96 cabrio possible electrical prob?

Cap, rotor, wires, plugs! But my bets on the ignition coil!

Which would do nothing to explain the clock getting reset. That and the coil's not exhibiting the usual signs. It doesn't arc or otherwise misbehave when dampened with a hose during 'dry' conditions. It would seem wasteful to replace it if it doesn't show signs of needing it.

Likewise the wires, plugs, cap and rotor are all new AND did not affect these symptoms on their replacement.

clock resetting only when cranking? If so battery could be a bit weak and the voltage is dropping off when under load of the starter.

Except that it's reset on entering the vehicle, not after cranking. It just spontaneously resets itself for no apparent reason. The battery's about a year old, being a replacement for the factory ('96) battery.

Thus why I'm wondering if there's some non-obvious location that's known to have moisture or corrosion issues. Something that might affect fuel delivery such that it'd cause the starting problems, while also possibly be involved with the clock getting reset. Some vehicles have known trouble spots, any come to mind on a cabrio?

-Bill Kearney

I was looking at a '96? Passat that had multiple problems. No sunroof power, interior lights, trunk light, power door locks and the no clock nor power to the speedo cluster with the ign off. I found a bad power door lock module causing 1 fuse to blow. I disconnected the module and replaced the fuse. Now everything else is working fine again.

So how do your door locks function? Does anything else have a problem?

disconnected

Door locks have been fine. It doesn't have keyless entry though; if that matters. I'll have to double-check whether or not other things lose their power when the clock has reset. Trouble is I'm not sure under what specific circumstances the clock has been reset. The symptoms are it's hard to start when it's wet outside and sometimes the time on the clock is wrong. The clock has never been wrong without the starting problem, but it has been hard to start without the clock having been reset. Thus I'm given to imagine there's something that's causing the hard starts to /sometimes/ also influence the clock. Likewise, the radio's security code does NOT GET RESET, so it's apparently not a system-wide power outage going on here.

Bearing in mind, of course, that at no point is the cranking effort affected. It always cranks at it's usual rate, it just won't catch. And since there's plenty of spark at this point I'm left wondering if it's something electrical affecting fuel delivery. And since it only occurs when wet outside I'm really wondering about water pooling up somewhere.

And since it's difficult to debug you can imagine why I'm hesitant to let the $tealership rob me blind wasting time only to not find it.

-Bill Kearney

Is your car equipped with an immobiliser?

It could be a local power outage :) It sounds like a broken "standby power" wire to me.

There are several power busses in your car. One of them is a "permanent

+12V", which is "hot" all the time and provides the "standby" power for the instrument cluster, engine ecu, central lock, radio etc. The only way to stop the clock is to disconnect this wire. It can as well corrupt the engine ECU memory settings, which would explain the difficult start.

If I was you, I would take a good look at this wire. There are several places, where it "branches", the most suspectible is the area under that plastic cover near the front window.

If the insulation is cracked somewhere and the water gets in, then there is a good chance, that the copper is corroded inside the insulation.

It is not an easy job to find it, as this wire runs inside of the loom, and you will need to unwrap the loom at every "branch" where this wire branches too, then locate the wire by the color and check the connection where this wire splits. The problem is, that it will look just fine from outside, and the only way to find the problem is by pulling the wire.

For starters you could just wiggle the wiring loom at every branch and see if the clock gets reset.

I would be hesitant too. Your car is likely to perform just fine when at the dealer :)

No. Just the regular door locks and factory door entry alarm. And there have been no issues of any kind with the alarm (now or ever).

That's the sort of thing I'm looking for. I wonder, does the clock and ECU feed from a different point than the radio? As in, further down the line from where the radio connects? The radio never loses power (doesn't reset itself) so I'm guessing it's not a 'vehicle-wide' power failure. If the clock and ECU branch off from the main buss at the same, or nearly the same, point on the buss then I could narrow my search quite a bit.

