Hello everyone, thanks for your time to reading this. So, I have a 1989 XJS 3.6 and my speedo has never worked. Nor does the console computer thing work (it comes on but doesn't record mileage/fuel consumption etc). So, I took out the whole dash and cleaned all the connectors (even though they didn't really need it because everything looked in first class condition). Knowing that brand new DAC4591 (the little black box thing that sits in the boot, hidden on the left hand side) i.e. 'Interface Speed Transducer' for pre-facelift models no-longer exist, an auto electrician first tried a new Speed Transducer for the facelift model, by swapping over the connectors. That didn't work. So, I bought a second-hand pre-facelift DAC4591 (exactly the same one as it was replacing). And it still doesn't work!! I'm no good with electrics so will get the auto electrician to test the part in 10-days time when he returns from holiday (I bought it from a reputable dealer and just assumed they'd tested it). Maybe I misheard my auto electricain a couple of weeks ago but I'm sure he told that power was getting to the wires that lead to the Speed Transducer, so it must be the old Speed Transducer that doesn't work. So, it seems that the curly wurly wires that come out from the axle area are working fine.

Based on all the above, am I missing something obvious here? Or do you have any suggestions as to how I can get the speedo working once and for all?

 

It sounds like you are not getting the signal from the speed sensor. It's located in the differential cover just above the fill plug held in by 2 small bolts. Inspect the wires and make sure they are not torn off. Then remove the bolts and slide out the sensor and inspect it keeping note of the white shims. Sometimes it needs cleaned.

 

do you still have the DAC 4591 interface unit?