Bad Alternator? Voltage drop?

[beale187]

I would try making an extra earth lead from the battery to the engine and connect it to the mounting bolt on the starter motor and see if that makes any difference...i spent months with issues relating to possible starter motor,altenator, battery and ignition switch problems that turned out to be the earth lead and its been fine ever since...

Funny enough i checked out my donor Bora and the previous owner had done exactly this!

[Bora Sport]

I wait to be proven wrong but it still sounds to me like the alternator isn't charging enough.

[beale187]

I wait to be proven wrong but it still sounds to me like the alternator isn't charging enough.

That's my guess as well... I'm just avoiding jacking it up and pulling the front off to do the job haha, when you live on a hill just jacking it up safely is a pain in the a$$

[beale187]

Quick update.

Since installing another battery there's been no issues starting the beast. However all the other symptoms (cluster flickers, headlights dim when operating windows, humming noise through CD players etc..) are still there.

Pulled the front off over the weekend to get access to the alternator. Hooked up the voltmeter to the B1+ nut on the alternator and the negative post on the battery. At idle and under load (all accessories on) I started with a reading around 14.1v (seemed to fluctuate between 13.8 - 14.2) but it slowly dropped to around 13.3v (I assume this was because the battery had reached full charge?). So I took the rpm up to 3,000 and got a fairly consistent 14.2v reading.

So two quick questions if I can.

Given all readings are around where they need to be is it safe to say the alternator is ok?
AND I have a list of ground points that I need to check around the vehicle, some of which are not easy to access. Can a bad earth in one circuit effect another unrelated circuit? For example; If I have a loose earth connection for a door control module, can this bad earth effect headlights, cluster etc..??

Give me nuts and bolts any day...

[mikk]

Yes, check wiring everywhere. Could it be a short somewhere?

[JustCruisn]

Check where the big fuse links are on top of the battery, the ones with bolt each end. If these get loose you will see voltage drop, or worse a fire. Main line from alternator comes into one of these fuses, 120Amp I think.

[beale187]

At first I thought it could be the alternator (still could be). But the flickering cluster, headlights dim when using windows (and when braking), the humming noise through the stereo which changes pitch with RPM... All indicate a loose wire or short somewhere.

I've checked the grounds under the battery tray and that connect to the top of the gearbox, they're tight and clean...

[beale187]

Check where the big fuse links are on top of the battery, the ones with bolt each end. If these get loose you will see voltage drop, or worse a fire. Main line from alternator comes into one of these fuses, 120Amp I think.

They all look good... Pulled all the fuses in the cabin as well

[beale187]

Ran VAG-Com this morning, here's the results.

6 Faults Found:
17925 - Power Supply Relay for ECU (J271 or J363)
P1517 - 004 - Electrical Malfunction - Intermittent
17457 - Bank1; Exhaust Cam Adjustment Valve 1 (N31
P1049 - 002 - Short to Ground - Intermittent
17935 - Camshaft Timing Adj. Bank1 (N205)
P1527 - 002 - Short to Ground - Intermittent
17949 - Fuel Pump Relay (J17)
P1541 - 004 - Open Circuit - Intermittent
17923 - Intake Manifold Valve (N156)
P1515 - 002 - Short to Ground - Intermittent
17607 - Oxygen (Lambda) Sensor Heater Circuit: B2 S2
P1199 - 008 - Electrical Malfunction - Intermittent

On the circuit diagrams I have, N318, N205 & N156 all appear to share a common earth connection which appears to be for the engine wiring harness. Am I right in thinking if I trace this back to where it grounds on the body of the vehicle this could be the culprit?

[beale187]

EDIT: 17457 - Bank1; Exhaust Cam Adjustment Valve 1 N318

Not cool face.... Definitely not cool face.

[beale187]

Anyone know where this relay is located in the engine bay? J59 X-Contact Relief?

[beale187]

Any suggestions on the auto electrician here in Sydney that's familiar with VW's?

After weeks on this thing I phoned VW liverpool this morning, only to be told to look for an Auto Electrician

[BoraBora]

I had a similar experience with the dealers. Mind you their argument did make sense. They said their senior tech was 12 when mkiv's came out.. this was in relation to haldex servicing, their point is still valid though. So an auto elec or mkiv mechanic is probably a better choice.

[beale187]

* UPDATE & SOLVED *

Perfect case of looking at a problem for too long me thinks

So even though I had checked this cable was tight and clean I hadn't actually ran a multimeter across. Had a mate visit with a current sensor and found the problem within 5mins!

There's small post (left) on the positive lead that connects to the fuse box (on top of the battery). The nut and thread was completely shot. You can see in this pic it's completely rounded off





Solution.... Swap it to the other side!



Eventually I'll get around to changing that positive lead or I may just run a tap and tie on the post and nut but for now it's fixed!

Big cheers for everybody's input.