How Do I Test the Neutral Safety Switch?

[ejsharp]

This request is somewhat urgent. Our 190E won't start. It must be the solinoid or the neutral safety switch that is causing the problem. Car has been down for almost a week and we need it for wife to go to work.

Can someone tell me how to test the system to determine what part is defective? The starter will not engage and I tried to start in neutral and in park. Battery is very good.

Things are very tight in the 190. I cannot see much on the driver's side of trans and starter is almost inaccessable.

Any help from an experienced tech would be most appriciated.

Thanks.

[kramlavud]

I had the same problem a few months back; and Arthur Dalton showed me how to test the neutral safety swithc from the emgine compartment. Open the link following this paragraph, and scroll to the 4th post on the 2nd page. My engine started when I applied battery voltage to the switch as directed by Arthur, thus my NSS was at fault. Had a new one installed and the problem was solved.

http://www.peachparts.com/shopforum/sh...+safety+switch

regards,
Mark

p.s. this worked on my 94 E320
MD

[ejsharp]

Mark,

Thank you for that wealth of information. I tried to link to the thread you listed but the server won't let me through to it. I'll try an alternative search on either you or Dalton to see if I can get to it.

Your reply really takes a lot of pressure off me.

Again many, many thanks.

[kramlavud]

Here is the text:

"OK . I want to make sure you are the right connector/plug.. it is a 3 prong , all in a row connector held to the wall (kramlavud adds:this is the wall between the engine compartment and the the firewall) with 2 screws .the V/WT is the center connector...... maybe your light is out or you had not pierced the wire fully... test your light by leaving the red on the ring and go to the bat + to test lights integrity..

Here is another prof positive test that will test the same point , but in a different way..(kramlavud adds: I used this method to determine my NNS was at fault)
Get a jumper wire and hook one end to the bat + ...
Now, unplug the connector at booster and I want you to look at the 3 MALE connectors at the part of the connector that is screwed to the wall..[not the part you unplugged w/ female connectors]
Take your bat + wire and touch the CENTER MALE connector .. the starter should crank the engine ..if not , you have a problem at the starter or wire going from this connector to the starter.. if the starter turns the engine over [ cranks] w/test, the starter/sol are verified as GOOD. This means you are not getting power at the wall 3 prong connector and the problem is in the NSS circuit..
The reason for testing at this point/connector is that it is a place in the circuit that is easily accessed and it is the dividing point [ electrically] between the NSS circuit and the starter/sol circuit
I think you follow me...."

Hope this helps.
Mark

[meangrean]

One quick way of checking if the starter works on that car is on the right side of the Brake booster in a circular conector.if you unplug it and put + on the female connector (i believe) make sure it is the one going down to the engine and not to the mail wiring haress.If you put positive on that wire the starter will turn over if goodOr if you dont want to try and do it ,use the connector that does go to the firewall or main harness and but a volt meter to it and have someone try and start the car.You should get battery voltage while it is being cranked

[John M Cacavas]

If it becomes necessary to change the neutral safety switch, I took the time last year to document the process and put it on my web page.

Go to http://cacavas.com and follow the Mercedes link and you'll see how I did it, and other details as to how to do it.

John Cacavas
Los Angeles.

[bhatt]

The NSS is just a simple open/close switch. If you disconnect it (I think there is a connector nearby) and jump the two terminals, you have bypassed the switch.

If the car starts with the jumper across the switch, it's bad.

Keep in mind that many switches die and prevent the car from starting ONLY in Park (they will start just fine in Neutral) BUT mine didn't do this. It wouldn't start in Neutral either. I entirely overlooked the NSS because I thought that wasn't the problem (since the car didn't start in Neutral either).

NOTE: Do NOT leave the switch jumpered for any period of time. Wouldn't want your wife or any one else starting the car while it's in Drive and running over/into something or someone! If the switch is bad, order the new part ASAP and make sure you are the ONLY one who drives the car.. hide any other keys to the car for a few days.. it won't hurt!

Neal

[ejsharp]

Thank you, thank you, thank you. You guys are the greatest. The Mohammed Ali's of Mercedes.com.

I am on my way out now to check out the car. Will keep you posted.

[ejsharp]

Ok... I did the tests. The round connector to the right of the brake booster is not the right one. It goes to the brakes under the fender well. The switch we want is the round one to the left of the brake booster.

I put battery voltage to the male end and got voltage to the solinoid but solinoid and starter would not operate. I then took a couple 3/8" extension bars put them together and sliped then down past the oil filter (from under the hood) and tapped on the starter while I had the male end of the connector jumped to battery voltage.

The solinoid and starter then activated and turned the engine over. The solinoid is evidently stuck for some reason.

So it looks like I have a bad solinoid. Is there a way to repair the solinoid? Can it be purchased separate from starter?

Again thanks to all who helped out so far.

[bhatt]

If your starter is original, I've always believed it is best to replace both. If the solenoid is dead, you can probably replace it but is the starter that far behind? Why remove an old part from the car, swap one piece of it, then put it back on?

