My tach rises to 1500 with key off. when starting it returns to 0 then reads 15-1800. it stays that far off or more as rpm increases. and pegs out when true rpm is about 5000. I have read the tach repair thread and checked my resistance on pins 4 and 10 . It is on the money at 196k ohm. I just recently replaced the circuit board on the back with a new one. The old one had several broken spots but the tach worked fine.All of the contacts in the pin plugs are making good and correct contact . and the part number is the same as the original. The tach had never been out of the cluster before i checked the resistor as stated in the repair thread. Also the temp and oil pressure gauges stay where they were when the key was shut off they don't go to 0.

 

what we need is for one of the tech gurus to do a write up on this all too common problem. there is one for the later style(are the electronics the same?)but so far no love for our early tachs