Tach adjustment — revs too high

[Acollin]

1966 Series V — mostly stock

If not for a post from Tom H, ( Thanks Tom) I would not have been able to figure this out. His pictures informed my action and I was able experiment with the procedure on an old tach on the shelf so I knew what I needed to do for an adjustment.

I was able to accurately adjust the engine speed on my tach at idle without removing it from the dash.
Once I saw the “pentxzxzxzxzx” whatever pictured — where it sat in the gauge and what it looked like, I considered drilling a hole in the back of the gauge with the gauge in place. But—I found that if I removed the light bulb,I could reach in the bulb hole and turn the dial with my finger tip. I attached my old Sears rev meter to the coil and with the car running and me moving from drivers floor to engine bay to check the meter and compare it to the tach, I was in about 15 minutes able to synchronize my old tool to the tach.

I have not seen this shortcut posted. If the trick is public, please forgive me for jumping the line!!!

I hope this helps someone.
Be well all
Andrew
Sandy Oregon

 

[Alpine 1789]

Good idea! It never occurred to me to try adjusting it through the bulb hole. I drilled the hole.

 

[Tom H]

First, please do not ever drill a hole in the case without disassembling the tach. Just one or two chips of steel from drilling will get attracted to magnet inside that is part of the sensitive meter movement will very likely result in a very sticky tach.

I am surprised that you could rotate that adjustable resistor with just a finger, but I tried it myself on a couple tachs and found I could move a couple of them fairly easily. Good idea, I have not seen such a suggestion before.

Tom