Breezy_Pete

I'd be quite wary of fitting an AGM battery without modifying the charging system. Cars with those batteries tend to have charging management systems that deliberately keep them at a state of charge about 20% below maximum. Many people on here will tell you that this is to leave capacity space for 'micro-hybrid' boost charging on cars with variable voltage alternators, but I suspect it's at least equally because of possible problems with overcharging. See BU-201a: Absorbent Glass Mat (AGM) - Battery UniversityBU-201a: Absorbent Glass Mat (AGM) - Battery University Also they are not keen on getting warm. Here's a quote from that page: As with all gelled and sealed units, AGM batteries are sensitive to overcharging. A charge to 2.40V/cell (and higher) is fine; however, the float charge should be reduced to between 2.25 and 2.30V/cell (summer temperatures may require lower voltages). Automotive charging systems for flooded lead acid often have a fixed float voltage setting of 14.40V (2.40V/cell); a direct replacement with a sealed unit could overcharge the battery on a long drive. (See BU-403: Charging Lead Acid.) AGM and other sealed batteries do not like heat and should be installed away from the engine compartment. Manufacturers recommend halting charge if the battery core reaches 49°C (120°F). Table 1 spells out the advantages and limitations of AGM.

No harm in trying though.

There's plenty of melted plastic around too, now that I look again at your photo.

It's the one in the second picture. Look at how the copper strand ends in the crimp terminal look corroded, in comparison to its neighbouring cables. As does the captive nut. Yes 16mm squared conductor cross-sectional area is specified in the wiring diagram. Automotive cables often have a deceptively thin outside diameter in relation to the conductor CSA. Thin insulation.

Then I would inspect belts, but unless they look terrible, just drive the car.

Sounds cheap compared to here, but possibly doesn't include water pump at that price? I paid £350 7 years ago at a UK VW dealership, and that was a special offer. Did include WP though.

Inspect the belts then, as a minimum. How long into the future do you hope to keep the car?

16mm² on the wiring diagram, but no harm in going thicker. M8 crimp at alternator end, M6 at fuse end. See what a local car parts shop has or can make up for you. Measure length and don't make much longer.

The alternator positive cable may be bundled in with some other cabling, but you could just replace the high current thick cable, disconnecting both ends of the old one, leaving everything else in place, rather than replace the whole alternator loom. I'll check the minimum mm² size requirement of that cable for your car, one moment.

Great work. I think that means the alternator is probably not at fault. Yes, I think your conclusion is correct, provided that there is no loose or dirty connection between battery positive post and the fuse.

If the alternator does manage a 'good' voltage (when measured at the alternator) at higher rpm, changing this positive cable out may well be helpful. Do check that the positive battery clamp isn't loose (or dirty) on the battery post first though. Also the connection onto the underside of the fuse tray, though that is well protected from the weather and has probably never been undone.

Yes, but see if that improves if you raise the engine rpm (assistant probably required). If the battery is taking a very high charging current, it may be more than the alternator is capable of generating at idle rpm. This is one reason it's good to do the testing with a known good battery in place.

There's a plastic cover over the upper portion of the timing belts that releases with just two metal clips if I remember rightly. Remove and inspect visually (photograph and post) , though you may not be able to tell very much from that. These are about 7 years old, I think, and maybe 40-50k km since fitting.

Does the pre-75k record include a timing belt change? And how many years ago was that 75k reached?

No, that's not bad actually. If you can reach the positive output connection on the back end of the alternator without danger of shorting the probe to other things, try measuring volts between there and battery positive with the same loads on. That will measure total loss in the positive wiring.

^

That's a fuse. Good to have clean connections to it, but I'd actually expect the earth connections from alternator to battery negative to have more losses. With everything connected and some current consumers switched on, measure voltage between battery negative post and alternator case metal (scratch through any corrosion to clean metal). This will give a direct reading of losses in the earth path. Sounds like you're losing far too much voltage between alt and battery.

Check for a further character beyond the 601 on the disc. Also, see what it says after "min".

Assuming the car doesn't have "mountain driving assist" (HHC), you're looking at a permanent 12V supply from e-box fuse 16 via a red/green wire to pin 1 at the module; another from fuse 4 via a red wire to pin 32 at the module. Both of these fuses are 30 amp rated. The e-box is the engine-bay fuse/relay holder. An ignition-on supply comes from fuse 2 (5 amp rated) in the cabin fusebox via a black/grey wire to pin 4 at the module. This one will only be at 12V with ignition on obviously. Earth connections to the module are at pins 16 and 47. Verify that all these are intact before spending any more on parts.

The problem with the present one may be something external like a blown fuse or broken wire, I've seen a few threads where such a wiring fault caused this communication error, including a recent one. I would disconnect the connector from the module and methodically start to check all supply connections. I'll research pin numbers for you now. You may well see a part number on the ECU/module near to the connector,

I don't think I understand the two systems well enough to advise you on all the differences, but the two parts diagrams show AXR having a 'throttle body' upstream of the EGR (item 3 here vacuum system; exhaust gas recirculation - Fabia(FAB) [EUROPA 2005 year] (7zap.com)). The ATD engine doesn't have this, but instead has a solenoid valve additional to the vacuum block (item 10 here; vacuum system; exhaust gas recirculation - Fabia(FAB) [EUROPA 2005 year] (7zap.com)) Note that this additional solenoid is described as N239 in one of the columns of that table. The wiring diagram section that covers both looks like this: and the * next to N18 is defined as "only on models with engine code ATD". I wonder if that's an error, and that asterisk should be next to N239 on the diagram instead of N18? That seems to make more sense, I think. What are the wire colours that you have, and which pin numbers of the 6-way connector do they come from?

You need to measure the resistance of each wire between ECU connector and valve block connector. Close to zero Ohms is what you hope to see. Unless you know that the wires have good continuity, it's difficult to know if the voltage at the valve block is 0V because the ECU is switching the valve fully on, or because there is no connection because the wire is broken.

Can you borrow another battery from a friend briefly, to see whether that changes things? Try measuring the alternator output voltage right at the alternator, to see if you are losing some in the cabling. Negative meter probe on a scraped clean bit of alternator casing, positive on the output connection (careful not to short that probe to any nearby metal). 14.0 seems a little low, but the alternator setpoint is temperature dependent, what's the ambient temperature in your area at the moment?

Yep, and not just during regen operations for fire control. Any time the engine management wants more EGR flow (for NOx reduction) than could be achieved without this throttling of intake airflow.

M9 x 1.25 if it's the 256mm disc set-up, I believe. Various other repair options including helicoils, press-fit threaded inserts etc. all easily found on ebay.