Central lock help before I scrap the system

[cabmandone]

I have a problem where my central lock doesn't work. When the doors are closed I can manually lock both doors which is normal from what I gather. The problem comes when I try to use the key to lock the doors. When I press the central lock button inside the car, I can hear the relay in the trunk click but nothing happens. When I try to lock it with the key, I get no sound at all. I can't find a good flow chart for troubleshooting the locking system and I'm about to remove it all and install manual mechanisms with the lock and unlock tab that the tumbler contacts. I'd like to try to keep the car original but this system is making me pull out what hair I still have. If anyone has a good step by step for troubleshooting, please pass it on. I'm good with electrical and can follow schematics but I can't find anything to start with.

I'll be posting a wanted ad for a new door mechanism later but again, I'd like to stay original if possible.

[mtb001]

The Bentley manual has very good detail of wiring, used it to identify bad module. There are threads on the mechanical arm that breaks, causing 1 door not to lock, it could be both doors have similar issue.
Since the module was bad, i rewired mine with 2 relays to allow key lock/unlock, then attached key-less entry to complete. Since I am removing center console, removed the push button as well but sure i could wire it back in if needed.

I can scan in my modified drawing tomorrow if needed but check the door hardware first. Modules are anywhere from $80-$300.

[86 911 Targa]

Here:



pm me as needed.

Good luck,

Gerry

[cabmandone]

mtb001,
One of the first things I checked was the mechanical arm that actuates the lock on both sides. Both are fine. I do have to correct my o.p. I put the key in my passenger side door and could hear the module in the trunk clicking when I turned the key but noting happened in either door. In the drivers side, I get no noise at all. I am curious if the previous owner removing the alarm system could cause a problem with the central lock system.

On the drivers door, I'm guessing it could be a micro switch problem but that's just guessing. I need to find out how to bench test the components.

I'm thinking after reading about the number of problems with this system that keeping it original doesn't really mean that much to me.

[porschenut]

I've got quite a bit of experience with this system and can offer some thoughts. First, the fact that you can hear a click in the module when you turn the key in the passenger side lock tells me that the passenger side microswitch is working. Since you can't hear it when actuating the driver's side, I'd guess that side's microswitch has failed.

If neither door will lock or unlock in any way except manually, then I would also suspect the actuators inside the doors. Those are common failure points.

It is also possible that the ECU itself is no longer operating 100%. I don't know of any test procedure to diagnose that.

I would urge you to not give up on the CLS. Originality is very important these days if you're at all concerned about your car's value. The electrical components in the system are 2 microswitches (each door), 2 electric actuators (each door), the button on the center console (seems to be working), and the ECU in the trunk. Neither the microswitches nor the actuators are terribly expensive to replace, both are readily available new or used, and are by far the most common failure points. The actuators can be removed and bench tested easily outside the car by applying 12V to see if they respond. That's where I'd start.

[cabmandone]

I found the drivers side micro switch is bad. I tested the actuators and both work. I've decided to just remove the system and put in manual locks. In the long run it's less trouble. It's a 2 door car, I'm 6'1 and my kids say I have "monkey arms" so I guess I'll just put them to use.

Thanks for the help.

[jcgranato]

Not to hijack but my central locking system on my 85 Targa is having trouble also. I cannot lock or unlock either door with the key. Also, when I push the central lock button, both doors lock then immediately unlock. To note, I can manually lock both doors from the inside using the rotating lock knob on the door panel. Any insight would be great.

[cabmandone]

You should be able to lock either door with the button or knob when the doors are closed. If you open the door you won't be able to push the lock down. I believe the system works off of ground. If it loses ground it will not lock. Does your car have any other "flukey" behavior? Or is it just the central lock system?

[jcgranato]

Just seems to be the locking system. Yes with both doors closed, central button pressed, doors lock then immediately unlock. Strange.

Only other gremlin is the power seats do not work. Haven dove into that yet.

[cabmandone]

Originally Posted by jcgranato

Just seems to be the locking system. Yes with both doors closed, central button pressed, doors lock then immediately unlock. Strange.

Only other gremlin is the power seats do not work. Haven dove into that yet.

I have intermittent seat problems. There are contacts that need cleaned if I recall correctly. I'd check your door latches to see if they latch tightly. There is no sensor to the latch but after removing the central lock latch from my car, the only way it can know the door is open is through the latch to ground. Either that or there is a door switch mounted somewhere I can't see it.

[techman1]

Just seems to be the locking system. Yes with both doors closed, central button pressed, doors lock then immediately unlock. Strange.

Is it possible one of the door lock microswitches is stuck in the closed position? If you use your key to lock the door from outside, what happens?

[cabmandone]

When you try to lock from the outside, can you hear anything clicking? Thats how i figured out my micro switch on the passenger side was working and not the drivers side. Well that and a meter checking continuity when the switch was turned. On my car the two female pins were power and the male pin was ground on the microswitch. I checked each to ground on both sides of the car. On the working side there was continuity when the key was turned on the working side but not on the nonworking side. I hope that all makes sense. I also applied 12 volts to pin 1&5 of the actuator (male pins) and switched polarity to check up down function of the actuator. I hope this helps and doesn't confuse you more.

[porschenut]

Since both doors lock and unlock when you press the console button, the actuators are both working fine. I would guess the button module itself is faulty (sending a repeat signal each time it's pressed), or the ECU may need repair. A bad microswitch (or two) might be the culprit too, especially since neither door locks or unlocks from the outside.

[wally509]

Or one of the microswitches inside one of the door lock actuators may have failed. If the control unit doesn't get the signal from both actuators they have moved, it will fail safe to the unlocked position.

I stumbled over this when fixing my system recently. I had a failed actuator in the driver's door. If I pressed the central lock button the pass side would lock then immediately pop back up. However, if I moved the rod by hand on the driver's side while I pressed the button, they would both stay locked.