electrical issue - disc pad wear sensor involvement, an earthing issue? updated

[cc]

when driving thru rain at night on the highway to brisbane. The top right warning light on the check panel came on. For the low brake fluid and/or hand brake engaged warning. At the same time the speedo dropped back to zero. This became a puzzle for a few weeks after. Along with the engine temp gauge which would also indicate the engine running at 115 deg in suburban driving at between 2000 and 3000 rpm. Which it hadnt done before. In the subsequent weeks the same 'brake light would flicker on and off brightly v quickly or glow weakly while still flickering quickly or stay brightly on or blink on or off.. The speedo would be mostly resting on zero. I lived with this for a while as the brake fluid reservoir was ok, pads were good and the hand brake wasnt engaged.
On days when i thought the temp gauge was too high the interior heater was put on max (which didn't drop the gauge temperature.) Then the transmission warning light in the tachometer dial decided to join the party and the car would accelerate quite sluggishly. Along with the transmission light being on, the lcd display for PRN or D didnt correlate with the position of the gear lever.
In the weeks before the transmission light came on there was time to observe that when the brake warning light wasnt glowing the speedo worked more often and the temperature was at 90 most of the time. Also that the transmission warning light would come on with the brake warning light coming on.
Having read on forums that earth leakages were a common fault and the temperature gauge wasnt always a reliable indicator of the correct temp of the engine. Thought turned to the wire leading into the male plug end of the passenger side front brake pad wear sensor circuit. As the wires insulation was cracked next to where it disappeared into the plug. Had noticed it when replacing the suspension arms but not done anything about it. Just noticed that plastic insulation was cracked and that it had to be stretched to get the plug into its socket.
So off with the wheel and on with some red  electrical tape over the offending sensor wire. To stop the sensor wire being stretched more of the sensor wire was fed thru the grommet that attaches the wire to the shock absorber strut. I also unhitched the pad wear sensor wire from the abs sensor wire which had been incorrectly routed/interconnected like links on a chain. See 2nd pic  unhitched.
Since this repair the brake warning light has been mostly off. Engine temp has been good. The speedo works most of the time and the transmission is back to normal. Which is ok but not the end of the story.
After checking the owners manual it turns out the brake pad wear warning light isnt in the central check panel but in the speedo dial and it hasnt lit up yet at all....
Also the problem hasnt disappeared as the brake warning light is still occasionally doing its flickering thing.
The dodgy brake pad wear sensor wire may still be an issue as the plug was flopping about on the end of the wire and the copper core may have fatigued/broken and separated. The red electrical  tape is insulating it but may also be holding the broken wire ends together.  So will source a replacement wire and plug..
It may also be more than one electrical issue. Perhaps there is an issue with the abs circuit. The abs warning light hasnt come on tho. Dont know if it does if its a problem with the abs sensor at the wheel.
Wonder if the current flowing thru the earthing brake pad wear wire affected the signal from the abs sensor when the 2 wires were looped across each other. But the light for the brake pad wear wasn't on..
Can someone confirm that it is the passenger side front abs unit that supplies the wheel speed data that the abs unit processes before sending it to the speedo. cheers

[bazzbazz]

You definitely need to get a cheap laptop, a copy of MultiECUSCan and the appropriate adapters, will take MOST
of the guesswork out and make your Alfa life so much more enjoyable. 

Baz

[cc]

Hi Baz
Which is the most useful adaptor/connector for a march 2002 V6?.
I bought an OBDLink SX thru a place in Canberra, that  didnt communicate with the car. Sent it back and didnt get a refund....
Have been meaning to get into ecu side of things and the multiecuscan web site looks active and v good.
Have also been tempted by things electronic by the British  Pico automotive oscilloscope. See www.picoauto.com. Ths w/site has an interesting forum of case studies re the oscilloscope being used to diagnose in detail problems identified by codes from the cars ecu.
https://www.picoauto.com/support/forum50.html?sid=249ff1bde0665e095b2c5f44bce361ba

Also tempted by the Texa obd matrix made by the Italians. www.texa.com/products v exe but handy for logging data while driving.

Have  had a few days now with no electrical problems.
Went over to CL restorations for some trim screws for the bumpers 1/2 of the screws had fallen out or been damaged. Also an air con knob back light bulb.

The car has a lumpy idle, which i didnt know was typical or not. Savvas  at CL had a listen and thought it may be a coilpak.
The engine is developing good power when being driven.

The light bulb is a tiny thing and can also be sourced from Repco as an r286. The local repco had a dozen in stock.
cheers

[cc]

After 3 weeks of smooth running the hand brake warning light is misbehaving as before.
Just the occasional flicker as before. This morning however after adding 500ml of engine oil (and overfilling by 3 mm over the top mark!)
all the old symptoms have returned and the car is driving in limp home mode.
speedo dead, over temp dial, displaying incorrect gear info. ie indicating R when doing 40km/hr in D. Audible beep warning. Transmission fault icon occasionally.
What to do.. When in doubt dither! so have fixed blown speedo bulb!
Wonder if the hand brake switch circuit is on the same circuit as the abs...

a few hours later...

Thought i would get some value from my racq membership and called them up. The service man did a few diagnostics;
The alternator is supplying an appropriate amount of current.
The battery is in good condition.
No trouble codes on the computer.
The car is drawing 0.5 to 0.7 amps of current shortly after turning everything off.
Which may be ok as ive read somewhere the ecu still operates/ functions for some time after turning the car off.
A curious behaviour is that with the car ignition off. The dash lights stop flickering and the h/brake light stays off for longer when the headlights are on. Maybe the headlight relay is on the way out.

Have also observed that the back seat interior lights operate correctly on the doors opening. But cannot be turned on at all when pressing the lights oval lens.
So things to check are:
headlight relay.
fuse for rear interior lights.
Earth for i lights, also the electric windows that are in circuit with the interior lights.
The front brake pad wear sensor connection as taping this up 3 weeks ago stopped the electrical issues.

a few days later.. Almost all electrical problems have ceased! After observing that having  the headlights on; stopped all electrical problem symptoms apart from the speedo still occasionally dipping to zero speed.. This after using the car with the headlights on all the time.
What Im thinking is that when the  headlight wand on the steering column is at the off position it was slightly open circuit into the instrument cluster wiring loom. When the wand was switched onto the on position it no longer shorted into the instrument loom. The low beam relay is located on a bracket behind the glove box (see page 170 owners manual). Dont think it is causing the problem.
Earlier on in this post i thought correcting a dicky wire on the front left brake pad wear sensor circuit sorted out the electrical problem. Thinking back to this when i took the car for a test drive, it was at dusk and i switched the headlights on...
So im thinking the issue is in the electrical component for the headlight wand on the steering column.