safulop

OK, there have been a number of threads mentioning how the central locking system often develops a mind of its own after so many years. Mine locks and unlocks itself randomly at times. This poses a security issue, as I often return to my car at work to find it unlocked. It is also dangerous to leave keys in the car, as some have found out.

I realize there is some fuse that can be removed as a band-aid for this problem, which will then give the car full manual locks. But what is the eventual solution to the electrical gremlin? I'd like my shop guys to look into it, but I don't know yet where to begin. Could it be arcing in the lock switch button?

Stromius

Check the wire to the plunger (aka door switch) in the doors. Good thread: https://rennlist.com/forums/928-foru...ht=door+switch

safulop

Well that may bear checking, yes. I might have wanted to mention, though, that some clever dick years ago installed a remote system for the locks, so I have a key fob which locks/unlocks all doors as on a modern car. This system itself could be faulty I suppose, although this seems to be a very widespread issue with these cars with or without an aftermarket remote system.

Nicole

On my first 928 - an 88 S4 - I had a similar problem. If I locked it from the passenger side, it would lock and unlock immediately thereafter.

It turned out the lock motor on the drivers side was not locking all the way. Some sensor must have told the system it was not locked, so it completely unlocked itself again.

I played around with this for a while, and was able to adjust the motor such that the system would work flawlessly.

dprantl

I just had a similar problem. When below 32 deg F, the locks would have a very hard time locking and occasionally one side would not lock all the way. The central locking brain detects this and then unlocks both doors right away. I temporarily fixed this by unscrewing the door lock **** cap, then carefully spraying a tiny drop of PB Blaster down the metal shaft, then put the cap back. Problem solved and it has not reappeared in the last 2 months.

Dan
'91 928GT S/C 475hp/460lb.ft

Mrmerlin

if you have removed the lock ****,
then make sure that both the **** surround part,
and the **** screw are not too tight,

either one of these will cause the lock to bind and create the problems you describe

Alan

I think it should be obvious to you that if you have aftermarket stuff attached to your locks you need to remove that first to eliminate it as a cause. Otherwise its likely loose connections that cause random locking & unlocking events.

The more commonly reported issues are cycling after you initiate a lock or unlock - you don't have this - so its not obvious its an adjustment issue.

I suspect the most likely cause is a crappy aftermarket lock module install - these are notorious for botched up poor connections...

Alan

safulop

I give best odds to Alan's explanation this time out. I guess I have to get the aftermarket remote locking thing dismantled or scratched completely out. The locking system locks just fine and stays locked; it also unlocks perfectly well. The problem is it quite often does either one on its own. Sometimes while I am driving the car, sometimes when it is just sitting there.

-Sean

michael j wright

The fuses that you asked about in the op are located just above the CE pannel in inline fuse holders. Should be black with red wires/black stripe.

blown 87

Shhh...............those aftermarket installs are making installers money when they put them in, and they are making mechanics a lot more money to figure out what is wrong and take the POS units out.

I cringe every time i see a scotch lock and to some extent butt connectors.
It means that who ever has been working on it, only cared about speed, not the quality of the work.

I think the blue Scotch locks about paid for the blower in my corvette.

safulop

Have to get my mechanics to find the POS unit first. I'm hoping that it will be fairly obvious to people who know what they are doing on these cars.

dprantl

On an '88 it's probably behind the glove box or around the fuse panel.

Dan
'91 928GT S/C 475hp/460lb.ft

Landseer

Theres a 9 page technical service bulletin just focused on the troubleshooting of the door locks that might help.

safulop

Bumping up,

can somebody tell me how I could access the TSB Landseer mentions? I'm still having some random lock problems, and no problems can be located in the fuse panel.

-Sean

Landseer

I found it in PDF form in the technical bulletin section of the Morehouse CD's.
Came out in 83.
References to lock motors and their switching methods, and linkage mechanical setup and wiring connectors carry forward in principle.

Specific terminal references to CE panel, though, are for earlier cars.

Triangulation with 88 S4 wiring diagram 97-287 (body or page 3) is needed, but straightforward because that diagram is good. Need page 2 also, because it includes the door contacts that end up giving a signal to the window regulator relay, which is important to the function.

However, if it were my car, first thing I'd do would be diassemble and polish clean ( else buy new/replace ) the door pins and hatch pin. I've solved locking problems on 84, 85 and 86 that way and have avoided the need to get deep into the 9-pager document for the mechanical setup. You can't loose much --- the cleaning of those pins is an essential part of a good ground point cleaning regimen. Should be the cheapest and easiest first step, anyway, in a shop's approach to the locks.

That door pin 'factor' should be same for your car, even with your remote locking device.... I think.