3 Position Solenoid-- SUCCESS

[Ben]

Hello everyone, I've been lurking for a long time, since my W113 isin storage, this question relates to my W111, and yes I know I m being cheeky but the knowledge here is the best  ?

I would like to tap into the collective wisdom of all here, I believe my solenoid is not working correctly. I have all sorts of issues with the trans which happened suddenly.Perfect one day, next day the car was slipping and behaving very strangely. It will only drive normally if I give it over 3/4 throttle, and its is perfect if I hit the kickdown switch. On light throttle it slips,change up,down, back and forth etc..

I removed the inspection cover to check the solendoid, half the time it works, always gives a good click on kickdown but otherwise it sometimes clicks and then he rest of the time it makes a noise but hardly moves.

My venturi switch shows 0.4Volts on both connetions at all times, as I move the throttle valve it immediately shows 6-7 volts, then at about 3/4 it shows 12V and the solenoid clicks, then clicks back when the throttle is released, which all seems odd.

Anyway I have a spare solenoid but my question is can it be changed without dropping the trans. I will have access to a vehicle lift so could probably drop the rear down a bit, I want to change a mounting anyway.

[Shvegel]

Generally solenoids don't get weak. They either work or they don't. It would seem more likely that you have bad contacts on one of the switches or the connection block under the car. I would also check the linkage to be sure it is free. Does it move easily by hard?

[Ben]

Yeah thats very true but I have already removed and cleaned all the connections to no avail. Any opinion on those voltages I have at the switch ?

I can move the linkage no problem, it doesn't move very much but its not sticky.

I might try to hot wire the solenoid and see what happens. I have a spare solenoid but dont have a switch to try.

So can the solenoid be changed with the box in place. I would book some ramp time if it was possible.

[ja17]

Hello Ben,

The solenoid regulates the modulator pressure at different throttle positions. Remove the access cover on the tunnel inside the car to observe the working of the linkage and solenoid. At idle in drive with the linkage on its stop at the venturi, the venturi switch should be activated and move the transmission linkage to its rearmost position.

When the linkage is depressed the swich should break the  contact and the linkage should move to its center "rest" position increasing modulator pressure.

At kickdown the kickdown switch on the floor activates the solenoid to move the linkage to the frontmost position and even higher modulator position.

Check the function first.  Makes sure the trans linkage and pivots  are  not binding use some penetrant to free everything up.

I have a lot of additional information on settiing up the modulator pressure on these transmissions if you need it. There also is a rubber modulator diaphram in these transmissions which can rupture. If this happens you will notice whiitish/blue smoke from the exhaust and consumption of ATF.  Check your ATF fluid level.

Keep in touch.

[wwheeler]

I have been having problems with erratic kickdown and occasional hard downshift. Saw this thread and decided to test my solenoid circut. Can the solenoid be tested with the ignition switch @#2 position (fuel pump running/engine not)? Or must the engine be running and in drive?

I tested the:
Venturi throttle switch -  closed at idle and open at slight throttle
Kickdown switch - open until full throttle when it closes
Removed connections at trans wire terminal - Small wire from switch had no voltage until full throttle, medium wire from switch had voltage until throttle was slightly lifted and large wire from ? had no voltage but had continuity with ground. Voltage from switches was around 12 V.

So far so good? I did remove the access plate to look at the 3 position solenoid. Linkage moves OK, no binding. With the fuel pump running and engine off, the solenoid tended to stay in the middle despite the position of the throttle. When the kickdown switch was activated, sometimes the lever would move up and held it there. When the throttle was at idle, sometimes the solenoid lever would move down and hold but not often. I observed the linkage with the engine running, in PARK and at idle and still about the same result as above. Is this test valid or should it be done with the engine running AND in gear.

