Weird start/non-start problem - help needed

[moltuae]

For a slightly more serious suggestion I just thought of, how about an RF remote switch like this?:
https://www.amazon.co.uk/Channel-Wir...dp/B06Y586ZWP/

I've used dozens of these RF remotes for various projects. They work pretty well. And no need to find a place for the switch with one of these, just attach it to your keyring or leave it in a convenient cubbyhole.

[HPsauce]

Originally Posted by MikkiJayne

Sounds like... F125!

This is the same problem Neil had when the neutral lockout terminal fell off inside the switch

Attached is a photo of the inside of my old F125 which I decided to look at after thinking about your comment MJ.
I'm guessing that the top 4 contacts are 2 separate circuits for P/N and R and the lower 5 contacts signal what gear has been selected.
Not sure how Tiptronic works, when the lever is moved across in drive does the F125 move or not?

From the shape of the metal arcs it looks like the top one is for Park and Neutral with the second completing the circuit and the third/fourth for Reverse.
So, hopefully if there's damaged contact on the P/N circuit (it is currently working in P so not broken off) it may not affect other functions. Fingers crossed.

I also noticed that the Reverse contact points on the embedded metal strips are discoloured, especially the small one. Awful design!
From what I know of the wiring that's probably taking all the current to the reversing lights when they are on, so is almost certainly the most heavily loaded area for a significant time.
The P/N contacts are only briefly operating a relay during starting (NOT the starter solenoid!) and the set of 5 are probably just small electronic signals.

[HPsauce]

Originally Posted by HPsauce

I've already made up a wire, using 6.3mm tags as MJ suggested. I'll try it another day though, once I've worked out EXACTLY which holes to bridge - don't want to blow a fuse somewhere!

This morning being sunny, I decided to look at the J207 a bit closer. Attached is a photo of the socket with the relay removed.

It's interesting in that although the two thick red/black wires are actually the starter circuit (pins 30 and 87) on the relay they use what appear to be thinner steel contacts.
The wire from the F125 switch is thin and goes to the big lower copper socket, pin 85.

The top big socket (pin 30) is just fed by a short loop of wire from pin 86.
This is actually shown in the wiring diagram MJ posted earlier, I just hadn't registered that...…
For reference the pin correlation between the wiring diagram and relay numbers is as follows:
2=30
4=86
6=85
8=87
Anyway, my assumption now is that to bypass this relay I need to put my wire in the steel contacts (30 and 87 = 2 and 8), connecting the two thick red/black wires.

[MikkiJayne]

This is the factory piece fitted to manual versions



No idea what the part number is though, hence why I made one instead.

[moltuae]

Originally Posted by HPsauce

Anyway, my assumption now is that to bypass this relay I need to put my wire in the steel contacts (30 and 87 = 2 and 8), connecting the two thick red/black wires.

You could confirm by sticking a voltmeter (or lamp/LED) across what you believe to be the relay coil terminals, which might also be a good way to check what's coming from the F125 and whether there's any visible intermittency.

[HPsauce]

Originally Posted by MikkiJayne

This is the factory piece fitted to manual versions.

Yes I've seen links like that before.
That isn't a photo of the J207 socket though, is it...……

Originally Posted by moltuae

You could confirm by sticking a voltmeter (or lamp/LED) across what you believe to be the relay coil terminals, which might also be a good way to check what's coming from the F125 and whether there's any visible intermittency.

Yes I plan to do that before shorting it out. I've got help coming at 1:30pm today.

[MikkiJayne]

J207, but not in a D2

[HPsauce]

OK, initial job done with help from my retired garage-owner friend.
We tested when the short-circuited terminals there were "live" and it was only when the ignition key is in the start position, so no possibility of battery drain etc.

And we of course were able to start the car in any gear lever position, though it's extremely unlikely I'd do that by accident given the interlocks between gear lever movement, key removal and brake pedal. I've left the relay bypass wire in for now. Though everything is all "hanging out" in the footwell.

We did this just as the weather turned again, so at some later date I'll go back and test more thoroughly, checking continuity through the F125 as the gear lever is moved. Also, when Franks relay arrives I'll do some testing on both mine and his to see if it's possibly a relay issue.
(Orange drains and putting everything back tidily will all be done at the same time)

Incidentally I think the R circuit in the F125 is OK as that also powers my reversing camera and that does come on.
And the rear parking sensors also fire up, they probably get triggered by the same circuit though I don't know for sure.

Thanks everyone for your help. This place is invaluable.

[HPsauce]

Originally Posted by MikkiJayne

J207, but not in a D2

Indeed; trying to find the part number I stumbled across that picture on Audiworld in an S4/S6 thread: https://www.audiworld.com/forums/aud...rcuit-2860035/
And in there the relay used is indeed the same 204 type.

[HPsauce]

Originally Posted by HPsauce

Whenever my aircon drains have blocked I get the water dumping noisily out of the tray on cornering. Ever since I trimmed the orange drain tube tips that's not happened.

BUT I did find the scuttle full a few weeks ago, so I reckon it's probably overflow from that and has just stayed there since.

Confirmed. I took out the (easier) passenger side trim today and all was indeed fine, no water.
Some non-blocking debris in the (trimmed) orange drain so I blew that out and refitted it. Some day I'll look at the drivers side.