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Discussion Starter · #1 ·
I have no illumination on any of my dash gauges on my '76 450SL. I guess there's the possibility that they've all burned out and need to be replaced. Before I remove the steering wheel and the dash to replace the bulbs I figured I'd ask the forum if they had any other items I should check first.
 

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1977 450SL
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117 Posts
Instrument cluster has only two bulbs. Do the climate control lights work? Does the dim adjust rheostat work? they are famous for failing, try twisting ist back and forth to see if you get a flicker. The rheostat controls both instrument cluster bulbs and the 3 climate control bulbs. One of the climate control bulbs is actually behind the cap of the AC Control switch, another illuminates the blower switch and the third is in the center of the climate control panel. The two in the instrument cluster are on long tubes between the speedometer and the other two gauges sets.
 

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1988 560SL Currently, 1972 350SL (RIP)
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Always worth a check of the fuses also. I’m sure you know but just in case not it’s on the footwell outside wall of the passenger side. If they aren’t new it’s worth taking them all out, wire brush clean all contacts and replace with new high quality fuses. Something that should be done anyways and it’s slightly possible it could be that simple.
 

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Discussion Starter · #4 ·
Instrument cluster has only two bulbs. Do the climate control lights work? Does the dim adjust rheostat work? they are famous for failing, try twisting ist back and forth to see if you get a flicker. The rheostat controls both instrument cluster bulbs and the 3 climate control bulbs. One of the climate control bulbs is actually behind the cap of the AC Control switch, another illuminates the blower switch and the third is in the center of the climate control panel. The two in the instrument cluster are on long tubes between the speedometer and the other two gauges sets.
Thanks for the reply. No...I do not have any lights on the climate control panel. I believe there's also supposed to be a light on the shift indicator which is not lit either. I twisted the rheostat back and forth many times but it has no affect at all.
 

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1976 450SL, 1992 190e 2.3, 1984 300D turbo, 1966 VW bus
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392 Posts
All the bulbs are on the same circuit. I would pull the cover around the shifter. Be careful to not break the pin on the back of the panel. The whole panel needs to slide back then up (see photo)

Pull the bulb and see if the filament is burned out. Test socket to see if you have power when headlights are on.

If you aren’t getting power to the bulb it is probably the rheostat, you will have to remove steering wheel and instrument cluster. It’s not as bad as it sounds as long as you have a big breaker bar and correct allen socket. The Mercedes logo on the steering wheel can be carefully pried out with small screwdriver to reach bolt.

Just hold a test wire to the rheostat to bypass it.

It could also be a plug that has worked loose on the back of the instrument cluster, this happened to me once. One loose connector behind gauges and all the lights will go out, they are all connected.
 

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Discussion Starter · #8 ·
All the bulbs are on the same circuit. I would pull the cover around the shifter. Be careful to not break the pin on the back of the panel. The whole panel needs to slide back then up (see photo)

Pull the bulb and see if the filament is burned out. Test socket to see if you have power when headlights are on.

If you aren’t getting power to the bulb it is probably the rheostat, you will have to remove steering wheel and instrument cluster. It’s not as bad as it sounds as long as you have a big breaker bar and correct allen socket. The Mercedes logo on the steering wheel can be carefully pried out with small screwdriver to reach bolt.

Just hold a test wire to the rheostat to bypass it.

It could also be a plug that has worked loose on the back of the instrument cluster, this happened to me once. One loose connector behind gauges and all the lights will go out, they are all connected.
Thank you for your reply
 

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1977 450SL
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Fuse 10 is Brake lights, back-up lights, combined instrument, tachometer. Please complete you profile with car information...
 

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1976 450SL, 1992 190e 2.3, 1984 300D turbo, 1966 VW bus
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yes, obviously you need to check fuses. i assumed you already did that..
 
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