Finally, I've looked at the instructions from Sun Valley and also have a trans wiring diagram in German for a W113 '68 280 SL (Schaltplan W113copyright B. Meyer-Brockel, Eschborn) that I think I got from this sight but cannot find now. These two seem to contradict each other concerning which wires carry the power from the #3 fuse. Sun Valley indicates the large connector is the power wire and the small and medium wires (from the switches) are grounding. The German W113 diagram plainly shows that the switch wires carry the power and that the large wire is the grounded one. My tests seem to coincide with the German W113 diagram. Any thoughts on this or am I reading this wrong?   

Thank you for your input!   
   

[Peter van Es]

Did you get it from here: http://www.sl113.org/wiki/Automatic/Start

If so, please tell us what's wrong with that description so that we can make it accurate!

Peter

[Ben]

Hello Ben,

The solenoid regulates the modulator pressure at different throttle positions. Remove the access cover on the tunnel inside the car to observe the working of the linkage and solenoid. At idle in drive with the linkage on its stop at the venturi, the venturi switch should be activated and move the transmission linkage to its rearmost position.

When the linkage is depressed the swich should break the  contact and the linkage should move to its center "rest" position increasing modulator pressure.

At kickdown the kickdown switch on the floor activates the solenoid to move the linkage to the frontmost position and even higher modulator position.

Check the function first.  Makes sure the trans linkage and pivots  are  not binding use some penetrant to free everything up.

I have a lot of additional information on settiing up the modulator pressure on these transmissions if you need it. There also is a rubber modulator diaphram in these transmissions which can rupture. If this happens you will notice whiitish/blue smoke from the exhaust and consumption of ATF.  Check your ATF fluid level.

Keep in touch.

...............hello Joe, nice to hear from you again. I did remove the access cover and the linkage feels free.As I said there is not a lot of movement but once I turn on the ignition, car in gear, I feel it "crack" to the rear position. Also if I operate the kickdown switch it "cracks" to the forward position.

However I seems to stay in the rear position too long, i.e when I operate the pedal (or even the venturi itself) it does not release to its centre position until I am over 2/3rds throttle. If I drive the car and give it about 3/4 throttle or so it will drive perfectly, and it kicks down perfectly too.

So I am now wondering about the venturi switch, no matter what way I adjust it I cannot get it to both return to rear at idle AND move to centre position just off idle. I can only get it to do one or the other !

The curious thing is that whilst testing with the ignition on after I get the solenoid operating with a few loud cracks it then seems to get lazy. The sound certainly almost vanishes, yet the throttle switch seems to be giving me the same readings on the meter. It only gives a full 12V at 2/3rds throttle, yet it gives 6-7 volts just off idle.

That, to me, sounds as though the switch is the culprit (he says in hope) and since its easier to change maybe I should just get one !

Thanks you to all for your input, summer may be here we've had 2 days withoout rain   so I'd really love to get this sorted ASAP so I can take it to a few shows !

Oh BTW there does not seem to be any white smoke and the fluid level is correct, though I do top it up a little maybe twice a year but there was a slight leak previoulsy, now corrected. I have a few used trannys here that I could rob parts from too.

[bpossel]

Hi Ben,

You mentioned that this issue just started one day?  Think back...  did you work on the car prior to the issue?  What did you work on, what area(s)?  Double check all of your wiring and ensure all connections on the transmission are accurate and making a good solid connection and that all wires are well insulated and not touching each other with frayed insulation, etc...
When I put my car back together again last year, I had all sorts of shifting issues and it turned out to be a few wires going to the wrong places...  It made the trans do some really odd things... 

If you can think back on what you may have changed, touched, prior to your issue, it may help lead you to a solution...
Good Luck,
Bob

[wwheeler]

This is my experience but really think it would be wise to get some of the gurus who have done this test many times before to confirm before changing. I found the Sun Valley at the link below but still can't find the German one.  The wiring diagrams that I have seen always leave #3 fuse blank for options so they are no help. I would like to know which is correct as well.

Did you get it from here: http://www.sl113.org/wiki/Automatic/Start

If so, please tell us what's wrong with that description so that we can make it accurate!

