View Full Version : DIY: Centrail Locking Pump Rebuild

11-20-2014, 08:29 PM
Has your Central Locking Pump gotten noisy lately or failed? If you've looked for a replacement, you may have noticed that a new pump is obnoxiously priced and a used pump seems to be running ~$100 on ebay. I rebuilt my pump for the low cost of $25. Here's how:

If you need instructions on how to get the pump out of the car, look here (http://www.audiworld.com/tech/elec131.shtml).
My car uses the facelift "N" type pump, but this procedure should work the same for the prefacelift "B" pumps. The common failure with these is that the graphite rotor eventually explodes and the pump no longer works.
http://i254.photobucket.com/albums/hh91/bshusted/Mobile%20Uploads/IMG_20141115_183443_674_zpsgynorghm.jpg (http://s254.photobucket.com/user/bshusted/media/Mobile%20Uploads/IMG_20141115_183443_674_zpsgynorghm.jpg.html)

To open the box containing the pump, gently pry up ward on the tabs that hold the white lid down. Work your way around the lid. It will simply lift off. The circuit board underneath will lift out. If it seems stuck, you can push on the brown and black plugs from the other side. To inspect the pump rotor, remove the three brass colored screws and gently lift the top.
http://i254.photobucket.com/albums/hh91/bshusted/Mobile%20Uploads/IMG_20141115_194542_125_zpsaboza5vk.jpg (http://s254.photobucket.com/user/bshusted/media/Mobile%20Uploads/IMG_20141115_194542_125_zpsaboza5vk.jpg.html)

Of course Audi won't sell you just the rotor part, otherwise they wouldn't make hundreds selling you an entirely new unit. Fortunately, VAG has been using these this type of vacuum actuated locking pump for a while in many models. I bought a used pump from a '90 Corrado on ebay for $25. The part number is 535 862 257. I'm sure that units of a similar vintage would work just as well. The advantages of going this route are:

the graphite rotor is twice as thick (hopefully preventing future failures)
no locks or keys need to be reprogrammed

When your replacement pump parts arrive, open the lid as you would on the B5 unit. You'll notice that internally, the Corrado or other model part is very similar.
http://i254.photobucket.com/albums/hh91/bshusted/Mobile%20Uploads/IMG_20141115_183501_588_zpsb4gatlo8.jpg (http://s254.photobucket.com/user/bshusted/media/Mobile%20Uploads/IMG_20141115_183501_588_zpsb4gatlo8.jpg.html)

Originally I thought I could simply swap over the graphite slices into the B5 unit, but the intake and exhaust ports are in different locations. As a result I swapped in the motor and graphite bits together. The motor wires were simply soldered onto the existing wires. The rubber mounting parts simply push through the holes in the case.
http://i254.photobucket.com/albums/hh91/bshusted/Mobile%20Uploads/IMG_20141115_183625_928_zps9wezitne.jpg (http://s254.photobucket.com/user/bshusted/media/Mobile%20Uploads/IMG_20141115_183625_928_zps9wezitne.jpg.html)

In my case, the Corrado pump had the pressure switch on a separate port, so I sealed one with epoxy. The other port was simply connected and the unit reassembled.
http://i254.photobucket.com/albums/hh91/bshusted/Mobile%20Uploads/IMG_20141115_194613_542_zpst43wr8oi.jpg (http://s254.photobucket.com/user/bshusted/media/Mobile%20Uploads/IMG_20141115_194613_542_zpst43wr8oi.jpg.html)

Test and reassemble and your car should be good as new for much less than another failure prone B5 pump. Hopefully this will help some people save some cash. Let me know if you have any questions.

11-22-2014, 05:54 PM
awesome, sticky material here.

11-23-2014, 04:02 PM
The weak point on these pumps are the graphite piece. [headbang]

11-23-2014, 06:16 PM
The weak point on these pumps are the graphite piece. [headbang]

the older mk3-era pumps have larger graphite pieces and are much less prone to failure.

11-23-2014, 06:30 PM
the older mk3-era pumps have larger graphite pieces and are much less prone to failure.

Exactly. Which I imagine is why the price of the Corrado pump was very low with many options. The failure rate is low, so the demand and price follow. I'm confident in the new (old) parts outlasting the rest of the car now.