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BJ8 Tach

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AN6-TX

AN6-TX

Jedi Hopeful
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Long story short, I have a tach I need to swap out and have a (used) replacement available. I do not - however - know the condition of the replacement. What's the best way to test it out of the car? My BJ8 is negative ground.
 
Does your spare tach say neg ground on the dial face ? If so switch it out it takes ten mins to remove it .
 
Healey/Smiths electronic tachs are essentially pulse counters with a small 'motor' to turn the indicator needle. You'd need a pulse generator to test one; something like this (most electronics hobbyists would likely have something similar):


AFAIK, all Healeys were positive gnd. from the factory; your current one would have been modified at some point.
 
no need to buy a pulse generator, when you already have one on the car. just connect it up
 
OP says his car is neg. gnd. but his potential replacement tach is pos. gnd. (see: previous posts). IIRC electronic tachs require some internal modification; e.g. some components, like electrolytic capacitors--generally, the cheapest--are polarity sensitive.
 
Correct - my hope was to be able to determine whether the tach currently works. If it does, I have someone locally that can modify it for negative earth; if it doesn't work, I will have it sent out, rebuilt and converted.

Admittedly, I am somewhat surprised that new tachs appear to be like hens teeth...
 
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