Is there a way to check for ECU memory corruption? Is there something the dealer could check, possibly out of the ordinary checks, that would show something like this had happened recently? As in, something I could tell the nitwit at the service department to specifically check and save them from a bug hunt (at my expense) in entirely the wrong direction?

Under the dash inside the car or up in the engine compartment? Which cover?

Yes, I've seen that sort of corrosion before in other vehicles. Front-end harness connections for headlights, power window sockets and the like. Not in a VW but in older jeeps and a 68 coupe deville. I recall an old '80 Scirocco of mine that had similar issues with corrosion caused by a front-end clip job whose weld started to fail (after 6 years). This sort of thing can be a devil to track down. But knowing the 'obvious' places to check helps a LOT.

Yep, good advice!

At this point it's a clusterf'k just trying to get an appointment with them. Always busy when I call and then they only call back when they seem to know it'll go to voicemail. Run around just trying to get a damned appointment. And this is with TWO different $tealerships.

-Bill Kearney

Yes, it is not just a single wire running around your car, there are several places where it splits and goes different directions. And those places are the most likely points of failure. I could look it up in the wiring diagrams when I get home.

Not really. The engine ECU has at least two sources of power: standby and the "ignition" (when you turn the key). It is impossible to predict (without knowing the ECU internals) what ECU will do, if it gets only the "ignition" power without the standby.

For example, ECU of my Vento/Jetta3 (1.8 Monomotronic) in this case starts the engine as usual, but then injects some 50% more fuel as needed (black spark plugs and ~50% worse mileage) and refuses to talk to the diagnostic equipment. The dealer was clueless, "your ECU is gone bad, 1000$". The funny side effect is, that the mileage shown by MFA was ~3 times as optimistic as it realy was :)

As you see, the behaviour of the sick computer is far from being obvious.

I dont think you succeed. Either he will know what to do himself, or it will not listen to you at all.

I ment the engine compartment. But the point of failure could be under the dash as well.

I will look at wiring diagrams if I not forget.

Is there a copy of the wiring schematics for a 1996 Cabrio online anywhere? I can read schematics.

I more along the lines of what error codes or other conditions might be present that would indicate a power fault.

Oh I can imagine. Thus why I'm also interested in pinning down this problem BEFORE it gets to the dealer. No sense in having them see one code, fix that, bill me, not fix the problem, bill me again, etc...

I can be, shall we say, persistent.

Thanks!

Sometimes :) But usually not for long :(

I just looked at what I have, and found the schematics of the american Jetta3 '96. It is not the same, but I don't expect it to be dramatically different. In any case, it's not complicated. The power wire goes from the battery to the fuse box under the dash first, and is distributed from there. The instrument cluster is connected directly to the box, and gets standby power through the fuse No. 21. If you pull it out, the clock should dissapear.

So, if the clock resets itself, it could be due to some internal error of the instrument cluster controller (unlikely) or due to the temporary loss of power, which can happen either inside the fuse box ("oh shit") or somewhere between the box and instrument cluster (a separate loom, about 2 feet long, easy to find).

The radio is connected through the different fuse and loom.

Is your mailbox functional?

It would be too simple, isn't it? :) According to the ancient embedded tradition (we are lucky that nobody patented it :)), the RAM is marked on initialisation with some magic pattern (0xAA 0x55 for example). The first thing the CPU does after it awakes from the sleep, is to look for this pattern and reinitialise the memory, as it was corrupted. No point of flagging an error, as it happends every time when the power to the ECU is restored. Things get much more interesting, if there was a partial power outage, say drop from 12 to the 5 volts for the short amount of time. It could be enough to just flip some bits in memory, but not everything. So, the CPU reads the correct pattern and sincerely believes the whole memory is OK, hence no error too :)

In any case, the "sick ecu" scenario was just a wild guess (one of many possibilities) and not necessary the case in your cabrio.