Vag Com Problems

[alan_131]

Sorry I was being incredibly thick there, thought you were referring to the supply to the cluster. doh.. I see now why you were expecting the supply voltage to be more-or-less constant.

I'm guessing from your last post that for a while the problem went away (long enough for you to drive it till the gauge dropped below half). Is that right, and was it immediately after you'd been looking at something (he said hopefully).

Is it now back solidly? If it is,does it happen as soon as you crank, or as soon as it runs (appreciate might not be much time between the two).

Is the ecu still clicking with the instruments back?

[ianbin2012]

Ok, i lifted the kick guards on both sides front and rear everything is dry as a dry thing and all wires are solid and intact.

Yes it is back permanently, as soon as the engine is running the illumination lights in the cluster go on and off and the gauges flicker, when your driving the coolant -fuel gauge and rev counter flicker about whilst the speedo ranges from anything from 0 to 120 and anything in between.

When you turn on the side lights the cluster lights stay on although the gauges still flicker and the glow plug light and the air bag light are lit very dimly.

[biturbo.s4]

Sounds like a bad earth. Although still worth whipping the tape off the loom and recrimping the terminal.

[ianbin2012]

Which bad earth to check, there seems to be quite a few around the car.

I don`t know if it`s relevant but my washer controls work in reverse, instead of pulling the stalk towards you for wash you have to push it away.

Sorry forgot to say in last post that the ecu clicks when the cluster is connected but does not click when disconnected.

[biturbo.s4]

Please just put my mind at rest - Whip the tape off the loom below the passenger side belt pretensioner and pull back the tape over the two crimps, cut them back and then join them together.

It should be two lots of red/white wires connected together with one little poxy 0.5 red/white.

[ianbin2012]

Took tape off, plenty of wires but i can`t see the crimp`s you speak of or the small red/white wire.

Some of the wires run front/rear under kick cover whilst the rest go under the seat to the alarm/central locking unit.

[biturbo.s4]

Ahh silly me, yours must be a mk1 then??

I'd have to look at wiring diagrams and get back to you. :)

[alan_131]

Am I right thinking you have the clicking from the ecu all the time you're driving with the instrument cluster connected?

Do the panel lights go on and off to a regular pattern?

With your turbo problem, is there any change in what's happening on the instrument panel? Also, on the flat even with wide open throttle it's still fine, it's only on a hill this "power on, power off, power on" happens.

If you run the engine, then stall it (horrible I know) does the flickering stop & things go back to as if you'd just turned the ignition on?

If you turn the ignition on, then shake the engine, does anything happen at the panel?

If you connect to the engine with vcds, then start, does vcds stay connected / let you read measuring blocks (ditto instrument cluster)

 

I'm wondering if something is re-initialising the instrument panel, either a power/earth fault or the ecu. My favourite would be, as biturbo.s4 says, power/earth. Not sure how much the haynes manual for pre-98 is to be relied on for wiring diagrams, and that doesn't help.

Do you still have easy access to the fuel sender connector?

[ianbin2012]

First question, yes all the time when driving.

Second question, no the flickering lights and dancing gauges are random.

Third question, no cluster goes nuts all the time.

Slight inclines and hill`s power on/off happens.

Yes flickering stops and just as if ignition just turned on.

Haven`t tried shaking the engine yet.

With the vcds connected it will check everything on the car with ignition on and started but it cannot connect to the instrument panel i just get a clicking noise coming from either the cluster or the ecu.

I tried doing an individual check of the instruments but it kept coming up with controller not responding.

Back to the turbo problem i noticed whilst having a rummage around under the bonnet that allot of the vac pipes seem to be in a bad way, so replacing all of them tomorrow.

Ive put the carpet back down but it`s quite easy to get at the sender again.

[alan_131]

Does this sound right to you? Apart from the problem not connecting to the instrument panel controller, (and ignoring your turbo issue for a second) all of the jumping around sounds just like a shaky feed/earth. It happens as soon as the engine starts, so could also be a change in status of something inside the panel when engine running is flagged.

 

I need to visit my other Gal to check on the pre-98 build, it's a way away but I hope to be there tomorrow.

Is it possible for you to log boost and vehicle speed when driving on the stretch of road you have the boost problem on - if it logs fast enough and the power on/off cycle takes long enough you might see if the speed and boost are consistent or jump around and if the ecu is calling for reduced boost? Only a suggestion as it can be a pain to do when driving.

I asked about the fuel sensor because its earth links to the same point as the instrument panel according to haynes and I wondered if, with the engine running, there was a voltage between the earth side of the fuel level connector and a known good earth like the floorpan. As it's a small gauge wire I want to be cautious before seeing what happens if it is jumpered to the earth point.

