Author Topic: Hanging Plug (Read 9209 times)

recips · « **on:** April 14, 2018, 17:59:32 »

This has been hanging taped up on the car since I bought it but I would like to put it back as it should be. 1- What is it and 2- Why would it be disconnected? Thanks, Eric

Pawel66 · « **Reply #1 on:** April 14, 2018, 19:49:51 »

the shape of rubber cover reminds me the one for thermo switch or thermo-time switch. Depending on the car model it is located either near cylinders 2/3 or higher in the block near cylinder 6.

recips · « **Reply #2 on:** April 14, 2018, 22:59:00 »

It's a 71. I've had the car for 4 years and it has never been connected. Has it been bypassed or is it not necessary? Thanks

Iconic · « **Reply #3 on:** April 14, 2018, 23:09:57 »

Are we possibly looking at the headlight "dimmer" switch?
If so, might I ask if your brights work from the switch on left floorboard on a LHD car?
What car are we talking about here? 280 ? LHD ? Year?

Mike Hughes · « **Reply #4 on:** April 15, 2018, 00:11:35 »

If I am looking at this photo properly I am seeing a LHD vehicle, with the bottom of the steering box inboard of the "frame rail" at the very top of the photo, and the switch you may be referring to is also inboard of the "frame rail." The dimmer switch is located outboard of the "frame rail" on a LHD vehicle. What switch would be on the floorboard essentially behind the accelerator pedal?

Pawel66 · « **Reply #5 on:** April 15, 2018, 09:13:36 »

Quote from: Mike Hughes on April 15, 2018, 00:11:35

If I am looking at this photo properly I am seeing a LHD vehicle, with the bottom of the steering box inboard of the "frame rail" at the very top of the photo, and the switch you may be referring to is also inboard of the "frame rail." The dimmer switch is located outboard of the "frame rail" on a LHD vehicle. What switch would be on the floorboard essentially behind the accelerator pedal?

If it is an automatic that would be the kick down switch, I suppose.
I think I am sticking to my theory. This plug may be hanging from above there. Simple test (if it is still wired) would be to see if you get "+" on one of the wires in the plug when you crank the engine.

What wire colours are there in the plug? Are there two wires? Is one of them pink?

Iconic · « **Reply #6 on:** April 15, 2018, 15:44:09 »

I stand corrected Mike and Pawel, thank you !!
Auto trans kickdown switch makes sense ... if the car is an automatic.
Maybe the OP (original poster) could tell us what kind of car, if it is automatic.
A few more pictures would help too.
We love mysteries, right ??

Pawel66 · « **Reply #7 on:** April 15, 2018, 15:59:21 »

The mysteries are so irritating that you would just want to resolve them to get them out of the way...
I like them when I fidure out solution. Otherwise I do not like them.

If it is a kickdown switch there, I think it is missing the plug retaining spring. And it is missing the plug. Wiring is a bit messy on the contact plate.
I think I see the left hydraulic switch on the automatic transmission (with the black plastic nut).

But I may be wrong.

Benz Dr. · « **Reply #8 on:** April 15, 2018, 20:18:58 »

Quote from: Pawel66 on April 15, 2018, 15:59:21

The mysteries are so irritating that you would just want to resolve them to get them out of the way...
I like them when I fidure out solution. Otherwise I do not like them.

If it is a kickdown switch there, I think it is missing the plug retaining spring. And it is missing the plug. Wiring is a bit messy on the contact plate.
I think I see the left hydraulic switch on the automatic transmission (with the black plastic nut).

But I may be wrong.
[/quote

I see that too. I think I also see that there isn't a wire on the pressure switch.

recips · « **Reply #9 on:** April 17, 2018, 01:26:23 »

I've been away on business and without internet access for the most part so sorry for the late reply and thanks to all for their input. The car is a '71 280SL, automatic and LHD. I will attach a few more pics later. Again any help is greatly appreciated. Thanks, Eric

recips · « **Reply #10 on:** April 17, 2018, 01:28:25 »

recips · « **Reply #11 on:** April 17, 2018, 01:33:33 »

mrfatboy · « **Reply #12 on:** April 17, 2018, 01:42:40 »

Post some pictures of the engine bay from the top so we might see what is missing. My current guess is the thermotime switch connector.

recips · « **Reply #13 on:** April 17, 2018, 02:02:25 »

I'll get those up tomorrow when I get home from work. Thanks

Pawel66 · « **Reply #14 on:** April 17, 2018, 07:30:04 »

It is difficult to say what colour are the wires. If one is pink and the other pink/blue (move the insulation a bit to see if there is a second colour on the wire) - then it is the thermo-time switch plug. Be careful as you may be getting "+" on the pink/blue wire (if it is still connected) when you crank the engine.

