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240 Central locking is frying the fuses

burk992

burk992

Member
Joined
May 22, 2013
Location
STL
'89 245DL LH2.2 AW70

I can't seem to get to the bottom of this one. The number 8 fuse that controls the central locking and my dome light is continuously blowing fuses to the point that I just have not replaced them any more.

If it blows, the central locking will almost lock all of the doors if I push down, and if I pull up on the lock, it will try to fire the rest of them to unlock. The rest of the locks will kind of move as if they got the signal but don't have enough power to move.

If it has a new fuse in it, I'll be able to use the auto locks a couple of times with no problem before it gives up and blows the fuse. Don't really know where to start with diagnosing this one and I'm getting sick of not having a dome light because this has been a problem since last summer. If I could just get an idea of somewhere to start, that would be much appreciated.
 
You always start in the drivers door. Gotta take off the door panel and look at the wiring. There is a three wire connector along the middle of the door behind the door panel. You can disconnect the door switch and the push pull button at that connector. A broken switch that is around the lock cylinder may be stuck trying to fire the locks. Corroded and fraying wires from that switch to the connector inside the door are shorting together. That kind of stuff is the most common. I've even had the clip that holds this little harness cut through and short the wires. The wires can also fatigue where they go through the door but most of the time it is the other above issues.
 
dl242gt said:
You always start in the drivers door. Gotta take off the door panel and look at the wiring. There is a three wire connector along the middle of the door behind the door panel. You can disconnect the door switch and the push pull button at that connector. A broken switch that is around the lock cylinder may be stuck trying to fire the locks. Corroded and fraying wires from that switch to the connector inside the door are shorting together. That kind of stuff is the most common. I've even had the clip that holds this little harness cut through and short the wires. The wires can also fatigue where they go through the door but most of the time it is the other above issues.
Click to expand...

Thanks for the quick response Dave. I'm pulling into the shop early tomorrow to work on a laundry list of stuff, but this is at the top. I'll report back.
 
pay special attention to where the wires jump from door to A-post/body. This is the place where the wiring is subjected to the most mechanical stess (= door opening and closing) and where those wires have to pass through holes in the sheetmetal.
 
You reminded me of another central locking problem I had. The lock actuator in the bottom of the door had a split boot on it and water was getting in there. The thing shorted internally causing continuous locking on the drivers door. As soon as you opened the door to get out you were locked out. Never mind the battery drain. I've seen the system draw 10 amps. lol.
 
Expect to see this on your power lock accuator and on the key lock wires. It just needs some simple repair/replace of the wire.
Dave B
240doorlock2.jpg
 
dl242gt said:
You reminded me of another central locking problem I had. The lock actuator in the bottom of the door had a split boot on it and water was getting in there. The thing shorted internally causing continuous locking on the drivers door. As soon as you opened the door to get out you were locked out. Never mind the battery drain. I've seen the system draw 10 amps. lol.
Click to expand...

I've lived this one as well..:nod:
 
dbarton said:
Expect to see this on your power lock accuator and on the key lock wires. It just needs some simple repair/replace of the wire.
Dave B
240doorlock2.jpg
Click to expand...

^ This is what mine looked like. Splice in some new wire, solder and heat shrink. Try to keep the same colors on the splice.The wires closer to the "black tube are bit harder. Once you get some good wire on there liquid tape works best.
 
Update: Pulled the wagon into the shed this morning and went to give my dad a hand with some loading/unloading work before I started working on the wagon. Busted my face open and chipped my bottom teeth on a fifth wheel camper that popped up out of seemingly nowhere. Took an emergency visit to the dentist instead of taking the door apart! Tomorrow, I guess... :censored:
 
Sorry to hear about the accident. Dentists can do wonders with new materials on chipped teeth, you'll hardly even notice later.

I did the central locking repair, no corrosion, just cracked insulation, easy fix ;-)
 
Hey y'all.

Unneeded update about my mouth: went back to the dentist, he didn't know if it was fractured or not so he drilled off the top of my tooth to see if there was a fracture that would open up enough to see on an xray. If there isn't, he'll fill it. If there is, root canal so help me god. My mouth hurts.

