1982 380SE Instrument lights

[corvus]

Hi all,

All internal lights have gone out on our 380se. Since this has happened there is a drain on the battery even with the ignition key out.

I've checked in & under the fusebox under the hood/bonnet and found all wires to be ok.

I want to get behind the dash where the ignition and driving light switches are but cannot find a way in.

I spoke to Haynes and they have a manual being sent from the States but this will only cover the engine...

Funny thing is when I put a meter between the battery terminal and it's connector to see if there is a voltage drain, it shows continuity for a few seconds then goes out. Then the meter only shows continuiry if I reverse the probes! It only shows a drain again if I wait 20 seconds and reconnect the meter!!

Could it be the alarm and if so, where is it?

Any advice for the hopelessly confused?

 

[paulcallender]

Any advice for the hopelessly confused?

Don't run with scissors?

No but seriously, it sounds like you have a wire which is the +12V feed to the lights, which has worn through and is arcing to earth, somewhere. This would cause a current draw and could also disable your lights.

Best bet would be to place an AMMETER (not voltmeter) in series to the battery. Then pull each fuse in turn, and see what the current draw is. By placing a meter configured as a voltmeter in series, you're not really measuring anything, since a voltmeter's resistance tends towards infinity. An ammeter's, tends towards 0.

I think all alarms in 1982 were aftermarket fitments (although by the dealer, before the car was sold), so I can't be sure of its location. If it helps, mine's on the right inner wing, under the bonnet.

 

[corvus]

Hi,
I was using the meter set to check continuity. As I thought the meter may be duff, I used a light bulb in series instead.

Same thing though - when first connected the bulb is bright for a few seconds then it fades off. Leave it off for a few seconds and it's bright again but fades off.

It's not the battery as the headlights work ok.

To check the instrument illumination as being the prob I need to get into the dash but the 380se is built like a bomb shelter and I don't have a manual.

I bought the dvd version on ebay and just get errors when installing it so am reluctant to waste meny on more.

 

[paulcallender]

You must connect a voltmeter in parallel with the thing you're measuring; and an ammeter in series. Otherwise the readings will not reflect what you want to measure, and you may even damage the meter. To check continuity, you could use the resistance function on a multimeter - keeping the circuil connected and testing at either end - for example, if you are unsure a device is properly earthed, a resistance reading between its earth, and a known good earth, would soon tell you. The bulb will give the same results as a voltmeter, except it won't really give an accurate indicaton of the state of it - it will tell you if you have +12V or 0V, though.

I think an 82 S class dash is the same as W124 - you can lever it up with some kind of lever, at either end, making sure you don't scratch the rest of the dashboard. Even with the speedo cable still connected, this should give you enough room to remove/replace bulbs, with small hands.

 

[Keith]

pushing out instrument cluster

I think an 82 S class dash is the same as W124 - you can lever it up with some kind of lever, at either end, making sure you don't scratch the rest of the dashboard. Even with the speedo cable still connected, this should give you enough room to remove/replace bulbs, with small hands.[/QUOTE]

on a W124 its easy to remove the lower dash then put your hand/fingers up behind the instrument cluster and push out from behind with speedo still attached, its just held by friction. this avoids risk of damage by sharp tools etc. hope this helps not sure if same on an S
Keith

 

[corvus]

Hi Keith,

That was easy. I took the panel off and all wires looked ok.

I took the battery to two shops and both tested it as ok.

The other day I decided to disconnect it, fully charge it and try starting again but no joy.

I used jumpers to another battery and it's fine.

Definitely a duff battery!

Looks like the dash lights goind out was a coincidence.

Now I'm trying to locate the bulb but all switches seem to be lit by fiber optics.

Any suggestions?