Diff Lock Woes

[Martin62]

I hope somebody can help me with this issue.
The diff lock on my 7a Coupe refuses to disengage !
It seems to engage OK and I can hear the relay in the controller under the rear seat click when I try to disengage but nothing happens.
Yesterday I had to crawl underneath to disengage it manually.
Although I can tell it's engaged due to the tyres scrubbing, the green light in the switch doesn't illuminate.
I have swapped the switches as I have a spare but no change.
I notice I am able to move the rod from the actuator under the car in and out without any significant resistance, is this normal ?

Any advice greatly appreciated.

Martin

[UrS4boy]

Diff Lock 101:

Could be as simple as a leaking vacuum hose.

Lots of info at Diff Lock 101:

http://forums.quattroworld.com/s4s6/msgs/170940.phtml

[Martin62]

Thanks, that's just the info I need.

Looks like blue hose is probably the disengage vacuum supply, I will try it out.

[UrS4boy]

Thanks, that's just the info I need. Looks like blue hose is probably the disengage vacuum supply, I will try it out.

Yep, either the blue-striped or the yellow-stripped one. (I've never bothered to figure it out since mine works fine). Let us know (please) and I will add the info to Diff Lock 101.

[ericd]

last time I had this, it was the one way valve (half black/white) under the seat

[UrS4boy]

last time I had this, it was the one way valve (half black/white) under the seat

Like this one (also flagged in Diff Lock 101) (below). Typically when that one fails, the diff will engage, without any intervention by the driver, everytime the boost comes on.

[Martin62]

As part of my sub-frame refurb I have the actuation mechanism out and I can confirm that on my car:

Pipe with yellow stripe = engage vacuum

Pipe with blue stripe = disengage vacuum

Cheers,

Martin