Anyway, today was 67F in STL so I ripped into my wiper motor because it was parking straight up and down. The ground wasn't touching the top cover and I cleaned all the contacts. Voila! No more ridiculous looking wipers.

Tomorrow, it's pretty likely that I'll finally dig in on the door wiring. While I have you all looking:

There's no difference between a DL and a GL door card, right? I have some massive speakers that I'd like to put in my wagon that I stole from one of the family's parts cars, but it turns out that the speakers are so big that the parts car's door cards had to be cut to fit. The parts car's interior matches mine so I figured I'd just switch them out.

I've also got a fried rear wiper motor that needs looked at. Got a lot of time on my hands since I graduated in December and am still jobless. Smh.
 
about the rear wiper motor, check it on a seperate 12V source. It just might be OK.
cars with a tailgate often have issues with the wiring getting damaged (causing shorts) or broken (causing the component to stop being powered) near the hinge where it goes from body to tailgate.
 
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So we've got a winner! I got the door card off and the plug that goes from the bottom of the lock actuator back into the cabin is actually healthy. I looked deeper in the door and found that the key lock ... mechanism (does that have a name?) was the culprit. So I laid it out on the dining room table and started to clean on it a little bit and it just came right apart. I popped it open and there was no way that I felt like I could get wires back in there, so I went out back behind the shed into the parts sedan we have and took the key lock mechanism out of that car. It was not in much better shape as the insulation had dry rotted, but I cleaned it up and heatshrunk it and spliced it into the actuator harness.

I may have made it a little too long, and upon further examination on reinstallation, I did not lay the wires over back in the pattern that they were in on removal, so there might be some strain there. I also did kind of a ratchet job of splicing and dicing. Put it back in, and voila, power locks.

However, I now have power locks that lock when pushed down without blowing the fuses, but when I pull up on the actuator, only the passenger rear door slides up, the rear driver side lock slides up a bit and doesn't finish, and the passenger door does not budge.

I also must have reinstalled something wrong, because when I lock/unlock the door, it now has a lot of resistance to it. I dunno.

Janspeed said:
about the rear wiper motor, check it on a seperate 12V source. It just might be OK.
cars with a tailgate often have issues with the wiring getting damaged (causing shorts) or broken (causing the component to stop being powered) near the hinge where it goes from body to tailgate.
Click to expand...

That's what I was thinking about doing too, but that will be the next step after I finish up this problem first. The thing about the rear wiper is that for the past couple of months it was working intermittently - I would turn it on, sometimes it goes, sometimes it wouldn't. If I left the switch on, maybe I would get a few miles down the road and it would actuate a few times but then it would quit again for a while. Maybe the magnets on the inside came loose? Or a multitude of other things.
 
1) The "new" door cards should fit. The only time the cards are different is if one has roll up window and the power window. But they will still fit.
2) The doors that do not unlock could have the lift motors binding.
 
More fun. Got everthing buttoned up yesterday and went to the cafe my girlfriend works out to have some coffee (where I wrote my last post), and then when we left, got in the car, started it, and immediately my fuse panel started billowing smoke. Opened it up and the fuse was so melted that the copper was bright red.

burk992 said:
I also must have reinstalled something wrong, because when I lock/unlock the door, it now has a lot of resistance to it. I dunno.
Click to expand...

I wonder if I installed the key lock mechanism, I didn't seat it correctly and something stuck open when I unlocked the car door? Bout to eat some breakfast and rip into it again.

At this point I'd like to thank everyone who has posted in this thread because you guys have helped quite a bit. I'm not much of an electrician.
 
Sorry for the double post.

Got the door card pulled off and gave everything a look, nothing is melted or anything. I put a new fuse in and tried both the outside and inside lock and when I pulled up on the inside lock for more than a second, immediately the fuse starts to smoke and goes, so I guess there's some extreme draw there. Is that indicative of the lock actuator being bad as well? Possibly a problem further up the harness towards the cockpit?
 
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