Thermo-time switch is part of starting aid for the engine - it provides ground in certain conditions to a relay that activates the Cold Start Valve that injects aditional fuel to the manifold to make start easier. The Thermo Time switch is in the engine block, its upper part, drivers side, near 5th and 6th cylinder. Apparently you have it wired in a different way or you have troubles starting the engine. Lots of info on this on the forum (Thermo Time Switch or TTS).

If the colours are different - then I do not know, we would have to know the colours to check on the other fellow Mambers suggestions.

I would also review the wiring on the contact plate on the gear box - it looks different from what I remember from my gear box, but maybe it is just a different type of solution (emission control?). The contact plate should have a cover. There is no wire on the hydraulic switch (under the plastic nut). Do you have issues of engine stalling when you put in Reverse gear? Do you have idle speed adjusted by a solenoid on the intake manifold? This switch, in some engines, activates the solenoid that increases idle (Constant Speed Solenoid or CSS) when reverse gear is selected. Again - in your car there may be a different system to do it (emission control?, CSS sometimes works for air condition only).

Normally on the kick-down switch you have a 2-pole plug and a retaining spring.

I see also some lose wire hanging there with eye connector - maybe it is better not to leave it hanging...

recips · « **Reply #15 on:** April 20, 2018, 22:59:47 »

Additional pics

recips · « **Reply #16 on:** April 20, 2018, 23:01:21 »

recips · « **Reply #17 on:** April 20, 2018, 23:02:05 »

recips · « **Reply #18 on:** April 20, 2018, 23:03:47 »

recips · « **Reply #19 on:** April 20, 2018, 23:05:08 »

recips · « **Reply #20 on:** April 20, 2018, 23:07:03 »

I took the pics with my phone so I may not have exactly what I think you guys want. Let me know your thoughts. Thanks, Eric

66andBlue · « **Reply #21 on:** April 21, 2018, 01:35:45 »

'recips' what model do you have: 230SL, 250SL, 280SL??? Please add this information otherwise we are flying blind.
Looking at your photo it almost looks like you have a thermo switch (yellow arrow) and a thermo time switch (green arrow) installed in your engine.
Search for these two parts here and you may find out what you need.

Pawel66 · « **Reply #22 on:** April 21, 2018, 08:34:13 »

From Alfred's picture:
- in 280SL engine, where Alfred placed the right hand side yellow arrow, there should be a Thermo Time Switch (or TTS). That is where I think the hanging plug belongs to. Indeed on the forum and Technical Manual you will find information on the original pieces as well as about at least two of its replacements (Bosch, Mercedes).
The Thermo Time Switch is responsible for cold and also hot start - they activate Cold Start Valve through a relay to inject additional portion of fuel to intake manifold.

Do you have engine starting isues? If you do - this may be one of the potential reasosn. Unless someone found some new creative solution in your car....

- the left yellow arrow on the picture - I think you should have engine temperature sensor there with a line to gauge in the dashboard (please correct me if I am wrong). Are all of your gauges (temp, oil pressure) work properly? If so, then there is some other solution installed in the car.

ja17 · « **Reply #23 on:** April 21, 2018, 13:36:57 »

Definitely the themo time switch wiring. The type of wire braiding, the colors and the ring terminals all indicate tts. In addition, the non-original sensor in the head indicates some incorrect modification. Remove the tape from the end of the wires and the two ring terminals should be slightly different sizes.

Also I noticed you do not have the "self centering" nuts on the engine linkage support. Also notice the radical modification to the hood latch? (most likely done to make valve cover removal easier??!)

recips · « **Reply #24 on:** April 21, 2018, 14:06:43 »

The car is a '71 280SL, LHD and Automatic. It seems that the consensus is that the thermo time switch has been "Bubba-ed". I will look into what I need to do to put it back in proper order. I will say though that I had never had issues starting the car cold or hot. I do live in North Carolina and really don't drive the car on particularly cold days so that may have been to my advantage. As far as the linkage nuts and the hood latch I will have to look into those. Anyway thanks to all who replied and I will post what I wind up doing. Great forum! Regards, Eric

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Author Topic: Hanging Plug (Read 9209 times)

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