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ECU & Re: Pressure Transducer Failure


I have a couple of the stock pressure transducers that were
used in the MAC-05/07/10/11/12/14 ECU's. These were taken
out of ECU's that I upgraded with the 2.5 bar pressure

There are some Q-listers in Colorado who likely have extra
pressure transducers as well, where are you located?

You may want to verify the transducer is dead by removing
the ECU top and then use a voltmeter to check for the +5V
supply across pin 2 and pin 19 on the transducer. (Ignition
key should be on during this test)  The main ckt board has
the pin numbers stenciled on it. Pin 1 is the  transducer
output, it should be around 2.5-2.7V with the ignition key
on but with the engine off. (The exact voltage you see will
depend on what the altitude is at your location). 

There is a 5V regulator on the ECU main board that could be
dead. This should prevent the car from running at all

Pin 17 on the ECU should be the boost gauge output voltage
from the transducer.

BTW: The MAC-07 equipped 1985 5000T KH turbo engines can
use the MAC11 ECU, you need to remove the Hall Sensor
ground return wire connected at pin 4 at the ECU harness
connector and connect it to pin 23 in order to use the
MAC11 in these cars. The car won't start unless you make
this change.  BTDT, this may also apply to the MAC-05
equipped cars. The MAC-07 ECU's do not appear to have a
stand alone EPROM but I believe they have the code imbedded
in the uP ROM.

Scott M.
89 200TQ

> From: audial@aol.comLaw Guest Account
> To: quattro@coimbra.ans.net
> Subject: Wanted: '85 5KT (non-Q, auto) ECU & Re: PT
> Date: Thursday, November 13, 1997 8:49 AM
> The pressure transducer on my dad's '85 Turbo has failed.
 It currently
> reads 0.0 at the dash all the time, and we checked the
wiring as well as
> the codes.  
> Does anybody have lying around one of these ECUs (or just
the 2.0BAR
> transducer) that they'd be willing to sell?  This
computer is not a MAC-11,
> I think it's a MAC-05, but the pressure transducer looks
to be identical.  If I
> can get a replacement I'll be happy to perform an autopsy
on the existing
> sensor to try and isolate the cause of death.  I'm fairly
sure it wasn't
> boost overpressure on his car, though.  It was
intermittent for some time
> before it finally crapped out completly.