SL300 interior light and Hot start problem

[blacksl]

SL300 interior light & power seat problem

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First,
My 4 interior lights come on when the passenger door is opened, but do not when the driver door opens & it is not the door switch. No blown fuses under the hood or in trunk. Also, the interior/dome light does not come on with either door open, when the switch is in the correct position .

Second,
the car will start great when cold, but after driving it for 15 minutes or so
then try to start it, will start then die down, only after few attempts it will start again also I am getting a poor gas milleage
from what I have been reading could be the Fuel accumulator or Fuel pumps

Any ideas?

thanks
blacksl



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[tecqboy]

If the two lights in the lower door panels come on when you open either door, but the overheads do not, then the door switches are OK. The problem then lies in the overhead switches or the relay which turns all interior lights on when you hit the door unlock remote key. There is a timer involved also. But, I think I'd start by replacing the two overhead switches. They are cheap and the most likely culprits. I had the same problem. My 300Sl starts better when cold then when hot, but only to the extent that I may have to crank it twice when hot. It helps on a hot start to hold the excelerator open just a bit, as it seems to idle too lean after a hot start. My gas mileage on my 1991 300Sl is about 18 to 19 in mixed city/ hwy driving ( 2nd gear starts) and around 23 to 25 on 100% Hwy at 65-75 mph. I keep accurate records; not just reading the mpg meter. I drive with a very lite foot. Anyone who says they are getting better mileage would have to prove it to me. But my JEEP G.C. only gets 13 city and 18 Hwy, so the SL is almost like an economy car in comparison.

[blacksl]

Techboy
thanks for the answer
the switches are working fine individualy at list when they are turned on position the right and left
but will not turn on automatically when doors are open .
so I guess the relay is next. problem is, the dealer sells the whole overhead
assembly unit for over $350.00
as for the hot start I will take your advise and just deal with it, no big deal.
however, the gas millage is very poor. I wish i can get that taken care of.

blacksl

[tecqboy]

The overhead light switches are multi contact. When they are in the center position, although the lights may be off, the switches themselves are still closing a contact set in the "a door may open" logic tree. You really need a diagram to understand the circuit. I had the same problem you discribe and one of the switches was faulty. A compitent shop should be able to fix this without replacing the entire controller.

So just how "bad" is your gas mileage?

[blacksl]

Thanks for the advice I will give it a shot with the switches
I will point this out to the shop tomorrow

I was trying to trace some wires with the overhead interior light under the the dashboard and noticed
No Horn, no head light,no signal light,no winshield wiper
I don`t know what happened. checked fuse no problem
Hope I did not screw something bad?

as for the gas millage I am getting 12/15 City/hwy

[blacksl]

since my last post regarding a interior light problem in 1993 300SL,
When I open the driver door no lights comes on from the overhead interior lights
or from the lower door panels HOWEVER when the passenger side door
is open everything work like it should.
"techboy" has suggested that it might be the switch or the relay inside the
interior light console or even the entire console.
so before I`m going to spentd big money on the interior light console, I "barrowed"( removed one from a friends car with the same vehicle 1993 300 SL) we tried it in my car. same problem again, overhead interior light and the door panel light works just with the passenger side door. But no driver side? UNBELIVEABLE!!!!!
so if its not the actual interior light console, What can it be???
ANY ideas?

Thanks

[tecqboy]

Well, sir, there is always the possibility that the pin switch in the door column is corroded or bad. I think this switch closes to ground when the door is open. My car is now in storage for the winter, so I can't go out and look, but I think this switch is easy to remove and check.

[bobterry99]

If the doorswitch is okay, then you may have a defective module that warns when the driver's door is open and the headlights are on or the key is in the ignition. Could be very easy and inexpensive to fix...When you have the driver's door open and the headlights on do you get the warning buzzer?

[blacksl]

Thanks for the reply techboy and bobterry99
first the door switches are good, I did swap them to make sure.
I do hear the buzzer when the key is in the ignition or the head light are on
could it be a defective moudle how do you fix it? where is it located?

Thanks

[bobterry99]

The door switch is wired to pin #7 of the warning module and the interior lights are wired to pin #5 of same. You know that the switch is working properly and grounding pin #7 since the warning works, so it follows that the module probably has an open circuit between pin #7 and pin #5.

Internal to the module there should be a diode connecting the two pins. The anode (+) terminal is on #5 and the cathode (-) is on #7. My guess is the diode is faulty or there is a bad solder connection. You can verify this with a basic multimeter.

If I am correct, you have several repair options. My choice would be to open the module and correct the problem. Another possibility is to wire a new diode between pins #5 and #7 external to the module. Diodes are available from Radio Shack. A rectifier-type diode would probably be a good choice here since it can carry plenty of current.

The warning module should be located immediately behind the right side of the passenger airbag. The airbag is easily removed. You'll need a 1/4"-drive 10mm socket and 6" extension. A single bolt secures the airbag from below. Just pry off the round plastic cap that is on the underside of the dash and remove the bolt. The airbag then lifts out.

[blacksl]

replaced relay that was located under the driver side seat
problem solved!

[tecqboy]

What relay was that? I didn't know there was anything under the seat that was related to the interior lights. I'm always learning stuff about this vehicle. I don't have a decent wiring diagram; that is, one that shows where various compoments are physically located. Thanks Tod

[FirstMerc]

If anyone knows where exactly under the driver seat this relay is located and what it looks like then please let me know. I've taken the driver seat bottom cushion out but I could not find the relay in question. Thanks.

[bobterry99]

Six months later I still don't understand how blacksl's problem got fixed. There is no relay under the left-side seat. There is a "safety package" control module (picture), however, and maybe this was construed as being a relay. But the thing is I can't come up with a plausible scenario where this module would have been the problem.

[Dec McDermott]

I appear to have a very similiar problem with the interior lights and "lights on" warning buzzer on my 1995 SL, can anybody please tell me where this relay is located before I loose another weeks sleep trying to figure out the problem !!
Many thnaks,
Dec.