The car will not start. Here are the diagnostic things done so far:

Will not crank - with lights on trying to crank will not dim lights.

Probed terminal wire on firewall to left of brake reservior - no juice to middle wire when cranking.

Disconnected cable to NSS and jumped terminals #81 and #50 on cable; when ingnition switch moved to ON position (not start) starter engages and continues to run. Car starts but starter running.

Hope someone can help diagnose .. seems like ignition switch, not NSS or is this an alarm relay problem and if so what's the fix??

Thanks in advance for any/all help

Cheers

Jumpering wrong terminals on NSS
N and P jumper is #50 and 50R--- not 81
You are tapping into back-up lamp circuit..

I would look at the alarm interupt relay, K38 I think.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

K38 would be another suspect , but you want to jumper the NNS first.
The K38 circuit can be jumpered at its relay terminal 3 and 1 , but it is much easier/faster to just check for power at terminal 50 of NSS with the key turned to Start position.
12 V test lamp here indicates AT circuit [ K38 ] OK...
The power chain is Ign sw -to K38- to NSS - to starter sol.
To make it easy all around . if one checks the center wire on the firewall
as you have done , that is the starter sol end of the circuit . The other end is the NSS , ..so your jumper is the correct next step. .. but you just have the wrong jumper terminals and are feeding the starter circuit through the Back Lamp contacts of the sw.
That is why your starter keeps turning.
If no 12 v at 50 of NSS, than ign/sw or K38 are suspect....

Thanks Arthur .. did jump #50 - #50R (on my cable only 3 terminals are numbered .. 81, 81a and 50, so I assume 50r is the unnumbered one) .. no joy on starting, but did not check power to 50, which I will do next .. if no power, what is the diagnosis, fix?

Thanks Again

Tim

ok
80/81a are the back up lamp circuit.. different contacts/circuit , as this is a dual circuit switch..

So, the feed from the ign/k38 go to feed 50 at NSS .. from there, power goes to 50r when in N or P [ through NSS contacts] and that feeds that center terminal I mentioned on firewall.
[ PS . for anyone ..the firewall terminal is another easy to get to test point for checking the starter/solinoid ... if one just brings a wire from bat + to this terminal. the starter will turn. This is a good test circuit break-point for diagnosis as it eliminate all interior switches and wireing by getting direct feed to starter , saving the Tech muchooo time decideing starter part of circuit or NSS/K38 circuit.. there are a few of these terminal spots that are easily gotten to without tearing stuff apart . this is where schematics are priceless and the Best Feature of the CDs... ]

If power at 50 and none at firewall.. has to be NSS
If no power at 50 , has to be K38 or ign sw not feeding NSS at50

Just remember there will be NO power at test lamp until you turn key to start
position... [ making sure you have tranny in Park when doing ANY starter circuit test]
I assume you are jumping the wire connector ends and NOT the terminals at the NSS....

Thanks Again Arthur ..

Had made a little jumper wire and jumped 50 - 50r before with no luck (yes working on cable, not the switch on the tranny ) so expected no power at 50 ... did just go and check and yes, no power at 50 when engaging the starter with the key ..

so how does one trouble shoot the alarm relay and ing sw???

also, altho I am sure it is not related, one of the relays behind the fuse box buzzes softly when the key is on (not the annoying ign buzzer, it's the flasher et al relay)

the alarm doesn't seem to work, I locked the car (from passenger side) with the drivers window down and opened the driver door from the inside .. got one little 'beep' , no headlight flash ..

again, the help is REALLY appreciated!!!!!!

Tim

Do you have blinking red led at console when Arming car?
When looking for power at 50, you went from 50 to ground, correct??

Looks like K38 problems if no alarm

K38 is behind the dash cluster . upper/left section.. approx behind gas gage location...
Terminals to test/jump on that relay will be 3 and 1.. via schematic

Relay #s will be 30 for terminal 3 and 87 for terminal #1.
Those are circuit # on the actual relay..

Again thanks Arthur ..

Sorry for the delay in response .. fun with my cr-- ISP Adelphia

When looking for power at 50, went from 50 to ground as assistant held key to start position .. no power .. but I expected this as when I jumped 50-50r got no crank ...

Assuming I can access the alarm relay (just hate pulling that instrument cluster .. have done it several times on previous models and it's just a pain getting at the speedo cable to get the darn thing out!!) When I get it out (project for another day) I think what you are suggesting is jumping terminals #1 & #3 at the relay mount (not the relay itself of course) and seeing if I get start??

