w126 1986 300SDL -- no dash lights - PeachParts Mercedes-Benz Forum

daw_two · #1 11-02-2007, 11:18 PM

Yes, I know this has been posted before and I found several threads for cluster removal. So, here's my situation. I've got the cluster out -- broke the center tab out of the left most cable; glue tomorrow.

I took the cluster out because I have no cluster lights -- hate driving at night and not knowing how FAST we are going. I figured the pentiometer (fader) worked because the light behind the outside temperature gauge works. So, I get the cluster out and the brown light sockets at the top won't come out. The plastic is brown above the sockets and is melted. So, I remove the outside temperature display and the odometer to get to the front. It is definitely melted.

I get the 2 big bulb out along with the 2 small ones (what do they do? Back light the odometer?); measure the resistance on one of the big bulbs and it is 3 ohms. Go out to the car battery and bingo, it works. Now what? Is there a fuse someplace I should have checked first? I'm guessing that the Westinghouse 5W5 E12EC is too much wattage, right?

Any help here would be greatly appreciated. I'll post photos when I can get the digital camera interfaced.

Brian Carlton · #2 11-02-2007, 11:47 PM

First thing to do is to replace fuse 11.

After you have done that, turn the parking lights on and check for voltage at the rheostat, socket #5 on the 15 pole connector.

If you have voltage at #5, jump #5 to #8 and see if you get illumination on the bulbs.

daw_two · #3 11-03-2007, 12:08 AM

So, Brian. Are there 2 circuits within the rheostat? I'll give it a whirl after I replace the 5watt bulbs with 3watt bulbs in the morning. And one of the prisms looks browish --- have to wonder if my lights are going to look brown.

Thanks for the quick reply.

Brian Carlton · #4 11-03-2007, 12:13 AM

Quote:

Originally Posted by daw_two

So, Brian. Are there 2 circuits within the rheostat? I'll give it a whirl after I replace the 5watt bulbs with 3watt bulbs in the morning. And one of the prisms looks browish --- have to wonder if my lights are going to look brown.

Thanks for the quick reply.

The rheostat is a single circuit in series with the dash lights. I'm trying to see if you have power at the rheostat, and then bypass the rheostat to eliminate it from the circuit.

daw_two · #5 11-03-2007, 12:45 AM

Quote:

Originally Posted by Brian Carlton

The rheostat is a single circuit in series with the dash lights. I'm trying to see if you have power at the rheostat, and then bypass the rheostat to eliminate it from the circuit.

the rheostat dims and brightens the outside temperature display.....so, it must be working, right?

EDIT: While I'm in here, I might as well try to make the RESERVE light work on the fuel gauge work, too. Should it come on initially like in my 300D when the key is turned to position #1? What watt bulb is that tiny thing?

Thanks!

Brian Carlton · #6 11-03-2007, 09:30 AM

Quote:

Originally Posted by daw_two

the rheostat dims and brightens the outside temperature display.....so, it must be working, right?

EDIT: While I'm in here, I might as well try to make the RESERVE light work on the fuel gauge work, too. Should it come on initially like in my 300D when the key is turned to position #1? What watt bulb is that tiny thing?

Thanks!

Yes, that confirms that the circuit is functioning, so, you can forget about any fuse or rheostat issues.

Your problem is the bulbs and/or the sockets.

The reserve light doesn't work because of the accumulated debris on the fuel sending unit.........most likely..........and you'll have to remove the rear seat and pull that unit (need a big socket) and clean it with Brakekleen. That will restore function of the reserve light.

cdplayer · #7 11-03-2007, 12:43 AM

Quote:

Originally Posted by daw_two

Yes, I know this has been posted before and I found several threads for cluster removal. So, here's my situation. I've got the cluster out -- broke the center tab out of the left most cable; glue tomorrow.

I took the cluster out because I have no cluster lights -- hate driving at night and not knowing how FAST we are going. I figured the pentiometer (fader) worked because the light behind the outside temperature gauge works. So, I get the cluster out and the brown light sockets at the top won't come out. The plastic is brown above the sockets and is melted. So, I remove the outside temperature display and the odometer to get to the front. It is definitely melted.

I get the 2 big bulb out along with the 2 small ones (what do they do? Back light the odometer?); measure the resistance on one of the big bulbs and it is 3 ohms. Go out to the car battery and bingo, it works. Now what? Is there a fuse someplace I should have checked first? I'm guessing that the Westinghouse 5W5 E12EC is too much wattage, right?

Any help here would be greatly appreciated. I'll post photos when I can get the digital camera interfaced.

I just fixed my cluster lighting problem. Early on I replaced the stock dull light bulbs with a much brighter (blue) bulbs. Then the left bulb seemed to burn out. Not really though. Upon inspection, I saw the plastic "cups" had
distorted with the heat produced from these bulbs.

No matter what I did I could not get the bulbs to work.
So I got another speedo/circuit assembly at the junk yard. Wrong one.
Then I grabbed my Brumel and began to hone out the distortion on the plastic cups. Cool!

It seems the distortion was lifting the bulb off the circuit board just enough to break the connection. Plus it was really hard to remove and reinsert the bulb too. But not now.

daw_two · #8 11-03-2007, 01:17 AM

Quote:

Originally Posted by daw_two

Yes, I know this has been posted before and I found several threads for cluster removal. So, here's my situation. I've got the cluster out -- broke the center tab out of the left most cable; glue tomorrow.

I took the cluster out because I have no cluster lights -- hate driving at night and not knowing how FAST we are going. I figured the pentiometer (fader) worked because the light behind the outside temperature gauge works. So, I get the cluster out and the brown light sockets at the top won't come out. The plastic is brown above the sockets and is melted. So, I remove the outside temperature display and the odometer to get to the front. It is definitely melted.

I get the 2 big bulb out along with the 2 small ones (what do they do? Back light the odometer?); measure the resistance on one of the big bulbs and it is 3 ohms. Go out to the car battery and bingo, it works. Now what? Is there a fuse someplace I should have checked first? I'm guessing that the Westinghouse 5W5 E12EC is too much wattage, right?

Any help here would be greatly appreciated. I'll post photos when I can get the digital camera interfaced.

Okay, I see the 2 small bulbs are my turn signals. Which work, of course. It's amazing what you can learn by looking thru the cluster from the back side. Got to remember to clean the back of the plexiglass, too.

sixto · #9 11-03-2007, 02:07 AM

Paint the bulb surroundings gloss white or silver to maximize reflectivity (is that a word?).

Sixto
87 300D