SL350 central locking problems

[woodysl]

Car has been garaged all winter with C Tek battery conditioner and dehumidifers, doors not locked but boot closed to stop battery drain. On trying to open boot, would not open and central locking not working. As emergency key would not open boot (as normal!!) had to resort to removing boot stop light and then opening manually. Checking battery showed 12.6 volts, so not that. Checked all the fuses behind drivers seat, all OK. Removed PSE pump and rebuilt with new impeller, its showing 4bar pressure on outlet, so pump working OK. Infrared locking for doors works ok. Boot however, will not latch closed and normal central locking will not operate, so supsect an electrical/ CAN BUS fault. Any ideas what to try next??

 

[Petrol Pete]

One question .

Does the car start ?

 

[woodysl]

Car starts and drives no problem, no warning lights showing. Have tried all electrical items associated with the fuse board behind the drivers seat, and everything works OK. Fuse 71 checked and is OK. Everything works except for the main central locking system. Rebuilt the PSE pump and there was no signs on water ingress or dampness in the plastic pump housing box. Any ideas??

 

[Petrol Pete]

I assume you have good quality new batteries in the key fobs ?

 

[Monkeylegend]

The charger was connected to the consumer battery presumably?

 

[woodysl]

The charger was connected to the consumer battery presumably?

Yes, connected to battery in boot. Battery only 2 years old and has always had a C TEK charger coupled up when the car stands for any length of time. Battery shows 12.6 volts so thats not the problem

 

[woodysl]

I assume you have good quality new batteries in the key fobs ?

Yes, new batteries in both key fobs, neither of them will initiate central locking, but infrared locking works with both of them. It seems to be a problem with powering up the PSE pump as the soft close mechanism will not work on the boot and it will not latch even if you push it shut, so it looks like an electrical problem. Boot latch closing mechanism was changed for a new one couple of years ago so I know its not that. I have a feeling it may be the dreaded can bus corrosion problem, I understand that they are susceptible to corrosion of the can bus system running under the carpets, if dampness gets in.

 

[woodysl]

Stranger and stranger!!! Had stripped out the boot liner to check connections to boot latch mechanism and to fit a new boot rear light. After fitting new light, went to check if working OK to be met with a full return of all cental locking functions. Clever these Mercs, they can fix themselves!! However, in future I will make sure that the car is used at least once a week to keep all the systems working properly