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Discussion Starter · #1 ·
I've recently brought a 2009 VW EOS 2.0 TDI CR. I've done about 1500 miles in the car trouble free but this evening while driving it felt like the engine cut followed by 3 beeps and then continued. About a mile later the car did the same but was able to quickly look down at the dash and spotted the red steering wheel light come on and then go off and the car continue OK.

When I got home I gave the car a few revs and as the revs came down the ABS, ESC and tyre pressure monitoring lights would come on briefly and the brightness of the text display dim and brighten again as the other lights went off. I was able to repeat this a few times

The other weird thing we've had twice is the climate control. The fan works fine but the climate control will then not enable the fan. The climate control is on but no fan speed is shown. You can manually turn the fan speed down and the climate control will turn off and climate control comes back on as you turn the fan speed up but still no fan speed is indicated. If you turn the car off and restart it all works fine again. I've only experienced this when the AC is running and not at the same time as the other issue. AC blows cold across all vents.

The battery doesn't seem very strong measuring 12.1-12.2 at rest but we've had 0 sign of any starting issues. I need to check things with a decent meter. OBD reader reads a very variable voltage at the ODB device when the car is running, but I don't trust its reading, I've had issues before with it.

I've searched but found nothing on hear/google except steering rack or ABS sensor issues but it seems odd to have all these things at the same time. Any help appreciated. I'm leaning towards some electrical gremlins, possibly the weak battery maybe alternator causing issues but I want to confirm this with a decent meter. I've seen no sign of charging issues indicated by a warning lamp or in headlights etc.

I've read the codes using a generic code reader but no codes are found.

I've since been out for another drive this evening and had 0 issues.

The car is in the garage next week as I did notice a small split in a outer CV boot, so will ask them to have a look over at the same time.
 

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The symptoms you describe suggest a power failure and why you don't see any fault codes on a V.W compatible tool (?). If you disconnect and reconnect the battery, the steering warning lights come on then go off after a few yards as the steering module re-calibrates itself and isn't usually shown as a stored steering fault. Measuring battery terminal voltage doesn't tell you if it's a strong battery or has an intermittent cell failure.

If the battery age is unknown or older than 3-4 years, change it first. Check the battery clamp terminals and wiring to the ground terminals are clean. The next possibility is the ignition switch and finally there have been some reported problems with burned out fuseholders in the main ABS fuse box causing a loss of vehicle power whilst driving.
 

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I would go with Vox. I've just swapped my battery out despite it not showing any specific faults on a test, as I have had a couple of low voltage warnings this week.

For the sake of 70.00 worth trying as that will either fix the issues or at least put aside any queries over the battery being the problem.
 

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Discussion Starter · #4 ·
Thanks for the replies. I'm leaning towards electrical.

I did a little more testing this morning once I had found my meter. The car sat overnight and the battery at rest after unlocking the car and opening the bonnet measure 12.55v.

The positive battery terminal does have a dusting of the start of some corrosion, very minimal but will clean up. Under load the terminal post and vehicle cable measure the same voltage so indicates minimal resistance between cable and post.

2 conflicting findings. With the engine running the highest voltage I had across the battery was 13.6v. Following a few restarts I also had 13v and once had 12.6v. Each time the engine was allowed to idle and then the revs increased and held at 1500. This makes me think alternator. However here's the conflicting bit. To measure the battery under load I first turned the ignition to the on position, set the fan blower to max and then turned on the headlights and fog. Very briefly probably less than a second I 100% had the dash go out and I'm 70% sure the blower also quit. It was very quick and only once and when turning on the headlights. I then measured battery voltage under load and it was 11.8/11.9 which seems OK considering the load.

So I'm thinking battery or body ground connection? clean that battery terminal up for sure.

At no point have I seen a charge warning light on while driving, I stupidly forgot to check when I measure 12.6v with the engine running, I had the wife in the car following instructions so I could monitor under the bonnet.
 

