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Discussion Starter #1
My 1988 560SL had this same issue once before, but it went away within a day. Basically, the speedo, tach and rest of the instrument cluster, along with the power windows, brake lights and turn signals, are inop. I've checked all the fuses, which look fine, although I did not see a fuse for anything except power windows. I dropped by my friendly mechanic, who said it might be a relay. Is there one relay which controls all these items, and where is it located? Thanks for your help!
 

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Same happened on my 84 280sl last week (except the speedo worked), fuse was good, fuse contact was not. Spin them in place and see if it corrects the problem. Next would be to add a ground wire to the back of the cluster.
 

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Discussion Starter #4
Is there one relay that controls all these electronics? Is it located above the fuse panel or behind the dash somewhere?
 

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If you haven't done so clean the contacts and replace with brass tipped fuses. Also I had a similar problem on mine. The star connector on the back of the instrument panel came loose and eventually fell off. If I remember correctly I had to remove the driver's side front speaker to get my hand up in there. I am betting on Dave's solution by the way...I had some of the same problems as you but not all.
 

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Just as a precaution: Get some electrical terminal grease from the parts store, it should come in a small packet for very little.

Take each fuse out one at a time, and buff the ends with a coarse cloth, such as denim or canvas, you want to polish them up a little bit. Add a tiny dab of grease to the ends, and reinstall.

The grease keeps moisture and air away from the contact surfaces, preventing corrosion. The original fuses are aluminum, and the holders are brass. The disimilar metals will corrode with oxygen and moisture and electrical current, creating an insulating layer of corrosion.

Scott
 

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Discussion Starter #9
tresfenton, were you able to check the over voltage protection relay?
Not yet. I'm waiting for my mechanic to get back with me to set up a time to go over there. I'm not quite as mechanical as most of you guys. I just like having ideas to tell the mechanic if he doesn't already know exactly where to look to solve a problem on the 560.
 

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Fuses can be questionable, and as suggested you might spin them in place, but sometimes this causes them to wrap around the insulator, not really something you want happening. The fuse location is so awkward to start with that fuse replacement is difficult at best. Take your brass or copper fuses and soak them in white vinegar overnight, they will be cleaned and etched to as new condition, even better than new. That will rule out conductivity.
 

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Excellent advice for those who have no understanding of electricity not to mention DC. The latest issue I my 79 450 SLC through at me was all my interior lights were out, drivers side window and rear passenger side windows dead, head lights out cold, hazard flashers gone, rear marker and tail lights sleeping. Sound familiar to you guys..

GROUND, GROUND, GROUND, as mentioned by GOHOT and RADIO TEK connection condition is the key here.

With that said I thought I remembered seeing something in this forum or in a service manual about where all the grounding locations for this vehicle are located. Can someone point me in the right direction on this it sounds like the old 450 is trying to tell me something.

Thanks
 
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