E39 Door lock problem.

First thing I would try is to squirt plenty on lube in the lock, then use the key to work the lube around the lock barrel/tumblers.

If all of the keys work in the ignition but none of them work in the doors then either the door or ignition lock sets have been changed and are no longer the same, or the key is not going fully into the door lock.

You could be right, but as the door lock barrel is subject to so little wear, I'm inclined to think it's more likely that the tumblers, pawls, in the barrel, whatever they are called have siezed. Not the barrel itself. That seems quite free. Or, or something has broken, stopping the barrel from turning. The key enters fully. It just doesn't turn. Mike.

If you think you have seized tumblers, then you need graphite.

First I need to find out what's wrong with it. Graphite is not going to free it off. Whatever is preventing it turning is mechanical. Of that I'm certain. I'm not concerned about fixing it. Whatever the cause I'm quite capable of either repairing it or fitting a new lock. I just thaught if it was a known fault it might save me some time. Mike.

There is no known fault that I am aware of.

Eh! There is - otherwise it would work ------- Oh I see you are not aware of the fault just that there is one or you know there isn't a fault and you can't understand why it wont work.

It is possible to dismantle the lock but unless you class your mechanical skill akin to that of a watchmaker then I'd try the penetrating oil route first possibly playing a hair drier on it at the same time to get the thing expanded slightly and maybe free of anything that might be gumming up the works.

Often well meaning persons put a little oil in the locks on a service but often the oil can is not "gun" oil or light machine oil but heavy engine oil - it has been known that people use cooking oil to lubricate delicate things like locks and sewing machines and wonder in 2 months time when the thing sticks together like glue it don't work.

Just a thought!

'Course, Jeffy is also not "aware of" things like evolution.