Polo central locking stops and starts? - Ellie100

I'm a first time poster so please shout if I breach any etiquette or leave anything out.....

I have a 1998 VW 1.4CL Polo. For the past month or so the central locking has been playing up. It works while the engine is running, or shortly after the engine has been switched off, but doesn't work when I try it from cold. If I open the driver's door only with engine cold (CL doesn't work), then start the engine, after a few seconds the other doors will all open.

No other noticeable problems with the electrics. Have charged the battery but that didn't make any difference.

Does anyone have any ideas?

Polo central locking stops and starts? - Steptoe
Hmm, just a wild guess:- when engine running voltage will be slighty higher than when stopped, an extra 1.5 to 2 volts or so, maybe there is a poor electical connection somewhere inside the driver's door which is being overcome by the extra volts. You could check this theory by connecting a battery charger before starting engine, tricky one to find though, start by checking all connectors.

Polo central locking stops and starts? - Ellie100
Hi Steptoe

Thanks for the reply, sorry have only just picked it up as we've been on holiday since I posted. I'll give this a try as it sounds like it's something very like this. Will let you know if I find it!
Polo central locking stops and starts? - kennybase
OK - another wild stab in the dark - but I seem to remember the Polo CL central looking system working on some kind of vacuum system - I may be completely wrong on this, so its just an option for you to check out. Do both the locks work? (ie can you unlock by key both sides) Hope it gives you something worthwhile to look at - and maybe someone else can help!
Polo central locking stops and starts? - Ellie100
Hi Kenny

Thanks for the reply, again sorry for not replying but have just got back from holiday and seen your message. AFAIK it does work on a vacuum but the erratic behaviour seems to be the same whichever side I attempt to unlock........ It does seem to be something electrical but can't find what!
Polo central locking stops and starts? - adverse camber
might be vacuum. Where does it get the vacuum from ? Is it from the inlet manifold or similar ? If the vacuum is generated when the engine is running and there is some pressure vessel that isnt holding the vacuum then that would explain it, especially the action a couple of seconds after starting.

Have you got a manual ? Have a look at any pipes coming off the manifolds.
Polo central locking stops and starts? - Civic8
Should be a vacuum pump in the boot,electricaly operated.system usually plays up with a leak on a pipe in one of the doors,IIRC drivers door is most prone to leak near where it goes through the door/to A pillar,Just a thought
Polo central locking stops and starts? - JohnM{P}
It it's vacuum, locate the pump, remove any carpet, expanded polystyrene casing etc and lower the back seat, so that you can hear if it is running. Then, when you open the driver's door and the c/l locking doesn't work, and you start the engine and the system unlocks after a few seconds, try to determine at what point the pump is operating. This will give clue to whether it's a vacuum leak or a voltage drop. If it's a leak, get it fixed promptly - my '94 Passat c/l eventually gave up completely due to pump failure (expensive) after a while of mis-behaving (due to pipe leak - much cheaper to fix!).
Polo central locking stops and starts? - Ellie100
Hi everyone and thanks for your help so far

I think now that it is probably the central locking unit that has given up as we are getting no life at all when we turn the key in the lock. The connectors seem a bit corroded on this but I have tried to clean them up with no joy. Does that seem likely? I'm thinking of getting a second hand unit (for about 50 quid) and trying that but dont want to if its not likely the cause. Also, when I checked the fuse, this is OK. But it is sparking when I put it back in, which makes me think it might be a short somewhere in the circuit rather than a simple failure of the unit?


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