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Registered
1972 350SL VIN 107.044.12.000068
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137 Posts
Discussion Starter #1
Hey guys, this is my first question post (be gentle!) and so here goes:

My '72 350SL had an unsightly situation involving a badly cracked console, which had been cut for an aftermarket radio, so it didn't connect to the dash properly. I replaced it with one from an '83 and rehabbed everything and it looks really nice.

Unfortunately though, I left a wire loose (the black one that comes from the clock, I now realize) and it cost me a fuse or two till I figured it out.

Now I have it hooked to the right place (one of the lightbulbs behind the climate panel) but -- no light from either the clock, the radio, or the climate controls. I get lights from the shifter, the hazard, and the instrument cluster, but not from the clock "on out". Fuse is intact, and other things on that circuit (license plate light etc.) all function when the headlights are on.

This seems to have happened after I installed the original Becker radio back into the car, but I'm not 100% certain. I took the radio back out and the lights still don't work. :confused:

I've tested the bulbs (they work) and I can get 12V power on the light socket that I hooked the wire from the clock to, so it appears somewhere there's a circuit open? Anyone know what I should try here? Is there a ground wire for those lights and if so, where is it and what does it look like? I'm not an electrician, but I play one on TV.

Thanks in advance!
 

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Premium Member
1983 380SL, 2000 S430, 1991 420SEL (retired) - RHD
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5,500 Posts
Ground wires are brown. Maybe one's come adrift.Do you have a manual? If not you can download a freebie from the sticky section .
 

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Registered
1972 350SL VIN 107.044.12.000068
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137 Posts
Discussion Starter #3
Thanks Aussiemerc, I will have to check to see if one has come loose somewhere. I've got a manual, what I need is more knowledge!

Just plugged the radio back in and now it's not working either/light isn't coming on, even though I have tested it and the bulb does work...any other thoughts?
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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29,492 Posts
Sounds like a real clusterfuck.


Add an additional ground to the cluster before you waste anymore time.

That USUALLY fixes most issues.
 

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Registered
1972 350SL VIN 107.044.12.000068
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137 Posts
Discussion Starter #5
Great idea, I'll try that. I'm having some other issues in the cluster (i.e., potentiometer kills all the lights if I touch it, and the parking brake warning light stays on permanently) so I bet there's something there. Thanks for the tip!
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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29,492 Posts
Great idea, I'll try that. I'm having some other issues in the cluster (i.e., potentiometer kills all the lights if I touch it, and the parking brake warning light stays on permanently) so I bet there's something there. Thanks for the tip!
Spin that potentiometer about 50 times back and forth. That might do the trick.


Or...STOP TOUCHING IT!!!
 

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Registered
1972 350SL VIN 107.044.12.000068
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137 Posts
Discussion Starter #7
Or...STOP TOUCHING IT!!!
LOL I keep trying to see if maybe this time...(twist) - boom - nope, still busted.

I am going to pull the cluster tomorrow and add a ground, will let you guys know how it goes!
 

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Always Remembered RIP
1979 280sl 4 sp w/ac 1957 MGA 1998 volvo xc/70 2004 F150
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6,050 Posts
You can take the dimmer switch apart and clean it. Drill out the 2 rivets, clean the contacts and assemble with small screws and nuts. There's pics somewhere but I can't fine them.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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29,492 Posts

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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32,318 Posts
Brake warning light. Pull the release and pull the pedal all the way up then let go of the release knob. The pedal may not be returning all the way.

Did you check the bulb in the clock?
 

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Registered
1972 350SL VIN 107.044.12.000068
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137 Posts
Discussion Starter #13
Cluster ground seems to have helped

OK, here's the update. I pulled the cluster today (was happy to have a chance to clean the backs of the gauge lenses, which had some kind of sticky crap on them but now look new) and only lost one bulb holder, which popped off and went somewhere back in the dash in the process, not too bad...

