My 1996 1.4CL 6N1 Polo has developed a strange fault. The other day the central locking stopped working completely. I could only open the front doors and the boot with the key. I extracted (with difficulty) the polystyrene foam moulding that is the pump holder/first aid kit holder from the boot after first removing the central locking pump from the moulding, I then manually opened the petrol flap by pulling on the actuator rod and filled up with fuel at home. I removed the electrical connector to the pump to check for corrosion on it and the pump conector pins (none found) and put the pump back in place wrapped only in bubblewrap (without putting the foam moulding back in) so the car could be used temporarily. Now the weird thing. For no apparent reason the central locking started working OK. Great I thought - problem solved - must have been a slightly dirty connection on the multiblock that I hadn't noticed. However, the following day my wife was outside and heard the central locking operate on its own. We then both witnessed the car randomly locking and unlocking itself repeatedly with a gap of varying length between each action. I've temporarily removed the pump to stop it cycling and flattening the battery plus, if we go out in the car we don't want it randomly unlocking itself whilst it's parked up and we are away from it. So, anybody come across this random locking and unlocking behaviour before and knows what the culprit might be?

It could be that you need a new pump mate, i haven't had any experience with this type of thing but if there is someone close by that you could try there pump see if that makes any difference, if not, then go to your local scrapyard and by one, they shouldnt be much, i think i have one in my shed somewhere if you need one and thats the problem, hope this helps mate

Our 6n2 was locking/unlocking itself and it turned out to be a vacuum pipe that had become detached.

It could be that you need a new pump mate, i haven't had any experience with this type of thing but if there is someone close by that you could try there pump see if that makes any difference, if not, then go to your local scrapyard and by one, they shouldnt be much, i think i have one in my shed somewhere if you need one and thats the problem, hope this helps mate

Thanks for that offer - I'll do more research to see if the pump (or it's control circuit board) is playing up or showing signs of water ingress. These cars don't have a CCCU I believe so I think I'm correct in saying all the 'intelligence' is in the pump electronics. I know some people have reported problems if the pump gets wet but there was no sign of moisture on the pump when I removed it. Two additional questions that hopefully someone will know the answer to:

1. Last night in preparation for the scenario of needing a new pump, I searched on eBay. I found several with the same part number but noticed the last letter of the part number differed. What does the last letter signify - is it to designate the manufacturer or country or origin? i.e. mine is 1H0 962 257 D but for example one on eBay has the same part number but ends in an A - does it matter?

2. When removing the Polystyrene foam insert the pump sits it to get at the petrol flap actuating rod, I slightly damaged the foam. I'm going to glue it before I put it back but wondered if anyone has sussed a way of getting the polystyrene foam insert back safely without damaging it? There's clearly a knack/technique to refitting it - I just wondered if anyone has sussed out what it is?

Our 6n2 was locking/unlocking itself and it turned out to be a vacuum pipe that had become detached.

Interesting - was it disconnected inside a door or the tailgate at a locking actuator or at the pump end? Could you hear the pressure or vacuum effect of the air movement from the open disconnected pipe quite clearly when it operated?

Well if it is the pump mate, depending where you live i can meet you and give it you? Or you can just pay postage for it, ill check to see if i still have it but if you want it let me know mate

Well if it is the pump mate, depending where you live i can meet you and give it you? Or you can just pay postage for it, ill check to see if i still have it but if you want it let me know mate

Thanks for your very kind offer. I'm in Nottingham - quite a distance from you so meeting up is probably not feasible/practical. If it does turn out to be the pump (as opposed to say a faulty door switch or a break in the wiring) I would be really grateful for your pump and would of course pay the postage plus whatever you wanted for the pump. I will keep you posted when I have more info and have done more diagnostic work. I'm going to jiggle wires in the rubber trunking that goes between the body and the doors to see if that makes the fault occur again and also listen for air leaks when the system activates in case that is the cause.

Common areas for a vacuum leaks are the connectors on the door frame & the fuel flap actuator

Common areas for a vacuum leaks are the connectors on the door frame & the fuel flap actuator

Thanks for this - I'll check there first - incidentally, is it normal to be able to hear the 'hiss' or 'suck' of a leak when the central locking system cycles?

Well if it is the pump mate, depending where you live i can meet you and give it you? Or you can just pay postage for it, ill check to see if i still have it but if you want it let me know mate

Thanks for your very kind offer. I'm in Nottingham - quite a distance from you so meeting up is probably not feasible/practical. If it does turn out to be the pump (as opposed to say a faulty door switch or a break in the wiring) I would be really grateful for your pump and would of course pay the postage plus whatever you wanted for the pump. I will keep you posted when I have more info and have done more diagnostic work. I'm going to jiggle wires in the rubber trunking that goes between the body and the doors to see if that makes the fault occur again and also listen for air leaks when the system activates in case that is the cause.

Yeah thats fine mate just keep me posted on whats happening mate and ill dig pump out if i have it mate waiting if you need it pal :)