If I can get all the junk out of the back of mine I'll see what I get.

 

Did you get a chance to test battery voltage - might also be interesting to see how that compares with vagcom's reading if you should happen to have it connected, and how close it is to the voltages you measured at the fuel level sender plug engine off.

[ianbin2012]

I would have a hard job to log the boost whilst driving as i used my desktop pc in the car to use vcds whilst the car was stationary if i wanted to use it driving i would need a hell of a long extension lead.

Still havent had a chance to check battery voltage.

Do you think it may be worth grabbing a set of clocks and trying them to see if it still happens.

Do they have to be tdi clocks as they are quite hard to come by?

Edited July 30, 2012 by ianbin2012

[alan_131]

Know what you mean about the extension lead - my partner is the one with the working laptop battery so the only time I can test is when she's not using it.

Maybe a socket in the centre of a field and driving round in circles?

 

I think a non-tdi panel might work just for testing, though not so good long term - even if all else is the same, the clocks are a bit different for the higher revving engine I would think

I want to try something quickly on my '97 car if I can get there today. edit - I didn't. If you like, can lend you the clocks from that for testing if not cracked soon and you can't find a set locally

Hope the vac pipe change helps the turbo problem.

Thought I'd posted this this a.m.

Edited July 31, 2012 by alan_131

[ianbin2012]

Thanks for the offer of the clocks but i think i can get a set from the local scrappy for a tenner.

I got the vac pipes from a local diesel/petrol specialist the type being motorsport silicone tubing 3.5mm and 5mm 2 metres of each for a grand total of 7 quid, thats a saving of 127 quid as quoted for the same stuff from frauds.

They recommend this stuff as it withstands temperature and increase/decrease in pressure better than the cotton/rubber tubing and it`s also cheaper.

I will get a set of clocks as soon as i can and will let you know what happens.

[ianbin2012]

Problem sorted, picked up a set of seat alabama tdi clocks from scrappy today plugged them in job done, they are a bit different from mine as they have the bulb failure/door open panel but they work.

Only thing is know the airbag light is on(oh joy)more head scratching.

So if your clocks are playing silly buggers try a cheap donor set first, saves alot of swearing and head scatching.

Thanks for everybody`s input, information is a good thing.

[ianbin2012]

Little bit premature with the celebrations, took car out for a drive speedo is far from accurate registering 60 when doing 30 also airbag light on, washer fluid level light on and battery light dimly glowing apart from that illumination lights dont flicker and no clicking from ecu.

If i wasnt confused i`am now.

[ianbin2012]

Right had a look through a lot of posts and came across one that mentioned the big round multiplug on the front of the block as quite a few wires run through it, anyway popped the bonnet and had a look and instead of different coloured wires looking at me i could see plenty of copper, most of the wires had rub marks on them exposing the copper core.

Most of the wires are going to the components that are causing my faults.

My next plan of attack is to strip down the wiring and re-solder/heatshrink the lot and fingers crossed it will hopefuly cure the problems.

[seatkid]

That'll be the cause of the MAF go/no go power problem....

[alan_131]

Well seems to me you've pretty much cracked it! I think your find will explain a lot. Apologies for the pause. I've been through both my '97 and '99 cars and as far as I can tell the red plug is functionally identical in both. Measured all the voltages and they are the same except abs related. Both behave the same re when the illumination comes on. Not sure what model year the '97 is, but the black moulding that attaches to the raw steel bracing bar across the front of the dash is dated april '97. So sorry, not quite the match I was hoping for for comparison purposes

 

Took the red cover off the plug, and tried to simulate your fault as it was by popping various pins in the plug - couldn't exactly, as I think yours is intermittent due to engine movement/vibration, but I did get washer level (and some of the time main beam warning) when I had pin 3 (earth for sidelights) out and sidelights on at the switch (effectively same as yours)

I was going to suggest you checked the voltages on the plug, and maybe for elimination purposes provide alternative feed/earth, but I really don't think there would be any point until you've sorted out your find.

 

If you do want to check voltages later, the most relevant ones are i think pins 11(red) and 13(black) - should be steady at around 12v ignition on. I measured using a probe jammed against the brace for earth.

Earths are pins 1&3 - brown -plus via bulbs(eg washer level) etc if it can find a way...

Hope your rework cracks it.

Afterthought-

The Haynes manual gives the switched feed as on pin 22 - it's actually on pin 13 on my cars anyway.

 

Vehicle speed sensor apparently earths through same point as instrument functional earth. Really think when you've fixed your earths, anything left will be pretty easy to find...

Edited August 2, 2012 by alan_131