w124 turn-key NOTHING (suspect: faulty security system)
 

Vehicle: 1995 E320 Sedan (California)
Symptoms: Turn key> Nothing>


The red light that indicates that the security system is Active, blinks dim after I lock the doors (so dimly that it cannot be seen in the days light). It stops blinking when I unlock the doors, but starts blinking at full brightness when I turn the key to Accessory+. Turning the key to Start yields no indication that the starter is receiving its 12v signal, the the Security system LED continues to blink with the key turned all the way, until the key is returned to the Off position. The security system is definitely not functioning as it should. I preformed the test (by unlocking both doors on separate occasions - manually with the windows down after locking the car from all key holes) No horn, no flashing headlights, no change. I also tried unlocking the vehicle from all key holes, and still nothing.

It is worth noting that I most recently replaced the Neutral Safety Switch. The vehicle started for me initially after replacing the NSS, then again when I showed my wife that her car finally operated as it should. But it would not crank that evening, not even with some liberal shifter persuasion.


My next move is to disable the security system's immobilization relay behind the cluster. Maybe tap on the starter when my wife gets home, just for peace of mind. Sound about right?





Seemingly Unrelated:
-Replaced the the OVP relay a few weeks ago.
-The central locking pneumatics have not been working for a few weeks.
-The radio antenna has not been working, and resulting in a non working radio for a week.

this should help you disable your alarm: http://www.peachparts.com/shopforum/tech-help/269799-how-disable-alarm-1993-w124.html?highlight=disable+alarm

however, assuming the alarm isn't at fault, I would bypass the nss first .... u insert a jumper cable a little above the gas pedal .... i found the instructions on this site when my nss went bad and car started fine while i waited for my new nss to arrive .... post # 13 here: http://www.peachparts.com/shopforum/tech-help/206029-90-300te-starting-problems.html?highlight=X49 and you don't have to remove the cables like the pic, i found, just put a jumper cable when you unclip the cover to the pictured connector

Thank you for the reply.

I jumped the immobilization relay (as seen in this pic http://i893.photobucket.com/albums/ac140/latief_Q/IMG_3972.jpg) and bingo, the car started, in Park, as it should.

Next order of business, how do I diagnose the actual issue, without throwing money at new relays and security system components?

if disabling the alarm altogether is not an option for you, i would check the car if it has the same relay somewhere else and swap it for a few moments to check it out ... can't remember if there is a same size relay behind the fuse box ...

I would prefer to have a fully functioning security system with the immobilizer in tact. After I installed the jumped relay, and turned the key the alarm started going off. I disarmed it by turning the key in the trunk ( I did not try the door)

I will take a look at that blue relay this afternoon.