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1994 E320 Sedan
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611 Posts
I've learned a trick that seems to stop my alarm from going off when unlocking from the trunk. It looks as though the door locks become slower to unlock as the weather gets colder. I've discovered that if I open the trunk before all the locks are up, the alarm goes off. If I wait for all the locks to come up, no alarm. When it's after dusk, I can usually look at the alarm light on the center console, but if it's bright out, I watch the locks.
 

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'95 S320
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7 Posts
Found K38 relay on '95 S320

i ripped apart my inst cluster and this relay was not avail... also my cover on the floor was a bit different... no idea where this relay may be.. looked all over no wires of that color even ....:surrender:
I located K38 relay hidden in the back of the main fuse box. I had given up on looking for relay and was just going to run wires to starter/solenoid when I found relay in rear of fuse box. I had no luck jumping the wires on the relay, starter still doesn't crank. I ran wires to a push switch to activate starter. I did this after discovering I could start car with screwdriver by touching the hot lead on starter and the smaller lead on solenoid.
 

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Buncha W124's
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2,086 Posts
I located K38 relay hidden in the back of the main fuse box. I had given up on looking for relay and was just going to run wires to starter/solenoid when I found relay in rear of fuse box. I had no luck jumping the wires on the relay, starter still doesn't crank. I ran wires to a push switch to activate starter. I did this after discovering I could start car with screwdriver by touching the hot lead on starter and the smaller lead on solenoid.
Uh, I'm not sure if that is K38. Are you only experiencing the no-start problem when the alarm is disconnected, and the starter works normally if you re-connect the alarm modules?

:confused:
 

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'95 S320
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7 Posts
Uh, I'm not sure if that is K38. Are you only experiencing the no-start problem when the alarm is disconnected, and the starter works normally if you re-connect the alarm modules?

:confused:
It doesn't seem to matter if the alarm module is connected or not. It may be related to the failure of the central locking system too. A few weeks ago the alarm went off when I opened the passenger door. I put the key in the ignition and it started car with alarm and lights flashing. I disconnected negative battery terminal and the next morning I went to start car but starter was unresponsive. Prior to total failure, I noticed that if the rear trunk were slammed shut the starter would crank. I know there is an ignition lock out in the trunk key position so it could be related to the trunk key switch too?
I found that jumping the starter wire & starter solenoid I could start the car. I ran two wires from starter up through the fuse box to interior of car and this is how I came across the relays in the rear of the fuse box. Car starts well with new push button(momentary) switch. Now it has a push button start.
 

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1990 300E
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746 Posts
I just witnessed the failed alarm so I'll be watching this thread closely. Did it piss my wife off something fierce.......ooh boy........
 

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1993 300TE 4Matic, White with Blue Interior
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1 Posts
Fantastic post, thank you very much.

I had an issue with my 93 300TE where I tried to disconnect the alarm, but in doing so the alarm connector came apart and I couldn't figure out what order the wires go back in (even after trying to find a pinout diagram online). So I resorted to bypassing the whole alarm system with the instructions in this post, and now the car starts again!

However, now the power locks are not working. I also had a new stereo installed, so it could be related to that... but has any else had this power locks issue? I'm back to the old days where you have to manually lock each door, it's awful!

Any help would be greatly appreciated.
 

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1987 420 SEL
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104 Posts
Immobilizer

These older post are always helpful. Thanks to all who provided information on disabling the alarm system.
I agree the post is as relevant today (and I do mean TODAY) as it was when posted.

In my case the immobilizer appears to randomly engage and disengage. In other words, intermittent no start conditions, and no rhyme or reason for when the alarm will sound (that I can figure out). And twice the car stalled or failed to start while I was in the middle of the street. Such stress.
 

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87 w124 AMG, 87 W201, 94 w202, 99 w210
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173 Posts
heyguys, i became kind of fluent with these symptoms of the alarm randomly going off. in all 3 of my cases with this issue on the W124 w201 and w202, it has been a bad wiring harness chipping away exposing wires, disabling the alarm is only a temp fix, there are bigger issues at steak...
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,229 Posts
I recently disabled the alarm in my 94 E320, which has the starter lockout relay (found on 1993+ ATA systems). not wanting to deal with pulling the dashboard to access the starter relay, I carefully studied the ETM, and determined that I could jumper pin 1 to pin 2 on the larger connector at the ATA alarm box under the passenger floor board, and that will enable the starter relay..
 

