OBD port stopped working, I think....

[HPsauce]

It's a while since I did a VCDS scan and my S8 has also been on SORN for a few weeks.
While unused I plug a (sizeable, motorhome model) solar panel into the OBD port to give a minimal trickle charge to the battery.
I didn't think much about it but the battery was too low to start the car the other day; I had to put a proper charger on overnight.

Today I decided to do a VCDS scan as I'm off on a reasonable drive tomorrow (Goodwood) but VCDS said the cable wasn't plugged in, when it was (and felt like it was).

This suggests to me that the OBD port isn't properly connected or connecting. Before I take the drivers knee panel off to investigate are there any fuses or connections elsewhere that are worth checking first?

[steamship]

Originally Posted by HPsauce

This suggests to me that the OBD port isn't properly connected or connecting. Before I take the drivers knee panel off to investigate are there any fuses or connections elsewhere that are worth checking first?

Only discovered the forum working again, so it may be too late for you. I found that sometimes the VCDS cable can seem plugged in and snug, but it fails to work. When checking the light on the cable, it's been orange, so I just reseat it and it works fine.

As for the fuse, it's fuse #9 on the top row of fuses in the drivers footwell. It's a 10A fuse.

[HPsauce]

Thanks Sean I'll check the fuse first. I reseated it several times.

[HPsauce]

Originally Posted by steamship

As for the fuse, it's fuse #9 on the top row of fuses in the drivers footwell. It's a 10A fuse.

Correct.
So how could this happen?



PS Weird thing I found about the fuses/spares.
The spare 10A fuse in the bottom (spare fuse) row was identical to that in shape and fitted fine. Ran a VCDS scan to verify.
But when I went to my backup fuses to replenish the spare slot it wouldn't go in there. On examination the blades were closer together and the spare fuse slot has a wide separator.
BUT the backup fuse fits fine in the "live" position so I fitted it there and tried VCDS again (to check), returning the original (probably OEM) 10A fuse to it's spare slot.
PPS Though when I went back to my backup spares and checked them all, they appeared at first glance to have the same gap but then I noticed some had blades with the sort of "knife edge" you can see on my blown 10A one (leading and inner edges) and some were just square cut. So maybe that's the subtle difference?

[steamship]

Originally Posted by HPsauce

So how could this happen?

Exactly, considering that the fuse is supposedly 'only' for the diagnostics port.

Originally Posted by HPsauce

But when I went to my backup fuses to replenish the spare slot it wouldn't go in there. On examination the blades were closer together and the spare fuse slot has a wide separator.

I've never checked mine to that degree, but of the few different ones I've bought over the years, what I've noticed was the shape of the fuse 'wire' itself, and subtle differences in the dimensions of the plastic holder. Usually if I'm trying to remove a fuse with the little tool provided, and sometimes it won't grip properly.

[HPsauce]

Originally Posted by steamship

Exactly, considering that the fuse is supposedly 'only' for the diagnostics port.

However I do plug my "battery maintainer" solar panel in there too, so it almost certainly has to be something to do with that. I must have shorted something out somehow, though given the design of the leads and connectors I really can't see how.

The panel and leads test out fine with everything I can logically think to try!
There is a junction in the lead to allow different termination connectors (e.g. OBD, crocodile clips etc.) so it is probably something happened there, though I can't figure out how as it's impossible to fit improperly.

[steamship]

Originally Posted by HPsauce

However I do plug my "battery maintainer" solar panel in there too,

Second line in your original post and I missed that!

[HPsauce]

Just a little footnote on this. The OBD port is working fine but the "battery maintainer" solar panel has never been that effective plugged in that way, certainly not recently.
I wonder if there's something (apart from the fuse) in the positive circuit back to the battery that limits the current, I confess I haven't tried to find out what the route is and whether it's anything more than a fairly direct connection.

Anyway, having checked regularly and finding the battery is still slowly degrading I changed the setup and went for a direct connection to the battery using clamps on the terminals.
The solar panel sits on the back shelf, propped up and angled to face the sun around midday with the lead threaded through the ski hatch - it still closes OK.

It's not been like that for long but checking now I can see that battery is definitely getting "topped up" and is now stable at around 12.65V, it used to be significantly less. It's not in the best condition to be honest but given the comments in another thread (and my memories of doing it with Adrian's help) I really don't want to replace it this winter.

I'm now wondering if there's an easy way to permanently fix a short trickle charging cable (with a suitably safe disconnection point) to the battery cables; anyone done this to install a battery maintainer?

[HPsauce]

Originally Posted by HPsauce

I'm now wondering if there's an easy way to permanently fix a short trickle charging cable (with a suitably safe disconnection point) to the battery cables; anyone done this to install a battery maintainer?

I did notice the clamp on the big red positive cable seems to have an unused pillar with a screw thread, so I could fix positive to that. Anyone know what it's for?
Negative can presumably go to any convenient earth point or be strapped onto the negative cable - it seems to have enough exposed metal to do that.

[steamship]

Originally Posted by HPsauce

I'm now wondering if there's an easy way to permanently fix a short trickle charging cable (with a suitably safe disconnection point) to the battery cables; anyone done this to install a battery maintainer?

When I bought the CTEK charger when I had the S8, I got some additional accessories to go with it. One of them is the following from their site, a CTEK Stanadard Attachment Lead. It's basically a lead with their propriety connector on one end and eyelet connectors at the other. I just connected both directly to the battery.

https://www.smarterchargers.co.uk/pr...nt-lead-56-260

Halfords also sell another CTEK one, whichhttps://www.ebay.co.uk/itm/256618112843 is basically the same, but with a waterproof cover on the end:

https://www.halfords.com/motoring/ba...or-166622.html

You could probably get a set of male/female plugs and splice them into your solar panel and one of these CTEK cables (other brands may be available).

EDIT: Just came Deutsch connectors on eBay. £4 for a pair of 2-pin waterproof connectors, rated to 7.5A. After that you just need a couple of eyelets and a length of 2-core cable, and you can forget the CTEK cable:

https://www.ebay.co.uk/itm/256618112843