Resurrection of my CQ20V

[John.]

I've never had a speedo issue but if the sensor on the box is of the inductive pulse type (2 wires going to sensor), then it (the sensor) will produce an AC voltage when the wheels are turning. The voltage can be checked at the sensor itself and at the loom.
If it's a hall effect sensor it can be checked with an LED test light.

F*** pulling the box apart just yet!

[Bowie69]

Very useful post here:

https://forums.quattroworld.com/s4s6/msgs/168463.phtml

Will check continuity again then swap the speed sensor ring from my old box- note it is a not a reluctor ring as I suggested above, apparently a reed switch + magnets! Eight pulses per revolution.

Live and learn

[Bowie69]

I've never had a speedo issue but if the sensor on the box is of the inductive pulse type (2 wires going to sensor), then it (the sensor) will produce an AC voltage when the wheels are turning. The voltage can be checked at the sensor itself and at the loom.
If it's a hall effect sensor it can be checked with an LED test light.

F*** pulling the box apart just yet!

Ah thanks John, see my latest reply which negates what I said before (didn't see your post before replying again)

It's magnetic, not inductive, but that does mean I can test with led as you rightly say, so certainly a thing to try

You can swap the ring out by just removing one driveshaft and the diff cover, so not too bad

[John.]

You can swap the ring out by just removing one driveshaft and the diff cover, so not too bad

[Bowie69]

No prizes, but feel free to have a guess as to what this is:
20210523_160712.jpg It has helped me enormously today!

[Bowie69]

Awe, despite 20 views, no takers....

That is the top swivel pin bearing from a range rover, with a large bolt tacked into it and the magnetic speedo trigger ring from my old gearbox.

The drill I reckon you worked out

I unplugged the gearbox loom from my car and plugged a spare speedo sender into the loom, then ran the trigger ring in the drill up against the sender and the speedo worked!

This is excellent news as it means the speedo head and all the wiring from dash to gearbox is fine, and it means the problem is categorically to do with the trigger ring inside the gearbox.

Sounds like a pain , but I reckon it will consume less time than trying to find an electrical problem somewhere in the nicely wrapped factory loom.

So when it isn't pouring with rain I'll get in there and find out what's happened. I did check, and reckon it is possible to put the trigger in the wrong way round -at least I know now which way it should be from my old gearbox.

Incidentally, my old box is showing quite a bit of silver glitter in the oil, and the trigger ring had quite a good bit of paste stuck to it! Definitely needed to be swapped out...

[Bowie69]

Sooooooo....... few weeks on, and I still haven't dived into the gearbox yet, so no speedo fix to report on, soon honest

Went shopping Monday evening, ABS and charge light came on as I pulled into the car park

...then immediately extinguished....

Visual check shows everything OK, voltmeter check shows things nearing 11.5V, at the dash, which is 'nicht gut'.

Back home, swapped out an unknown spare regulator with no change, though the old one could be dead of course...

Brand new Bosch part ordered yesterday from these guys, that I find very prompt on Ebay: https://www.ebay.co.uk/usr/carpartsinmotion

Paid extra for next day service and arrived about 11am this morning via Fedex (whom I am having more and more respect for, a courier that does what it says!). 15 minutes of fiddling in the front of the car and have it fitted, and car charging again -fantastic, as otherwise the cheapest whole alternator I could find was near £200.

For those with interest, on a 7A coupe without air con, or a 3B S2 without air con (both 90A alternators) the Bosch part number is 1987237059, which references to 034903803 Audi/VW part number

Also fits loads of other Audis, as can be seen here: http://www.oemepc.com/tvn_result/search/tvn/034903803 , though I found much better results by looking via the Bosch part number once I had the cross reference (Autodoc can be very useful for this, even if they are useless for actual parts delivery.)

[John.]

For those with interest.....

Good reference info, cheers.

[Bowie69]

Good reference info, cheers.

Yeah, when I spend time finding stuff out, I prefer to post it, as could help others, and include keywords like 7a, 3b etc so the search engines find it better

[John.]

Yeah, when I spend time finding stuff out, I prefer to post it, as could help others, and include keywords like 7a, 3b etc so the search engines find it better

I make a point of commenting, as well as thanking you for useful info it means I can check my posts if I can't find stuff via search options !

My CQ is still taking a rest in the garage but when it's moving again your info will come in handy I'm sure

[Bowie69]

I make a point of commenting, as well as thanking you for useful info it means I can check my posts if I can't find stuff via search options !

Yeah, had noticed, much appreciated, means I don't feel like I am speaking into a black hole

[John.]

Yeah, had noticed, much appreciated, means I don't feel like I am speaking into a black hole

Folks are listening

[psiconauta911]

Sorry mate not much of a writer but an avid reader!
Here every day and read every news!

[Bowie69]

No need to apologise one bit

[steve briance]

Im watching and soaking it all up as well

What does your volt meter show on the dial now? Mine only goes just above 13v maybe nudging 13.5 as far as you can say from the scale...