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Battery terminal voltage isn't a good indicator of battery condition. You have to measure the battery terminal voltage drop for a fully charged battery on the highest load, which is whilst cranking the engine with headlights on. Headlight load isn't 500 Amps cranking!

If your battery tests o.k on a cranking load, I'd start looking at and under the fuse box at wiring and fuse holders. There's also an important chassis ground connection hidden underneath which you haven't found yet. If you were using decent V.W compatible diagnostics you might get back more information about system voltages? If you have a shop manual with wiring diagrams you can relate your symptoms to the power lines feeding those parts and reach some conclusions where to start looking. That is a far better way than guessing with a voltmeter. The main engine bay fusebox is where all the high power stuff starts and contains the power bus nodes feeding smaller fuses in the dash end.

The posts I read of ABS fuseboxes failing started like yours. A main fuseholder contacts have got dirty and high resistance. As high current passes the fuseholder heats up, contacts lose their spring and heat up even more to red heat until the ABS plastic starts melting away. I think you will be getting some plastic smell before the plastic self destructs.

Raised engine rpm can be misleading because the ECU increases rpm when the aircon compressor cuts in and when the alternator is charging hard. If your battery terminal voltage makes about 14.5 volts at 1500rpm, the alternator is charging. You said you got 13.6 which you should only get if the battery was at max. charge? Leave the headlights on for 5 minutes, start the car and recheck. Those voltages and confirmation of alternator charge are about right for a good battery, but you won't get the same with a dud battery. If you want to make the choice between replacing an alternator and changing the battery, do what we suggest and replace the battery first.
 

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Discussion Starter · #6 ·
Thanks voxmagna. I do apricate you taking the time to reply and sharing your experiences and knowledge.

I'm hoping I may have found the issue. The charge voltage across the battery terminals was 13v, measuring the negative battery cable from chassis to battery I measured a 0.8v drop. I'm hoping the negative battery cable is the issue. The ends were clean and making good contact so I can only assume an issue with one of the crimps.

I was able to go out and take a cable off VW Golf at a local scrap yard. VW didn't have one in stock. I'm now seeing between 13.6 and 13.8v across the battery.

I only have access to basic test equipment and data, this is also my first VW. I did have a look in the under bonnet fuse box and everything looks clean, dry and in good condition.

Nice weather this evening so when for a drive with the roof down and AC on to simulate same conditions when I had previously experienced problems and had none so far.

It may be psychological but the starter sounds like it spins that little bit faster now when starting the car. 🤞
 

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If you suspect poor terminals, connect your dvm between the battery negative post and chassis metal then measure the voltage drop whilst cranking. Repeat with the DVM connected between the battery positive terminal and the starter positive connection. Lift the lid on the engine bay fusebox, turn the lights on and measure voltage drops between battery positive terminal, the fusebox incoming busbars and the output side of each fuse.

You can't check the ground terminal hidden under the fusebox without disconnecting the battery and removing the battery tray. From memory, that's the important common ground point for all the brown loom wiring NOT the easy to see ground terminal which the battery negative attaches to.
 

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Discussion Starter · #8 ·
If you suspect poor terminals, connect your dvm between the battery negative post and chassis metal then measure the voltage drop whilst cranking. Repeat with the DVM connected between the battery positive terminal and the starter positive connection. Lift the lid on the engine bay fusebox, turn the lights on and measure voltage drops between battery positive terminal, the fusebox incoming busbars and the output side of each fuse.

You can't check the ground terminal hidden under the fusebox without disconnecting the battery and removing the battery tray. From memory, that's the important common ground point for all the brown loom wiring NOT the easy to see ground terminal which the battery negative attaches to.

Thanks.. I will have a look at that earth too, and the various voltage drops in the engine bay fuse box. I also want to check the earth between the engine and body.

The battery to body ground is right next to the battery, that's the cable I swapped out yesterday.

Again, thank-you for replying.
 
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