BUT the chassis ground seems to have done the trick, because now I have lights in the console! That rocks, thanks guys. I found a wire that someone had spliced into the clock to give constant power to the aftermarket radio, and I managed to get that wire out, so things are back to original and seem to be working well. Cool!

I also lubed the speedo cable with dry graphite while I was in there, which seems to have helped a bit with the squeaking and bouncing, but I'm thinking it might need something more.

rowdie, I tried your suggestion on the brake, no luck. It seems to be electrical - I even pulled the switch/relay thing at one point and it still stays on. I'm not sure if that switch is removed, why would the light stay on? Any ideas there? Maybe another ground issue? Wiring diagram shows a ground but I can't imagine that with the switch totally removed that it would be a ground fault...seems like something in the cluster itself?

Thanks for all the help guys! I bought a set of five bulb holders for the cluster on ebay, I just need 1-2 (1 for an extra), so if anyone needs one, let me know and I'll send one your way. My way of saying thanks to the forum! :)
 

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R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
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Warning light may be low fluid in the reservoir. With one that old it could be a stuck float or even broken wires to the sensor.
 

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Registered
1972 350SL VIN 107.044.12.000068
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137 Posts
Discussion Starter #16
Warning light may be low fluid in the reservoir. With one that old it could be a stuck float or even broken wires to the sensor.
Thanks rowdie, what the problem was, was a busted float. I opened the front tank and the stem was just laying there, did not float up. I removed it so that the light would function properly, of course there's no warning now but I'll see if I can find that float somewhere online and replace it.

MB manual talks about bleeding brake system annually and replacing fluid, is that something you guys do? Seems extreme.

Also, lights were working last night but somewhere I still have a fault/short as I blew another fuse. :( Gonna have to pull that console again, I'm afraid....
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
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29,492 Posts
MB manual talks about bleeding brake system annually and replacing fluid, is that something you guys do? Seems extreme.
Not ever year...but I've bled the whole system 3 times in 7 years.

It's an easy job to do with a pressure bleeder and fluid is cheap...so why not?

The colour of the old fluid might surprise you.
 

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Premium Member
1991 560 SEC Black/Black
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164 Posts
Good Morning All,
I am about to pull the instrument cluster out of my 1979 450slc and I was hoping someone could tell me something about the socket type and size that I am going to need in order to take the steering wheel off. I have a new cluster pot to install and don’t want to open any other cans of worms in the process. Also, when the weather is cold I get a God awful squeal that is coming from the instrument cluster any ideas on this before I dive in.

Thank You
 

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Registered
1972 350SL VIN 107.044.12.000068
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137 Posts
Discussion Starter #19
Good Morning All,
I am about to pull the instrument cluster out of my 1979 450slc and I was hoping someone could tell me something about the socket type and size that I am going to need in order to take the steering wheel off. I have a new cluster pot to install and don’t want to open any other cans of worms in the process. Also, when the weather is cold I get a God awful squeal that is coming from the instrument cluster any ideas on this before I dive in.
If you pop out the center cap with a screwdriver, you can see the nut easily and size it that way - I think mine was 19mm or 20mm (72)

The squeal might be speedo cable, I put some dry graphite lube in mine (squeezed it in as much as I could from the free end behind the cluster) and it helped a bit, but not entirely. If your speedometer needle bounces, it's almost surely the cable. Might have to pull mine and rehab it the "right" way.
 

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Outstanding Contributor , Bob's Your Uncle!
-----'83 280 SL----- 5 speed....The PIG
Joined
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29,492 Posts
Good Morning All,
I am about to pull the instrument cluster out of my 1979 450slc and I was hoping someone could tell me something about the socket type and size that I am going to need in order to take the steering wheel off. I have a new cluster pot to install and don’t want to open any other cans of worms in the process. Also, when the weather is cold I get a God awful squeal that is coming from the instrument cluster any ideas on this before I dive in.

Thank You
http://www.benzworld.org/forums/r-c107-sl-slc-class/1495136-odometer-repair-tutorial.html
 
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