When driving today look down and my tach is at 4 and a half but engine is at idle. Key on engine off goes to 4 again.
Ideas?
Ideas?
I have attempted to peek inside the tach circuitry with very little success. I do have the tools and chart to calibrate them, but not info on what the circuitry actually is. I don't have any diagrams and no parts list that crosses over to commercially available parts. If anyone actually has a diagram of an 87-93 Fox body tach, I sure would like to have a copy.
I do have a copy of the older Fox body tach diagram from the early 80's 4 eye Mustangs
I already know that much, I have a spare instrument cluster from an 89 Mustang GT. I have done the tach calibration routine several times. I know how to get excellent accuracy +/- 35 RPM over a narrow RPM range It ends up being slot about ~200-300 RPM wide. You can choose where you want that slot in the tach's RPM range.The tach circuit board is actually easy to get to. You must remove the overlay and gauge as a whole. Then there are 3 nuts that hold the board to the gauge. Once that is done, you can easily spot the resistors that are the problem by the discoloration around them. The solder joints tend to crack from the years of getting hot. Its a simple fix. And if you need to replace the resistors, they are easily identifiable once you have the board off.
Test them to make sure...So these problems are unrelated but started at the same time? Assuming all grounds are good?