Problem with the 2009 1.4tdi BNV this time:

 

Brake pad wear indicator coming on intermittently. Checked wheel end and no sensor fitted and cable has been cut and joined previously. I opened these up and cleaned them, and soldered together and heat shrinked.  Whilst doing this, separating the wires caused light to come on, and soldering together cancelled it, so I thought I'd solved it. However, on some journeys (first journey, coldish), the light is still coming on, so i suspect a wiring fault further up the circuit.

 

Does anyone know where the wire routes? I see it going behind wheelarch liner and can hear it behind dash it sounds when rattled. Does it end up in the ABS plug with the adjacent ABS wiring, or does it go elsewhere?

 

Goes straight to pin 1 of the 8-way connector on the back of the instrument cluster.  Might well be the solder joint of the male connector to the board rather than the wire itself.

 

A simple fix might be to find someone with VCDS to re-code the instrument cluster to ignore that wire.  Two minute job.  

 

Otherwise I would extract the cluster and remove the circuit board from the plastic housing, then reflow that joint.  Can probably get enough access without removing the needles and bezel.

Thanks Wino,

 

I should have remembered that as we discussed it recently when i had a fault with that instrument cluster and I initially thought pin 1 could be the culprit :

https://www.briskoda.net/forums/topic/490180-blank-cluster-dash-display-and-immobiliser-killing-engine-wiring-help-needed/

 

So I have already reflowed all 8 pins there. I don't fancy trying to trace the wiring behind dash, so that just leaves trying to check it further up from the joined sensor wires in the wheel arch, or trying to get it disabled by someone. 

 

thanks for your help again, saved me heading off towards the ABS unit...

Wino, another quick question if i may:

 

Does that red wire to pin 1 in the cluster return an earth from the pad sensor from the yellow wire? ie. when the pad sensor is closed (or the two wires shorted together) it provides an earth to pin 1, and when sensor open no earth provided and dash symbol illuminates?

 

If so, I could maybe provide an earth to red wire at the dash 8 pin connector (from pin 8 wire) to bypass any damaged sender cable - first to help diagnosis and maybe as a permanent fix/bodge.

 

cheers.

Yep, just as you say.

 

Edited 21 March, 20215 yr by Wino

thanks for quick reply - i'll investigate that tomorrow.

 

for some reason i can find more motivation to work from the drivers seat into the dash cluster than with my head in the wheel arch dealing with dirty and rusted fasteners everywhere  

Has the other cluster problem stayed away?

 

Yes, the total dash loss followed by immobiliser cutting in immediately after starting has not reoccurred after I reflowed all pins of both connectors on the cluster.

 

However I didn't identify any actual fault at the time though (assumed a hidden dry solder connection of one of the power feeds) so always feel a bit unsure that it was something I've done has fixed it or that it was a very random fault.

 

This occasional pad warn light was going for a few weeks before the main cluster fault, and has continued afterwards, but it is always intermittent. 

 

My thinking now is if I jump the wires at the connector block and fault goes it will suggest loom to sensor fault, but if it remains it will suggest cluster PCB.

 

I like your thinking, and am glad to hear the other fault seems to have been cured.

was cold this morning (frost) and the brake pad warning light stayed illuminated on starting (even though both wires soldered together at wheel end). Usually  subsequent trips throughout the day do not have the light illuminated.

 

so I went ahead with the earth bridge discussed above (joining pins 1 and 8) on the 8 pin connector behind cluster, took about 5 mins. Used some heavy duty solid copper house wire as it fitted firmly alongside the pin bodies in the back of the connector. Light now stays off, but it always did after first start, so real test will be tomorrow morning. 

 

if it works, we'll see how long it takes me to remove this temporary fix and do properly , and if it doesn't work then I'll have to look at the PCB connections again...

well that is three days of cold starts and daily running, and no warning light at all - so looks like the bridge wire solved it. Must have been a break in the loom between dash and wheelarch, and the bridge has bypassed it.

 

I did notice that one of the brake light bulbs was blown, so I replaced that yesterday. Cant be sure how long it was blown for, but think that must be coincidence as I believe the brake pad wear circuit just monitors that and not other brake items? Could remove the bridge to double check now that the bulb is working, but will leave well alone until after tomorrows MOT....