View Full Version : central locking switch

01-24-2013, 04:05 PM
I had the dash apart and when re-plugging the switches, I mixed thing up. I plugged the CL switch into the wrong plug and activated the switch. When all switches are plugged (correctly) the CL switch only lights, no lock operation. All other locking functions work ie. remote, lock on start etc. There were no error codes on CTM diagnostics. Semi dis-assembling the switch, I noticed what appears to be diodes, besides LEDs. Would anyone offer a guess or any other troubleshooting ideas? I'm inclined to go with the switch being blown. Thanks for any ideas. This an 04, 2500 HT :thinking:

01-24-2013, 09:08 PM
I'd start by simply ohmmetering the switch (although, if you've taken it apart, you may have damaged the switch)

The two switch contacts merely bring their respective pins to ground, and the diodes serve to prevent "back flow" of the indicator light currents to other devices on that battery feed (since the lock lights operate with the vehicle off)

Here is/are the switch internals:

(from both the 2003 and 2006 service manuals, available here: http://aie-services-2.net/Sprinter/ )

added: the central timing module requires that "fuse 5 (25 amps)" in fuse block 2 (the side of the driver's seat pedestal) be happy.
That's the fuse that actually powers the door locks.


01-25-2013, 01:56 AM
I tried ringing out the switch as you suggested. I think the internal diodes are fried from the improper voltage polarity. When I get the switch fully open, I'll try and post a pic. MB is proud of this switch for $ 44. The dealer should have one tomorrow for me and I'll follow up the results. Thanks for sharing the schematics with me. Bill

01-25-2013, 02:45 AM
re-reading your original post, plus looking at the schematic, the two diodes on the left are merely the "illuminate the switch at night" lights, (i'd missed that they were LEDs),
and the other two are the tally triangles. No sneaky current-flow blocking.
Thus they shouldn't prevent the switch from working (in terms of locks cycling), unless you'd somehow fried the switch contacts themselves (difficult, and you'd probably feel the difference as you pressed it).
I'd guess that the other components you saw inside were current-limiting resistors, to keep the flow through the "at night" LEDs down to 20 milliamps or less.
Thus they'd be roughly 600 ohms or so.

Hopefully a new switch will fix it (what socket did you mistakenly plug it into?)

good luck

01-25-2013, 05:53 PM
The new switch cured the problem. I have not completely opened the old one yet. I had plugged the plug for the ARS switch into the Central locking. The ARS switch wasn't damaged. The next time I go in, I'll put numbers on both haves of the plug. Thanks again for your help and illustrations. I'll get with a pic to share. Bill

01-27-2013, 02:37 AM
Just a note about the switch's other effects. When the switch was "bad", the "key in ignition" chime would only sound after key was moved to "on" and then back to locked position. With new switch, when the key is ignition and door is open, the chime sounds. except when engine is running. Perhaps the thought will help someone. Bill

07-03-2014, 01:29 AM
Did u ever look into the old switch ? I did the exact same thing....:(

09-05-2016, 02:37 AM
Me too, damn it. Ordering new one tomorrow.