REV 1 rev counter (mechanical)

from memory there is a signal from the ecu which drives the tacho. i think it also appears in the diagnostic plug.
if the tacho is working a bit (just not responding very much), then there used to be a post about replacing the capacitors on the tacho board. i have recently done this with stuka (even though the link appears to be broken now). Let me know if you need more info...(i have a spare panel at home to look at!)
chris

hi, am home now, so have access to wiring diagrams and the spare instrument cluster! (a later model electronic one, but still useful).
the ECU lead is IGN which connects (eventually) to one of the three screws/electrical connections which hold the tacho into the cluster (or combination meter, as the electrical diagram knows it). according to the wiring diagram (p 164 of 1991 wiring) this is on pin 3 of connector C11 (A) which on my panel is behind the speedo (middle plug). looking from the back of the panel the pin is third from the left - you should be able to trace the copper land to pin identified as IG- (if you have removed the panel and its back!). It should be a black wire into the plug.
i don't see any reason why a shift light and tacho shouldn't both work as i have seen this working elsewhere - but maybe the shift light installer cut the IGN wire to install it??? :-(
IG- does also appear on the check connector (pin 18, page 56 wiring), but it seems the signal is getting up the front as the shift light is working.
hope this helps.... Chris
 

no probs... hope you get it sorted.
 
the wiring diagrams can be found at:
 
http://www.mr2.com/files/mr2/techinfo/
 
91mr2_ewd.pdf is the 91 version. good searchable PDF with colour. worth every penny of the download cost :-)
 
look forward to hearing how you go.
Chris