Peter

[wwheeler]

Ben,

When I tested my venturi switch, I disconnected the two wires going to the switch and used continuity to see when the switch was open (no continuity) or closed (continuity). I then simply open the throttle and can tell precisely when the switch opens and closes with the throttle linkage. More of a pain but decisive.

[Ben]

Ben,

When I tested my venturi switch, I disconnected the two wires going to the switch and used continuity to see when the switch was open (no continuity) or closed (continuity). I then simply open the throttle and can tell precisely when the switch opens and closes with the throttle linkage. More of a pain but decisive.

......yes I should try it that way, more decisive indeed.

Bob I wasn't working on the car, never had to. I had been driving it almost daily for months with no issue. I had a long journey to do (350 miles) and the weather looked good so I set off. However the very first gearchange spelled trouble as it lurched like never before. I wasn't sure whether it was my imagination of I had side stepped the throttle or whatever. anyway I continued and straight out onto the motorway where I used plenty of throttle so it never gave me cause for concern. However later in the journey where there was a lot of slow driving it was clear there was a problem.

Hopefully I didn't damage anything by driving back home. The fact that it performs correctly when the kickdown is switched hopefully indicates that the fault is external rather than internal. Hopefully !

[Ben]

So I decided to check the switch out again, since its the easiest option. I removed it and opened it up to find it was full of oil, blowback obviously, and there were lumps of old carbonised gunge stuck inside preventing the contacts from.......ehh contacting !

Actually I think the crap inside was what was preventing me from getting the full range of adjustment. I am not, however, competely sure that this will solve my problem but it didn't hurt to clean it up.

So I will put it back together and check it out or go for a drive. After that I may look at the modulator valve, there is no wire seal on it so somebody was there before and i have one from another tranny which does have the seal so I may swop them over.

Fingers crossed !

[Ben]

SUCCESS !!

Just to finalise, having cleaned the switch and refitted, then adjusted it, I was able to get the solenoid to work correctly.Once the ignition comes on and the car is in gear I hear it click back, as the throttle is cracked open it releases to its middle positions and at kickdown moves to the correct position.

The car drives perfectly with no slippage, though I did notice an un-required gearchange, i.e it changed back to second from third when it shouldn't have, but that was the only time. I then re-checked the oil level and it was very low so I coirrected that and the shifts all appear correct.

So thanks you to all who made suggestions, I really didn't think a small switch would cause the trans to give the trouble it did. It just shows you to check the easiest things first !   

[hands_aus]

Hey Ben,
Good to see you on here again.
Often wonder how you are going.

If you took pics of the inside of the throttle switch could you please post them on this thread.

Bob Smith

[Ben]

Thanks Bob, I have lurked for a long time, but having stripped my car to a shell for restoration, moved house, suffered some health problems, put things on hold, blah blah blah ( insert lots of boring stuff) things are much better now !

I've been using my 280SE Coupe W111 regularly but my W113 is finally getting some attention.

Unfortunately I didn't take any photos sorry. It comes apart easily, no tricks, basically 3 screws and you will find essentially a little bearing and a cap which fits the throttle shaft.One of the contacts is stationary and the other is fitted to a spring which rotates with the shaft.

Thats pretty much it. Mine had dirt, goop and all sorts inside. I should have photo'd sorry................

How's life down your way ?

[waqas]

Hi Ben,

Good to hear that things are getting better now, and glad that you're back!

As a fellow w111 & w113 owner, I too wondered where you'd gone off to. There are now a handful of us w111 owners sneaking our questions here in broad daylight

Keep on posting!

[wwheeler]

I am afraid my results are not as promising as Ben's. My kickdown and venturi switches are new, work and are adjusted properly. I receive the switch "signal" at the trans wire terminal. The solenoid linkage is free, but I still only get a very erratic response from the solenoid and it is weak at best. Neither kickdown nor the idle position work consistently.

Before I contemplate replacing the 3 position solenoid, I thought I might wire the solenoid directly to a power source. Question is which lead is + and which is -? My guess is the switch leads are + and the common solenoid lead is -. Sound correct?

