warning module and '75 450SL

domchang · #1 10-20-2001, 01:07 AM

I've searched through this forum and the owners manual, cannot find a specific reference to this:

On a 1975 450SL, is there supposed to be a warning buzzer that warns you when you leave the lights on? I drained the battery this morning when I did this and had to jumpstart the car.

I do get a warning buzzer if I leave the keys in the ignition and I open the driver's door so I know the warning module is working.

Also noticed that there's supposed to be a lightbult in the the headlight switch( the bulb is missing) which looks like it would illuminate the green dot on the headlight switch cover. Anyone know what type of lightbult I need to ask for at the local autoparts store or is this a MB only kind of lightbulb? I figure if this light is lit while the lights are on, it might actually clue me in that I left the lights on again! Senility, what a concept. : )

thanks

dom

MikeTangas · #2 10-20-2001, 01:38 AM

Dom,

Actually, I believe the green dot on the headlight switch is only illuminated when the fog lights are on. If your car is fitted with the factory fog lights once the headlights are one, pull the switch out one notch. That should activate your fogs and illuminate the green dot.

The second notch out is for the rear fogs, which I don't believe your car has, unless it's a Euro model. Most of the newer Benz's sold in teh States have the rear fogs as well (the rear fogs only light one side of the tail lights brighter, usually the driver's side).

Gilly · #3 10-20-2001, 01:38 AM

Hi:
Yes, I believe this car has this feature. It should work when the key is off, the lights are either in park or headlight on position, and the drivers door (only) is opened. Do the dome lights come on with the drivers door opened? If not, it may be the drivers door jamb switch is not working and not allowing the dome lights or buzzer to work properly. if the dome lights do work, it may still be the switch, wiring, or just a bad buzzer unit, the buzzer unit itself has circuitry inside it which can fail, but the door jamb switch, due to the moving parts, would be more suspect, also wiring on an older car like this.
The small dot in the middle of the switch is to indicate the foglights are on. start the car, turn on the headlights OR parking lights and then pull out on the knob, that turns on the fogs. I don't believe this car has rear fogs,. I if it did, the knob would pull out to 2 different detents, the first detent is front fogs, the second detent turns on also the rear fog. If the car was designed for rear fogs, it may not be wired for it in a US spec car, but the second detent may be in the switch (same switch for most versions).
Gilly

domchang · #4 10-20-2001, 11:01 AM

Thanks for all the replies - some clarification:

I was not clear enough in the initial posting.

The car does not have the hardtop on at this time so no dome lights to check. I don't recall any on the hardtop anyway, and since it's stored away elsewhere, can't run out to check it.

Yes, it's got the factory front fog lights but even though they work fine, the bulb itself is missing so unable to check to see if it comes on with the fog lights are on. However, knowing that this is the function of the green light, it's a small matter, since I was thinking it would help warn me when I leave the lights on in the car.

Come to think of it though, once I replace the bulb, and I drove with foglights on(to make myself more visible since the main headlamps are so weak)then I would see the green light still on when/if I left the lights on after shutting down the engine.

Not sure the door switch is the problem, the warning module does buzz at me when I open the door and the keys are still in the ignition...does that not signify proper operation? Or could the warning module still have partly malfunctioned and not give a warning when the lights are on and the engine is off?

Is there an aftermarket warning device I can hook up to my '75 450SL that will give a warning if I leave the lights on?

thanks for all the feedback so far.

dom

domchang · #5 10-21-2001, 04:21 PM

re the enabling of a warning buzzer when one leaves the car headlights on after turning off ignition.

found a link on the Net which describe a similar problem and a solution for the Mazda Miata...figured the principle would be the same for my Mercedes.

Following procedure will cause a warning tone to sound when you leave your headlights on with the ignition turned off on a 1975 450SL...am sure it'd work for other years/models but have only successfully done it on this particular one.

1. Go to Radio Shack and get pn#: 273-059 (less than $3). Its called a 12VDC Piezo Buzzer.

2. Remove cover from your fuse box (on my car, located in right side of passenger footwell), and locate fuses #5 and #16.

#5 description: windshield wiper, windshield washer pump, horn, pass signal light, cigar light.
#16 description: standing left light, parking left light, tail light left.

3. Hook the red wire from the buzzer to the fuse holder on fuse #16 by removing fuse, connecting the wire to the hole that holds the fuse in place, replacing the fuse to hold the wire in place.

4. Hook the black wire from the buzzer to the fuse holder on fuse #5, same as above step..

note: I extended both wires that came with the buzzer as they were kinda short.

5. Fold the wires and buzzer into the fuse compartment and replace the cover.

That's it! Now if I leave the headlights/parking lights on with the ignition in the off position, the buzzer tone sounds loudly enough to get my attention and remind me to turn off my lights! If the ignition is turned on, the buzzer does not sound when I have the lights on.

Hope this helps other people who tend to leave their lights on for whatever reason.

dom

Gilly · #6 10-21-2001, 10:03 PM

Dom:
I think alot of owners of a car like this would rather repair to MB spec, rather than a cure like this, but if you're happy with the results, that's great.
In reply to one of your posts in regards to the dome light in the hard top, the dome lights on this car are on the soft trim under the header panel. Hard to describe further than that. They are outboard of the inside rear view mirror about 6-12 inches, kind of in front of the sunvisors. They don't come off with the hardtop. The wire that is removed when removing the hart top is for the rear window defroster in the hard top back glass.
Gilly

domchang · #7 10-21-2001, 10:14 PM

yep, am happy but understand that a lot of people would rather do it to MB specs...I posted it just FYI for forgetful people like me who wanted a quick fix before the next time they left the lights on! : )

Will look for these dome lights....

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