Last night while coming home from a short in state trip in the rain, the
speedo on my '89 GT started jumping up and down about 20 mph, then just quit
working and dropped to zero. (all other gauges working fine, but anything on
the digital system related to speedo signal stopped also) I don't think that
it is anything pod related, but it appeared to me to have lost an electrical
connection somewhere, most probably at the sensor?? I have the manuals on
CD, but am having problems finding where in the manuals the info on the
speedo sensor/signal sender and where it's located. I was thinking that it
was somewhere on top of the transaxle, but I'm not sure. Any help with
either the speedo problem, or manual location of the info I seek would be
greatly appreciated. TIA,
'89 928 GT
Speedo/odo sensor is a reed switch mounted in the rear cover of the differential, operated by magnets on a ring mounted to the differential.
The most common problem is a bad connection at the connector in the forward right corner of the spare tire well, although a bad connection inside the pod can also cause this.
The speedometer signal doesn't go thru the Central Electric Plugs on your car.
A brown/red wire runs from the rear to terminal 14 on the digital dash connector. (Page 97-289, Zone J30 to Zone D25) A brown/red wire also runs to terminal 11 on the cruise control connector.
(Page 97-301, Zone B87 to Zone B88)
This shows the analog instrument cluster (up until 1989 model) speed signal circuit.