[jay_pearce]

I have a 1966 a-code with an original rally pac tach and clock. Last instrument I need to get working properly is the tach. for what ever reason, it is reading VERY high. at idle it starts at 4500-5000rpm when its running at about 600-700 in reality. the needle goes up if you rev it up, so its receiving a signal. I was wondering if there was anybody that know how to trouble shoot the install of one of these. Lots of info on the aftermarket ones, but they operate on a totally different principle.

 

[rex1965]

What type of ignition do you have, the original tachs were designed for points and condensor? Good Luck.

 

[jay_pearce]

The stock ignition...

 

[rex1965]

I'm an electronic tech, also, so either some components have gone bad over the years, like either some capacitors or maybe potentiometer (kind of like a volume control) is used to calibrate the tach, this calibration must be done usually with a tach of known calibration, like a Sun Machine or equivalent or a device that produce a certain number of pulses per minute (like for 5000 rpm, V8, is 20,000 pulses per minute). You might see if you can find someone who repairs them. Good Luck.

 

[jay_pearce]

Thanks. I will see what i can find. Since it is the original that came with the car, it is likely worth it... They seem to be a fairly rare option.