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Registered
'90 R129 300SL-24, 94 C140 CL500, '92 W140 400SE,'98 W210 E300TD
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30 Posts
Discussion Starter #1
Hi Guys,
Wonder if anyone's got any ideas on this one, on my '90 300SL-24. I't more an annoyance than a problem, but here goes:

I noticed today my boot (trunk) light had been disconnected, so I reconnected it and it came one.

So, as a check, I operated the micro switch on the latch, but the light stayed on, even after waiting a minute or so. I then tested the micro switch with my multimeter; no problem, switch working fine. Then lock the car with either the IR remote control or key (with trunk latch in shut position to mimmick lid being shut) and the light goes out.....unlock the car and it comes on again.

From what I understand, the light is controled by having it's ground connection shut off, however this isn't happening unless the car is locked. I also tried disconnecting the PSE (central locking) pump, but it didn't make any difference. I'm thinking there may be a sticking relay somewhere that may be causing this.:confused:

Any ideas would be greatly appreciated,

Thanks,
Mark.
 

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Greek God of the R129
SL500-500SEL-190E
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8,391 Posts
Hi Guys,
Wonder if anyone's got any ideas on this one, on my '90 300SL-24. I't more an annoyance than a problem, but here goes:

I noticed today my boot (trunk) light had been disconnected, so I reconnected it and it came one.

So, as a check, I operated the micro switch on the latch, but the light stayed on, even after waiting a minute or so. I then tested the micro switch with my multimeter; no problem, switch working fine. Then lock the car with either the IR remote control or key (with trunk latch in shut position to mimmick lid being shut) and the light goes out.....unlock the car and it comes on again.

From what I understand, the light is controled by having it's ground connection shut off, however this isn't happening unless the car is locked. I also tried disconnecting the PSE (central locking) pump, but it didn't make any difference. I'm thinking there may be a sticking relay somewhere that may be causing this.:confused:

Any ideas would be greatly appreciated,

Thanks,
Mark.
The light is fine.
You have a yellow lever to turn it off manually when the lid is up.
Enjoy the car.
Regards.
aam.
 

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Registered
'90 R129 300SL-24, 94 C140 CL500, '92 W140 400SE,'98 W210 E300TD
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30 Posts
Discussion Starter #4
Hi,
Thanks for the replies. I've already tried the yellow switch on the latch, which operates the micro switch, however it makes no difference to the light, which stays on whatever.

I've also closed the lid and watched through the left light cluster (bulb carrier removed on inside so you can see the light) and it still stays on, until the car is locked. So basically, as long as the car is unlocked, the boot lamp stays on.

I'm going to try swapping the latch from a friend's SL280 R129 later today, just to totally eliminate that.

Mark.
 

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2001 SL500
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1,127 Posts
did you do anything to the wiring. The light comes on when it is grounded. if you taped in to the ground wire or it is picking up a ground from somewhere it will stay on.
 

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Registered
'90 R129 300SL-24, 94 C140 CL500, '92 W140 400SE,'98 W210 E300TD
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30 Posts
Discussion Starter #6
did you do anything to the wiring. The light comes on when it is grounded. if you taped in to the ground wire or it is picking up a ground from somewhere it will stay on.
Hi there,
No I haven't done anything with the wiring, although there was a wire spliced to the ground wire of the lamp, from an aftermarket alarm system that was once installed. It didn't lead anywhere so I removed it, and besides it didn't make any difference to the operataion of the lamp itself.

You're right though, it's defo picking up a ground connection from somewhere, so hoping someone has a wiring diragram to show where that grounding wire goes (it's the purple/green one from memory).

Thanks,
Mark.
 

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Registered
1999 SL500, 1993 S600
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1 Posts
locked boot on my SL500, Aug 1999 manufacture

So, the battery is flat.
Make sure the car is unlocked with the remote.
I take out the battery and SHUT the boot lid.
Now I can't open the lid.
Any ideas as to how I can open the boot lid???
 

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Banned
Y2K SL500 Silver
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8,660 Posts
So, the battery is flat.
Make sure the car is unlocked with the remote.
I take out the battery and SHUT the boot lid.
Now I can't open the lid.
Any ideas as to how I can open the boot lid???
Yes, you can manually insert your door/ignition key into the trunk/boot lid lock and turn to pop open.
 

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Registered
500SL 1992
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46 Posts
Hi there,
No I haven't done anything with the wiring, although there was a wire spliced to the ground wire of the lamp, from an aftermarket alarm system that was once installed. It didn't lead anywhere so I removed it, and besides it didn't make any difference to the operataion of the lamp itself.

You're right though, it's defo picking up a ground connection from somewhere, so hoping someone has a wiring diragram to show where that grounding wire goes (it's the purple/green one from memory).