As for the alarm .. have never seen an LED lit on this car (wife's car she bought used) .. know it is supposed to be on the center console near the headrest switch somewhere, but I have never seen it flashing ... as mentioned I think if it was working (alarm) when I lock from passenger door and open locked door on drivers side (by reaching inside and using inside handle) the alarm would go off .. got a weak beep, no lights flash and that's it.

I can't say thanks enough!!!!

Tim

got to thinking (dangerous I know) .. went out sat in the car with the window down (passenger side) .. reached out and locked the door and WOW there is this really dim little LED on the dash .. blink blink .. can't see it unless you are really close, but there it is .. opened the door from the inside and after a brief delay the lights indeed started flashing along with a relay noise from under the passenger dash .. from this I am assuming the alarm and it's relay are OK?? .. perhaps the alarm horn is not working or if it used the car horn those are disconnected ..

Following these thoughts that leaves the ign sw .. funny .. about 9 - 12 mos ago she had this sw replaced by an idie shop that charged her $500 (was not locked, switch turned and could move steering and shift in unlocked postion)

Anyway be interested in your take ..

Thanks

Tim

OK

Yess , the led is very dim.. it is easiest seen in the dark through the rear window .
So, from your last post, I believe yu have a bad contactor set on the K38.
When the led is on , the relay pulls the contacts to the Armed circuit, but the are the same contact that interupts the starter power from the ign sw. So, you can not start the car ..
I have the schematic up [ sorry I can't send it b/c my scanner has been sent to Fl.. I am in a moving process] maybe someone can post it and I can walk you throught it..

Anyway.. here is the wiring.. just draw it from this and you will see whats supposed to happen.

Red+ goes to ign sw...this is BAT power for all ign sw.
Start position of ign sw is term 50.. this is large Violet wire
This V wire goes to K38, term 1 [87 0n relay]
When alarm is not activated, the power from #1 comes out of K38 relay at term 3.. this is V/Gn wire. [ note on schematic .. these two wires are jumpered on Canadian models , ie/no alarm disable] ..these are the contacts I suspect in the relay and that is why I mentioned jumping here for K38 contact test.. 1 & 3 jumper will eliminate the K38 circuit/relay starter interupt.
This #3 V/gn wire coming out of K38 now continues on to term 50 at NSS
[ I am sure you see where we are going now] That is why we looked at NSS/50 for power.
Coming out of NSS at 50R is V/Wt which goes to the terminal board at the firewall, center term...[ which you already know]...and from there down to the starter sol

Hell of a way to get a schematic to ya .. but if you just draw that out from
beginning to end , you will have it. Just draw 4 boxes and connect them as I printed
ign box.....K38 box....Nss box.....starterbox
Thats the sequence , now just run a connecting wire from ign right through to starter , using the terminals I mention on each, in and out ..
It is just a simple Series circuit that has to go through a few saftey/alarm contacts to get from the ign sw to the starter solinoid. You just have the fun of finding out which one doesn't like you.

Thanks Arthur .. will make the dwg .. have it pictured mentally now ..

How hard is it to access the electrical portion of the ign sw?? seems like the simplest test now is just to jumper across 1 and 3 of the alarm relay mount and try starting? am I on the right track?

Also where in FL is the move? .. I am in FL in the Port Saint Lucie/Stuart area and would love to buy you a couple if the opportunity presents itself ..

Thanks is so inadequate, but thanks ..

Cheers

Tim

Cool..
The best bet is to just get to the K38. You can look for voltage at pin #1 once you are there and that will verify Ign sw feed to that point,,,easier than taking out ign sw. Same deal as with NSS/#50 12v. lamp test.. with Ign.Sw in Start position...if you get power in K38, but none out ... you know that is the problem

The jumper is just a faster way b/c you don't have to do voltage testings ..but you can , if you like ..either way.

I own a Home in the Ocala area and will be making it full time . Might see you down there..
Good Luck and let us know what the fault outcome was.....

Will do .. try to test in the next couple days and will let all know the outcome .. should be easy to see .. power to pin 1 ign sw OK .. no power ign sw is the problem ..

will post as soon as I know ...

Again .. thanks!!!!!!!!!!!!!!!!!!!!!!!!!!!

Tim

Arthur, I don't know how you knew it was the alarm relay and not the ign switch, but sure enough .. checked an had power to term #1 and if I jump 1 and 3 starts right up .. have the relay jumped for now and will get a new one ASAP (assume it is P2020-25016) ...

Sure is wonderful to have folks like yourself and others on this forum, having owned many MB's over a long period have accumulated some knowlege I will try to contribute, but my knowlege is mostly mechanical, while I understand elec, just not much experience .. your experience and know-how have been invaluable!!!!

Cheers

Tim