Or ABS warning light and rear diff light on

[shakey]

rear diff light pops on once i've driven a few hundred metres, the rear diff knob is not pulled to engage and i haven't done so for a while. The rear diff is not locked out, i have checked the vacuum hosing to the actuater and have good vacuum to this point(hissing from one pipe). I am puzzled, any ideas?

[lloydy]

have you tried unplugging the switch by the actuator to see if it still does it? if it stops maybe the switch has a short in it?

[Aidan]

pipes on wrong way ?
blue pipe goes to black side of vac unit
also be aware the switch in the dash has a tendency to get pushed in to the dash so whilst knob appears to be in the switch isn't actually fully switched, a lot of vans have a micro jubilee fitted to stop this happening

[shakey]

Thanks for the suggestions, i will check these out tonight. Should the hose with the hissing(which has vacuum) go to the blue pipe on the actuator?
I really appreciate the help its a new syncro for me, taken me a year to find this one and i'm going through all the usual job lists but this is my priority at the moment.

[Aidan]

if switch is in off position then vacuum should be to the black spigot to pull the unit off (out), should be white pipe to blue spigot, unless someone has had the dash apart and swapped the lines at that end

[shakey]

Thanks Aiden, I have checked hose runs to actuator and its blue pipe to black on actuator. I pulled the pipe and re seated then sat on road side with engine idling adding some revs to get vacuum pressure back and no lights. Took for little test and 100m up the road and a humming noise from dash area and light on rear diff back on. Front diff and de coupler all good and working. Took for a gentle test up a local grit track and tried pulling switch on/off as usual and light still on.

[shakey]

So i have just taken the switch terminals from rear diff and it made no difference. My sysncro has ABS and the warning buzzer sounds and ABS warning light shows as if the diff is engaged but it is definately not, if i pull the relay on ABS (under passenger seat )the relay resets and both diff lock and ABS light go. Then another trip and lights pop back on after warning buzzer. I am now thinking Relay? or how does ABS sense diff engaged if switch cables are pulled? Help

[xriss]

is the orange abs warning light staying off? you might have to get it moving for a little too test this, pm me your email ill send some drawings,you might want too check for brakes in the cable running too the sensors

[shakey]

Thanks for the Tip.There are no warning lights on start or warm up, the bus drives ok and then the ABS buzzer sounds as if rear diff is locked after 400m or so, then another buzzer sounds and then rear diff light pops on followed by ABS warning light. The rear diff is not locked though and the switch is not pulled to engage.

[xriss]

try jacking up each wheel get a multimeter and unplug each wire from the abs pump and test the run from that point down too the sensor spin the whell too get a pulse ....check for consistancy ...move and minipilate the sensor wire while spinning the wheel repeat for the other three wheels...good chance thats the problem...dont worrie too much about the difflight activating as a break in the wire and or faulty sensor will throw up strange anomalies such as the diff lock light comming on....tps do a front sensor with said cable attatched for £77.64...pt# 251 927 808...dont know anything as regards to the rear

[shakey]

Chris, thanks for the wiring schematic, much appreciated. The front sensor you managed source; from which supplier is it from? And does anyone know of a rear ABS sensor supplier, i know VW have stopped stocking this.

[Cruz]

VW Classic parts in germany list the sensors as available

Numbers according to ETKA

front Right 251 927 808 - 89 euros

front Left 251 927 807 B - 137.50 euros

Rear x 2 - 251 927 807 144.38 euros each

Email brickwerks with the part numbers and they will order them in for you and send them out to you

[xriss]

trade parts specialists they had the fronts in a few months back .... http://www.thetradepartsspecialists.co.uk/" onclick="window.open(this.href);return false;

[shakey]

Thank you so much, thought finding the sensors was going to be a real problem.