I have an '87 Pulsar (E16i SOHC) Engine with 155,000 miles on it. For the last couple of days the tachometer has been fluctuating inconsistently with the true RPM of the engine. For example, I'll be driving at 65 MPH with the tach reading around 3000 RPM (normal) and then all of a sudden it will drop to a few hundred RPM or even zero for a few seconds and then it will return to normal. Or sometimes, when the car is first started it will read zero and then it will be normal. The engine runs smooth and starts just fine so the problem seems to be just with the tach. The other gauges are working fine. Does anybody know where the tach gets its signal from or the location of its connector under the hood? If someone knows of an online source or could post the schematic for the tach circuit that would be great too. Thanks.
Erratic Tachometer on '87 Pulsar
Feb 09, 2008
3 Replies
Next time it happens, whack the dash hard above the tach and see if it fixes it. If it does, it's likely the tach unit.
There's a voltage regulator on the back of the instrument cluster too. I forget if it will cause erratic operation or if the gauges just die when it goes bad.
I have a similar problem with my '91 Pathfinder and it also affects my speedometer, but it is very occasional and whacking the dash usually produces a useful reading. I have checked the speedo on measured miles, and it reads fairly consistently 5% low at highway speeds.
I tried hitting the dash as you suggested but no change. If the instrument cluster regulator that you're referring to fails, it affects not only the tach, but the fuel, and temp gauges as well. In my case, all the other gauges are working fine. Also, when the regulator fail, it's usually done for and not intermittant. Hopefully, this will help someone with a similar problem. T.C.
Join the Discussion
Have something to add? Share your thoughts — no account required.
Didn't find your answer?
Ask the community — no account required