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1987 420 SEL
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104 Posts
Nice work to jump anti theft system

I recently disabled the alarm in my 94 E320, which has the starter lockout relay (found on 1993+ ATA systems). not wanting to deal with pulling the dashboard to access the starter relay, I carefully studied the ETM, and determined that I could jumper pin 1 to pin 2 on the larger connector at the ATA alarm box under the passenger floor board, and that will enable the starter relay..
Is that what the "immobilizer" does? Disables the starter? Or something else? My engine cranks like crazy and I'm blaming the anti-theft for the problem, but I'm thinking perhaps the fuel relay.
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,229 Posts
yup, thats ALL the immobilizer does, disable the starter motor. the starter signal on the ignition switch goes through that relay en route to the starter solenoid.

here's the wiring diagram of the ATA (Antitheft alarm) on a 1994-95 E320 wagon
https://www.startekinfo.com/StarTek/outside/12264/Program/ETM/2482400.pdf

relay K38 is the immobilizer relay, located on the firewall behind the instrument panel. N26 is the ATA module itself, located under the passenger foot panel, and M1 is the starter motor.

note that N26 connector 1 pin 1 goes to the immobilizer relay coil K38 pin 5, the other side of said coil, K38 pin 4 is connected to fuse 5 and on to power circuit 15 (on with ignition or start). ignition switch S2/1 pin '50' (start) goes to relay K38 pin 1, and relay K38 pin 3 goes to the park/neutral safety switch S16/1 pin 8, P/N switch pin 9 goes to the starter switch.

so yeah, if your starter turns over, your problem is NOT the immobilizer.
 

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1987 420 SEL
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104 Posts
yup, thats ALL the immobilizer does, disable the starter motor. the starter signal on the ignition switch goes through that relay en route to the starter solenoid.

here's the wiring diagram of the ATA (Antitheft alarm) on a 1994-95 E320 wagon
https://www.startekinfo.com/StarTek/outside/12264/Program/ETM/2482400.pdf

relay K38 is the immobilizer relay, located on the firewall behind the instrument panel. N26 is the ATA module itself, located under the passenger foot panel, and M1 is the starter motor.

note that N26 connector 1 pin 1 goes to the immobilizer relay coil K38 pin 5, the other side of said coil, K38 pin 4 is connected to fuse 5 and on to power circuit 15 (on with ignition or start). ignition switch S2/1 pin '50' (start) goes to relay K38 pin 1, and relay K38 pin 3 goes to the park/neutral safety switch S16/1 pin 8, P/N switch pin 9 goes to the starter switch.

so yeah, if your starter turns over, your problem is NOT the immobilizer.
Understood. Thank you.
Frustratingly, the car started right up this morning after sitting overnight. My brother, who is not a mechanic, guesses that eventually the anti-theft system timed out and reset itself, which is why the car started up. But if the ATA is the immobilizer, which disengages the starter, then that can't be the answer.

With respect to disabling the alarm which is posted in this thread, I am including here a photo of the same module (identical twin multi-pin connectors) which is under the passenger foot rest of my 1992 400E:
https://plus.google.com/u/1/photos?pid=5989903311691537938&oid=113683761986407393197
So the module which is previously identified as the anti-theft alarm clearly has "Becker Audio" on the sticker in my car, which leads me to believe it's part of the stereo amplifier system. Unless Becker Audio also made the ATA component.
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,229 Posts
can't se your photo, but my ATA is made by Becker. The one from my 1994 E320 is 124 820 56 26 [09]
 

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2005 E55
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786 Posts
I recently disabled the alarm in my 94 E320, which has the starter lockout relay (found on 1993+ ATA systems). not wanting to deal with pulling the dashboard to access the starter relay, I carefully studied the ETM, and determined that I could jumper pin 1 to pin 2 on the larger connector at the ATA alarm box under the passenger floor board, and that will enable the starter relay..
This works to a T!

Thank you very much! :smile
 

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1992 300E 2.6
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359 Posts
"Step 3: Unplug those big plugs. On pre 1993 cars, this should be sufficient to disable the car. Not the case though for 1993+ cars as they have an immobilizer feature that is triggered when the alarm is disabled. so my car would not start after unplugging those two plugs."

I need to do this on a '92 ; so hopefully I can stop at Step 3. Anybody else done this on a pre 1993 W124 before and it worked?
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,229 Posts
i disabled the alarm on a 1990 as well as a 94.

if your car has the immobilizer, the starter simply won't crank after unplugging the ATA, and the simplest fix is to jumper two pins on one of the plugs you just unplugged as I posted months ago...
 

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1992 300E 2.6
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359 Posts
I have a 1992 W124 and I unplugged those 2 plugs under the passg floorboard as in Step 3 and my parking lights still flash when opening the door or while driving or when stepping on the brakes (they go off and on). Anybody know how could resolve this?
 

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1990 Benz 300E 2.6 (mine) ; 1994 E320 Wagon (wife's) ; 1993 300CE Cabrio, needs some TLC
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7,229 Posts
my parking lights don't flash at all when the alarm is armed/disarmed. Did someone add an aftermarket alarm remote system to this car?
 

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1992 300E 2.6
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359 Posts
my parking lights don't flash at all when the alarm is armed/disarmed. Did someone add an aftermarket alarm remote system to this car?
Yea unfortunately, it was on there when I bought it. Can you or somebody help me resolve this? :confused:
 
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