W124 - Symptoms of a failing Central Locking pump

[Vectrolosys]

Hello,

With the engine off, the pump will only work sometimes to either fully lock or unlock the car, only the door you unlock will unlock.

However, when running and the engine is producing a vacuum, the doors will either unlock or lock depending on the previous position of the drivers side door locking pin.

I am going to try tapping the pump to see if I can bring it back to life, but I was wondering if this was a typical symptom of failure.

Thanks,

James

 

[neilrr]

Leak?

 

[Frank O' Phile]

Leak?

Agree.

If it opens with the engine running, then your pump works.

Finding a leak may be difficult but it is the likely cause.

Does it happen the same using the passenger door, or the boot?

 

[Vectrolosys]

Thanks all,

I'll try the other doors, I thought I'd tried the passenger door, but maybe not.

A leak sounds plausible as I was poking around quite a bit during the Waxoyl!!

 

[Spoonman]

The central locking on my W202 doesnt work but I cant remember actually trying it with the engine on. I'll fiddle round with that see if it does work with the engine on.

 

[Rob77]

The central locking on my W202 doesnt work but I cant remember actually trying it with the engine on. I'll fiddle round with that see if it does work with the engine on.

Worth checking the fuse too. That stopped mine working a while back.

 

[grober]

Sounds as if you have a leak somewhere or your pump is failing. The central locking system is ONLY supplied from the electric pump under the rear seat. It has no connection to the engine vacuum system which only acts on things like the headlight leveling and heater flaps. The only difference when the engine is running is that the car voltage supply may be slightly higher.

 

[Vectrolosys]

Thanks for clarifying how the system operates, I was under the impression that the pump just supplied vacuum for the system when the engine was off, I thought the system was similar to what I remember my old W123 being like.

The fuse theory makes sense. I had to clean the fuse for the comfort module recently, as the sunroof just suddenly stuck in the open position!!.

Thanks,

James

 

[Vectrolosys]

Well, a brilliantly easy fix, that I wish I'd checked earlier, given my experiences with these type of fuses and their corrosion issues. Anyway, replaced the fuse, Central Locking now works once more.

Makes up for having to remove the carpets to dry out someones previous Valeting attempts, the foam on the carpet undersides were somewhat sodden with water!!.