One final question - do you have to remove the trans to replace the solenoid?

It is true that us w111 guys do lurk about the forum. But who can resist the world's best forum! Eventhough I am full member here, I do limit my questions to items that are in common with 113s.

[ja17]

Hello Wallace,

Make sure your charging system is up to specs.  A drop in voltage makes a big difference in the strength of the solenoid. Your car will be pumping out more voltage when it is running also. If your charging system borderline, this may explaine the inconsistant behaviour.  Try changing the battery then taking it for a test drive.

They say it can be done, (replacing the solenoid with tranny in place) but I have never had to do it.

You may want to loosen up the turnbuckle on the trans linkage rod and try to see if changing the length improves the situation. Take a measurement first so you can return it if needed. 

Your quite welcome here Wallace, lets just say you have a five passenger Pagoda!

[wwheeler]

Thanks for the thoughts Joe. I hadn't thought low voltage playing into this. I have a pulse charger that works well and will charge the battery fully, measure the voltage and try the solenoid again. What should the voltage be at the terminal connection? I'll look at the turnbuckle too as you suggested.

I had an original throttle solenoid when I bought the car. It would barely move and didn't have the oomph to reposition the throttle linkage when put into drive. I replaced it ($$ouch!) and works great now. Logic tells you that a solenoid should either work or not. I wonder if maybe there is some dirt or grunge in the solenoid reducing its strength?   

[hands_aus]

Hey Ben,
it is good to know you are back on track.
In the 280SE coupe you have a lovely alternative to the Pagoda.

Life here is like everywhere suffering from the recession.
Luckily in Brisbane we have had some rain to top up our dams and we are heading into one of our beautiful winters of warm bluesky days and cold nights.
 
At the moment my Pagoda is having a new timing chain and tensioner fitted and rockers/valves adjusted.
The original chain was replaced in 1977 at 93K miles when the engine was overhauled (from original service manual).

I lurk and contribute when I can. I always read every post no matter the topic.

welcome back mate.

[wwheeler]

I have attached two wiring diagrams for the wiring to the 3 position solenoid. One is familiar and in the tech manual. The other is in German and I can not remember where I found it.

The one in English has the schematic that I also found in Glenn's Mercedes Benz repair and tune-up guide. In the guide, the symbols are much clearer. My question is, which one is correct? If I am interpreting the English one correctly, the kickdown switch (#4) and the throttle body switch (#3) are grounded switches (the ground symbol is clearer in the book) and the solenoid gets its power from #3 fuse with the largest wire terminal. 

In contrast, the German schematic has kickdown and throttle switch (#55 and 52 respectfully) coming off the #3 fuse and then to the solenoid. In this schematic, the large wire is the ground going to the solenoid. This is exactly opposite the English version.

My '68 280 SE 111 has the same wiring as the German version and I checked it twice to be sure. The title of this document is originally meant for '68 280 SL W113. So are some years wired differently than others? If some one has the definitive answer, I think it would be good to update the tech manual. 

[Peter van Es]

Before we update the Tech Manual, I'd like some confirmation on what is correct -- I'm no expert. The German document you've included has a big disclaimer at the top saying in effect that "Your car may be wired differently. Especially with Export models (for the USA) this is likely to be the case".

Peter

[wwheeler]

I still cannot get my 3 position trans solenoid to work reliably. The kickdown position works all of the time but the idle position works only about 50% of the time.

I have been testing the entire solenoid circuit and it always comes back to the throttle switch. I replaced the throttle switch several months ago with a new MB part when I rebuilt my venturi unit. I have since taken it apart a couple of times and cleaned the points. It always works 100% of the time for a while but slowly gets worse until it then only works part of the time. I found my old throttle switch and put it on and now the solenoid works everytime in both positions.

Problem is that I would really like to the use the new switch. Is there a preferred method for cleaning the points? I remember reading a thread about some new MB relays that wouldn't work until the points were cleaned. This sounds a bit like my situation.

Any thoughts?