demoer

The back door/hatch on my sister's 2003 ML350 seems to have forgotten its locking "position". I have tested the actuator, and it works -- the problem is that when I press "unlock", the actuator locks, and likewise when I press "lock", it "unlocks". The other doors do to correct command, but the hatch does the opposite.

I have replaced the relays and checked the fuse. I don't know the history on the problem (insofar as how this might have been occurring), because my sister can't remember, but there were some various lock/unlock issues with the rear doors and the hatch. One relay (I'm not sure which, because I replaced three) appears to have been faulty, and replacing it fixed the previous issue, which was that not all the doors would unlock when I pressed "unlock".

However, now with new relays, the hatch lock seems to "think" its in the opposite position than it is. Also, the hatch lock does not seem to be recieving the signal from the key fob: when pressed, the marker lights flash, but nothing else happens (it doesn't unlock the hatch). When locking the truck with the key fob, the hatch will unlock, which means that you have to go manually lock the hatch.

I have re-sync'd the key fob and also tried removing single relays at a time, in an attempt to isolate the issue. But so far I haven't had any luck. I can confirm that all the door lock actuators work, in as much as they are all capable of cycling (but the rear actuator cycles the wrong way). Is anyone familiar with this issue?

Again, to summarize:
Press Lock --- All doors lock, but hatch unlocks.
Press Unlock --- All doors unlock, but hatch locks.
Press Hatch button on Key Fob: Marker lights flash, but nothing else happens. I did notice when I had the back door panel off that there is no antenna/amplifier module where there should be one. It seems like a different thing, but could that have anything to do with the signal getting messed up?

Thanks for any help you can offer!

Maj. Dundee

You probably have the wrong make relay in place. Check to see that relay K15 Tailgate Unlock, is Hella brand with #4RD9316802---A002 542 14 19.

demoer

Thank for the idea -- they are the correct relays. I bought them from FCP Euro. I'm running in circles figuring this out. I have (accidentally) figured out a way to make the hatch just not respond at all, so at least it saves the trouble of remembering to lock the hatch after locking the doors. I might have to just leave it at that until I accidentally figure out how to make it work correctly! There are just so many permutations to run through.

Maj. Dundee

The whole problem lies with the fact that you do not remember what relays you replaced.

Did you ever mess around with the tailgate lock?

Relay #15 controls the unlocking of the tailgate. Relay #17 controls the front wipers.

Remove both relays and insert relay 17 in relay 15 position and see what happens.