I'd personally buy a good rebuilt starter (Bosch) and replace the whole thing. You should be OK without risk of being stranded for many, many years.

Anyone else, please feel free to disagree with me.. that's just my personal opinion. I treat these parts like headlight bulbs - you can replace one but the other is just as old! I can't tell you how many times I've replaced two bulbs a week apart

Neal

[ejsharp]

I'll pull the starter tomorrow and have a look at it. Sometimes they are fixable.

If not I'll do the Bosch rebuilt and return the core. Too bad Fast Lane does not take cores because their price is double that of local parts stores. Would be impractical to ship core because of weight I suppose.
Does anyone know if you can get to that second starter bolt using an extended extension rod and from behind the transmission? The bolt is inexcessable at the starter itself.

[bhatt]

On the 560SL my wife used to have, I did exactly that -- used a long extension bar.

I recall it was either 18" or 24" long. I bought a set of three from Harbor Freight that had one which was perfect. You can't go wrong with a 18" or 24" extension and a couple of universal joints. I recall someone telling me you CANNOT get those bolts out without that extension.

Once I had the extensions and universal joints, the job was really ease. Be REALLY careful to not drop the starter on any body parts.. it's heavy! I'd make sure to be clear of it, just in case you end up dropping it when the last bolt is pulled out. Might want to have something for it to land on (plywood, foam, etc.) rather than having it hit asphalt or concrete if you're returning the core.

Neal

[ejsharp]

Neal,
I looked at the situation under the car and it appears as though the top bolt cannot be reached from there. I think the starter is mounted too high on the 190 2.3 engine.

Maybe the air breather, oil filter and whatever else in covering the starter has to be removed to get to the top bolt.

If anybody knows the answer to the question: Do you access the top bolt from under the hood?... please reply. If so I can probably figure out what parts must be removed in order to get to it.

Any replies will be most appriciated because it is a must that I get this car back on the road.

[bhatt]

Earl,

Looked your car up quickly in WIS and it says the following pre-work needs to be done before removing the starter:

-Air cleaner removed (09-0400) with GF starter motor, 601, 602.911 with Auto Trans and/or A/C up to model year 1990
-Engine compartment lining removed (61-0105), engines 102, 103
-Noise capsule removed (94-0050), engines 601, 602
-Control arm (left) on pitman arm removed (46-0550), engines 102(with GF starter motor), 103, 602.911, 602.961

So it appears the Air Cleaner is only removed on diesel models. However, looks like you need to remove the engine compartment lining, and the control arm/pitman arm.

The document numbers in brackets are from WIS. Let me know if you need any of them and I can scan & email (really tough.. tried it once) or FAX them (this is the easiest way.. I can print & fax much faster than scanning it!)

The instructions to remove the starter are quite standard with a few exceptions. The document says to remove:
-Intake pipe support
-Return spring between throttle & intake pipe support
-Adjusting element (don't know what this is..)
-from there, it's standard.. remove electrical connections & bolts, remove & reinstall starter.

I have a document with pictures called "Removal & Installation of Starter Motor Model 201" which contains all of these instructions & diagrams. Let me know if you need it.

Sounds like a bunch of simple removal work (not sure about that Pitman arm though!) and then the starter comes out. You may be right about removing stuff from above (air cleaner, etc.) on your model!

Disclaimer -- this is the MB way to do it (which is usually right). Someone else may have already done this work and know a shortcut around it. Does anyone else know a workaround for that Pitman arm thing? Is that really necessary?

Neal

[ejsharp]

Neal,
Been working on it all day and I just got it out around 5:00 this evening.

Actually you have to work from the top and bottom on the 93 model, 2.3 190E.

The mounting bracket is scarry because it looks like it would be stuck in there but its not. It moves once unbolted. Getting to the bottom bolt of the bracket is a challenge. I used 3/8 extension and went in from the side of the intake manifold near fender. Top bolts of bracket sit just under the air breather cover and are 6mm hex.

The pitman arm does not have to be removed. You get it out of the way by turning the steering wheel.. to the right, I believe.

Top starter bolt is removed from under the hood and bottom starter bolt from under the car.

I removed starter wires after unbolting starter and by removing the bolt to the fastener that adjust the length of the cable going to the starter. Loosening the cable lets you turn and drop the starter somewhat so that you can get to the nut and phillips head screw that fasten the wires to the solinoid and starter.

The starter then slides out through the bottom past the pitman arm.

I tested the unit one I got it out and so far it works fine. I suspect that the contact point at the solinoid and wire leading to it is coroded and that is why starter failed to activate.

I put starter in freezer to see if the solinoid will stick during next test.

Hope wife does not take it out and cook it for dinner.

Earl

P.S. I did do the neutral safety switch test prior to removal of starter and the switch passed. I ran voltage directly to solinoid from firewall and got no activity from solinoid. I then tapped on the starter and it activated.

So it could be the contact point between wire and solinoid that is corroded... or it could be a stuck solinoid piston. Maybe the freezer test will tell me something.

Does anyone have any experience as to corrosion causing a failure as described above.

Neal, thanks again for going the extra mile.