Thanks,
Mark.
Hi Mark!
Have you fixed your problem? I have exactly the same problem with my trunk light. I will appreciate with helping getting it fixed.
 

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2013 C300 4Matic, 98 SL500 SP1 Pano, 2014 CLA-250 4Matic
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292 Posts
I had the same issue with my 98. Kept killing the battery. It turned out to be the lower trunk latch assembly was missing a spring and also appeared to have a small plastic tab missing that allowed the light to stay on after closing.

If that is your issue please make sure that you properly engage the actuating rod when you replace the lower mechanism or you will be locked out of the trunk.
 

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Registered
1996 SL500, 2000 E430
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3,775 Posts
Heh Let my tale of woe be a lesson to you. Can't emphasize enough to test - before slamming that trunk lid, use your thumb to "lock" the latch - then try to open it with a key.

Of all the repairs I have done to this car, this was the most unnecessary (and dumbest)

Your problem is most likely the plastic switch assembly on the trunk latch has failed.
 

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R129 HTT Founder Member
040 96' SL500, 368 08' E550 4Matic, 775 08' R350 4Matic, 9147 13' Sprinter 2500
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7,523 Posts
Call me crazy but it looks like the picture in post #9 by Rostman it's not the interior trunk light rather it looks like one of the license plate bulbs is out. Rostman stupid question but have you checked the bulb?
 

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Registered
500SL 1992
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46 Posts
I have checked the microswitch. I believe that's the first thing that must works well. I have pressed it manualy and it doesn't any difference. In my opinion latch mechanism is pushing this microswitch to show that the trunk is closed.
I'm pretty sure that is the trunk light. Firstly i was thinking the same this is license plate light but when i had a look closer it appears to be trunk light.
So it doesn't go out even if you press microswitch with the you finger. It must be something else.
 

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Greek God of the R129
SL500-500SEL-190E
Joined
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8,391 Posts
I have checked the microswitch. I believe that's the first thing that must works well. I have pressed it manualy and it doesn't any difference. In my opinion latch mechanism is pushing this microswitch to show that the trunk is closed.
I'm pretty sure that is the trunk light. Firstly i was thinking the same this is license plate light but when i had a look closer it appears to be trunk light.
So it doesn't go out even if you press microswitch with the you finger. It must be something else.

1.Disconnect the switch connector, is the light off?

2.Does the switch click?

3.If you push/pull on the switch, and nothing happens.

4.Check if something is holding it...

5.If nothing changes, replace it.

Regards,
aam.
 

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Registered
500SL 1992
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46 Posts
1.Disconnect the switch connector, is the light off?

2.Does the switch click?

3.If you push/pull on the switch, and nothing happens.

4.Check if something is holding it...

5.If nothing changes, replace it.

Regards,
aam.
Yes it's clicking. When it's pushed trunk light looks starts shining a little bit dimly. I will try to disconnect the switch. Lets see if it does any difference. Thanks
 

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Registered
1997 SL 500 w/Pano, 1999 CLK 320
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601 Posts
The owner's manual says you can set the light to come on...or not...when you open the trunk. It says to use your key in a slot.
There is a white plastic switch assembly on mine, it 's broken, but there is enough left to manually turn it off.

Since you can't confirm whether or not it goes off, I've simply turned it off.
 

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Registered
500SL 1992
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46 Posts
The owner's manual says you can set the light to come on...or not...when you open the trunk. It says to use your key in a slot.
There is a white plastic switch assembly on mine, it 's broken, but there is enough left to manually turn it off.

Since you can't confirm whether or not it goes off, I've simply turned it off.
This switch is pushing microswitch what i was pushing allready manualy so believe it will not make any sense.
 

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Greek God of the R129
SL500-500SEL-190E
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8,391 Posts
My Russian friend.
This is simple.

Trunk open, light ON.
One wire power through the switch bulb, to the ground.

Trunk close,
The latch pushes a spring.
The spring pushes, turns the light OFF.

That is if the fixture is not molested.

What I mean, you can have a separate line to an alarm.
Or you want to remote the light from a different place.
(That will mean more wires.....)???

That's why I asked to remove the connector.
Most likely, you have a stuck slide spring.

Should go, either tic, or tac.

Fast together... tictac. Haha. ;)

Regards,
aam.
 

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Registered
500SL 1992
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46 Posts
My Russian friend.
This is simple.

Trunk open, light ON.
One wire power through the switch bulb, to the ground.

Trunk close,
The latch pushes a spring.
The spring pushes, turns the light OFF.

That is if the fixture is not molested.

What I mean, you can have a separate line to an alarm.
Or you want to remote the light from a different place.
(That will mean more wires.....)???

That's why I asked to remove the connector.
Most likely, you have a stuck slide spring.

Should go, either tic, or tac.

Fast together... tictac. Haha. ;)

Regards,
aam.
Ok thanks. I'll try.
 
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