Seized lock on external locker - any suggestions?

[allegoricus]

The lock on one of the external lockers on our 2011 Bailey Unicorn Valencia is seized and i'm unable to fully insert the key.
Fortunately the locker is the one that matters least - it gives access to that additional water tank (that we haven't bothered to use) so it hasn't been an urgent concern.

However, we're now thinking of selling the caravan, so fixing it has risen to the top of to-do list!

Over time I've tried squirting lubricant (silicon/WD40/locklube at different times) into the lock but without success and the lock (or at least the last pins within) remains stuck.

Short of resorting to destructive methods, does anyone have a suggestion for how to overcome the problem?

[Griff]

Had a similar problem but not caravan related, Plus Gas solved it for me as it creeps into cracks well.

[Guest]

WD40 is NOT a penetrating fluid.    A magazine tested penetrating fluids and the winner was a mix of ATF and acetone.  

 

Plus Gas is very good.  But I would insert a screwdriver and try to turn the whole lock round.  You can look at the others to see which way to turn it.

[allegoricus]

Yeah, I know WD40 doesn't possess magical properties but, when the other fluids didn't work, I gave it a go. :-)
I'll try Plus Gas and report back.

I'm reluctant to be brutal if there's any other way.

Thanks to you & Griff.

[allegoricus]

No luck with PlusGas, 

I've also found my lock picks and gave those their first outing in anger but without success. They weren't able to move the last tumbler. :-(
I've even attempted to find a support contact address on the Thetford web site but it looks like they don't want to hear from end users.

 

 

Edited October 22, 2020 by allegoricus
added para

[Paul1957]

Has the key ever unlocked the door, just thinking if not then maybe you are using the wrong key. If you have access to the back of the locker door then you could probably remove the lock. Failing that a large screwdriver inserted in the key hole and turned might be able to break it and then another lock can be put in - if this might damage the door then use a drill in the key hole and drill the lock out.

[allegoricus]

22 hours ago, Paul1957 said:

Has the key ever unlocked the door, just thinking if not then maybe you are using the wrong key. If you have access to the back of the locker door then you could probably remove the lock. Failing that a large screwdriver inserted in the key hole and turned might be able to break it and then another lock can be put in - if this might damage the door then use a drill in the key hole and drill the lock out.

There's a single key for all the locks on the caravan and, yes, it has unlocked the door in the past. The door provides access to an auxiliary water tank which we don't use. For that reason,  we haven't opened the door in quite a long time.
I think, of the alternatives you suggest, I'll drill the lock if it doesn't yield to my next attempt, which will be probing with a nail file - SWMBO won't permit me to use a steak knife.