Educate me on electrical fault finding and fixing please?

[Beanwood]

My Discovery 3 has been sat idle for about 3 months over winter as it needs an MOT. (I was waiting for dry day to fix the SRS fault, and also to fix the rear door that no longer opens from the outside.)
First bit was easy - the door - a cast metal part had snapped, but it's a £25 ebay replacement to sort it - so that's on the way.
SRS on the drivers seat was the other issue - but fiddling with connections under the drivers seat appears to have solved that for now at least.
But as it's bee sat unuded, now I have different issues - various warning lights and electrical faults presenting themselves, with the worst being it tries to brake one front wheel for no apparent reason. Irritaatingly I can't see a fault code for it - but there are plent for 'Lost connection with....' messages.
I imagine a lot of this is going to be tracking back to poor connections, but I need some guidance please - how do I clean electrical connections? They'll all likely be issues in plug/socket connections or maybe brake sensors? What is the best way to clean these things up? I have a WD40 electrical contact cleaner spray - but do I need a little wire brush or similar ? (Any reccomendations?)

It's a D3 so I count myself lucky I've been fault free for two years.... but I'd really like to sort this out now.

Thanks

 

[Robotstar5]

I usually plug/unplug a few times to clean the contacts then washout with contact cleaner unless you can see a heavy build up of crud then my favourite weapon is a glass fibre pencil to clean them off.

 

[willie.macleod]

It might be the dynamic stability control kicking in if its braking just one front wheel. If the vehicle has been sitting then incorrect tyre pressures, steering angle sensor out of calibration or even just worn bushes could do that with minimal fault codes logged.

Make sure you have a decent battery fully charged, clear the fault codes, drive for a bit and see what comes back. Post the codes for any faults that do reappear back here, there are too many connectors to go round unplugging at random.

 

[reb78]

Exactly what Willie says. Is start with a decent battery and imagine a number of things will then dissappear.

The braking sounds like the SAS could be the culprit. Do a search as there's loads out there. Mine came unstuck from the steering column so it thought I was going 5000° to the left when I was going straight ahead. Easiest way to see if that's the case is to read the live value with the wheels straight ahead - it should read 0° in that position, or close to. You might be lucky and it might be the connector - the sensors above your toes if you have a foot on the brake pedal. I had to araldite the section that turns to the column then reset.

 

[Ubique]

If you have the 4x4i screen, you can easily check the SAS with that, ABS activity 'faults' are not easy to track down because the system is often just reacting correctly to inputs, even if the input is erroneous.
If the SAS angle is correct, have a look at the wheel hub and driveshaft of the affected wheel, check for corrosion / lumps of rust jammed in or around the castellations on the CV joint.
It's possible it could be a defective sensor but I've rarely had to change them on L319's, they seem to be a lot more robust than the ones used by VWG, M-B, etc.

 

[tom2207]

As mentioned a good battery is a must , but it needs plugged in to read the codes and not to a 24 quid obd reader , you need to be able to get into specific live data , steering angle sensors seem to have a mind of their own , weve had a disco laying about for a year that the owner wont spend money on , last week it was towing a trailer about the yard for days without issue, then all the lights lit up, quick reset and recalibration of sas and no bother again for a few days , keep an eye on the traction and height too when the abs kicks in , as it tends to set the suspension down and turn off hill decent etc too ,,, all part of the fault finding game

 

[jmp49]

I usually plug/unplug a few times to clean the contacts then washout with contact cleaner unless you can see a heavy build up of crud then my favourite weapon is a glass fibre pencil to clean them off.

I have a trusty can of Deoxit D5, I got into using it for IC's and IC sockets on vintage computer's and consoles and arcade stuff because fixing old ones is a bit of a hobby and its common to find furry ic sockets and chip legs and pcb's when a battery has leaked, and its since migrated to the workshop on regular occasions to improve loom plug connections and stuff. I use the glassfibre pens also, enough to buy one that you can change the grp inserts on because they wear down quick when doing a larger area like a pcb. My process is hit it with the dexoit, replug for a few cycles, then if it looks good flood it for the final insertion.

Dexoit D5 is expensive, but you only need one can a decade in average diy use...


Stuff like bulb holders etc, I use a dremel with a grp brush in it.

 

[reb78]

As mentioned a good battery is a must , but it needs plugged in to read the codes and not to a 24 quid obd reader , you need to be able to get into specific live data , steering angle sensors seem to have a mind of their own , weve had a disco laying about for a year that the owner wont spend money on , last week it was towing a trailer about the yard for days without issue, then all the lights lit up, quick reset and recalibration of sas and no bother again for a few days , keep an eye on the traction and height too when the abs kicks in , as it tends to set the suspension down and turn off hill decent etc too ,,, all part of the fault finding game

Sounds like the little plastic disc that turns the sensor relative to the steering column is intermittently coming loose perhap?

 

[ajlelectronics]

Dexoit D5 is expensive, but you only need one can a decade in average diy use...

Shame about the grey on black, but cheaper here: https://www.ebay.co.uk/itm/12628344...meNywabo+6xRERNSVg3yz013Pw==|tkp:BFBM0q2A66pl

 

[Beanwood]

Interesting stuff chaps - yes the suspension dropped as well. Small steps - recalibrated the SAS seems to have helped. Battery is a little low- so it is on charge to see if that helps- but a couple of runs up and down the driveway with no issues yet. Trying it out later on today hopefully
Grp pen looks interesting.

 

[reb78]

The brake switch can be to blame for a lot of errors that result in suspension drop, limited to 50mph and no special programmes type messages. Doesn't sound like it in your case as I don't think that usually causes the abs to kick on.

 

[tom2207]

Sounds like the little plastic disc that turns the sensor relative to the steering column is intermittently coming loose perhap?

they do that from time to time , also if they are not lined up on assembly ,,, I use wurth gasket maker on them and that issue isnt an issue any more ,,, I also drill a couple of exta holes in the hidden part of the dash and drop out the shin protector , then anything in that space , like the brake switch reset or the pedal pin retainer becomes a whole lot easier , then the outer trim panel covers the extra holes ,,, keep it in mind and thank me later.

 

[Beanwood]

Thanks chaps. Deoxit and the brush appear to have cleaned the contacts sufficiently well that I have resolved the airbag light which was going to be an mot fail. Reset of the steering angle sensor seems to have resolved that as well. Just need to get it in for an MOT now, as I think regularly running and driving it will stop it rotting away.