"New" Audi 100 turbo Avant

[Phil Payne]

Since I bent the old one, I looked around for another.

GBP350 - around $500 - bought me an Audi 100 turbo Avant (FWD) with a mere 269k miles on it.
Upholstery and body pretty close to perfect (pale grey velour and silver metallic).  New tyres
all round - full size spare.  Drilled front rotors and Paget road pads.  Load securing eyes in
the luggage compartment.

Failed MoT test on "insufficient handbrake efficiency and a bulging flexible brake line" -
fixed both and it's legal.  Sounds like a Swiss watch - not a rattle or a bang on the car,
except for a very occasional light clatter from the throw-out bearing.

WoT switch was knackered, Michelin man hose held together with tape.  Hydraulic pump leaked
1ml of G 002 000 per mile, so rebuilt that with new seals and fixed it.  Fitted the ECU and
wastegate spring out of the old bus - now pulls 1.8 bar.  Replaced a quite decent Philips
stereo with the Blaupunkt Travelpilot out of the old bus, so I now have satellite navigation.
It already had the ISO connector blocks, but I had to add switched power, speedometer and
reversing light connections, as well as mount the satellite antenna on the front of the
dashboard.  You have to gut the interior to do this, so I fitted a "Check Engine" light and a
pushbutton to trigger the codes.  Did the bouncy needle repair and swapped some dahsboard
bulbs while I was in there.

I fitted a diagnostic system - a "check engine" light (even lighting up the right symbol on
the auxiliary dashboard) and a push-button to control it.

Minutes into the first drive - a "check engine" light. Quite amusing - in the MB and RR
ur-quattro Owner's Handbook it basically tells you to panic if you see this light - on the
Type 44s there's no light fitted, even though they sometimes use the same ECUs.

Anyway - got 2312: coolant temperature sender. Checked it out - seemed fine. Pulled the ECU
and checked the harness - fine. Swapped in the old ECU - same problem.

This is a goodie. The (undocumented - not on the wiring diagram) fuse in the common chassis
ground from the radiator fan had failed - an almost invisible crack down the middle. Thus the
fan wasn't working and the radiator was overheating. But the electronic thermoswitch circuit
that runs the dashboard gauge was under-reporting - so the dashboard gauge was reporting
normalish temperatures even though the engine coolant was at around 135c. The ECU was calling
the temperature sender for low resistance via code 2312; it _WAS_ low, but not because the
sender was faulty - the engine was too hot.

This is a potential cause of 2312 on MB, RR, 1B, MC, ADU and a number of other engines.

--
  Phil Payne
  http://www.isham-research.com/quattro
  +44 7785 302 803
  +49 173 6242039