clean the contact points on the solder card on the key fob
But i have already fixed the problem on my SL (or it works as it is supposed to at the moment)
What i did was to have a look at the fuses and they did not look like new to say it like this so i took my Dremel with a little brass wire brush on and cleaned some of the contacts in the fuse box (top and bottom of the fuse contact points) and also cleaned the fuses and everything works like a dream
Just to be on the safe side i replaced 43 of the fuses even if i had cleaned them
The fuses have aluminum "strips" on them which often gets very dirty/corroded.
I have looked for copper fuses up here in northern Europe but no copper fuses to get hold of up here
Since i think copper fuses are much better than the aluminum ones, i must have to order them from the US since the US is the only place i have seen the copper fuses for sale
When it comes to electric switches i usually take them apart and clean them I bought a Blazer ZR2 where the switches for the mirror adjustment, the switch for the 2WD - 4WD - 4WD Hi - 4WD Low - Auto 4 WD and the remote key fob did not work and i just took them apart and cleaned them using electro clean on q tips and they all started to work like i had replaced them with brand new switches
I know that a lot of people replaces the battery in their key fobs even if they replaced the batteries a week ago thinking that the batteries are the problem when the problem often it is a dirty key fob. Just open it and clean the contact points on the solder card on the key fob
But i have already fixed the problem on my SL
(or it works as it is supposed to at the moment) What i did was to have a look at the fuses and they did not look like new to say it like this so i took my Dremel with a little brass wire brush on and cleaned some of the contacts in the fuse box (top and bottom of the fuse contact points) and also cleaned the fuses and everything works like a dream
Just to be on the safe side i replaced 43 of the fuses even if i had cleaned them
The fuses have aluminum "strips" on them which often gets very dirty/corroded.
I have looked for copper fuses up here in northern Europe but no copper fuses to get hold of up here
Since i think copper fuses are much better than the aluminum ones, i must have to order them from the US since the US is the only place i have seen the copper fuses for sale
Last edited by TheSaint; Mar 2, 2020 at 09:45 AM.
