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> tach does not register over 2200 RPM but revs over 2200
TonyA
post Mar 19 2026, 06:49 PM
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My tach will not register over 2200 RPM even though it sounds like it revs way higher then 2200 the green wire is connected to the coil all grounds seem ok. Not sure what the problem is. Any suggestions.
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dtmehall
post Mar 19 2026, 06:53 PM
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do you have access to another tach?
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mgphoto
post Mar 20 2026, 02:12 AM
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QUOTE(TonyA @ Mar 19 2026, 04:49 PM) *

My tach will not register over 2200 RPM even though it sounds like it revs way higher then 2200 the green wire is connected to the coil all grounds seem ok. Not sure what the problem is. Any suggestions.



You should be able to borrow a tech from your local auto parts, that should confirm what your revs should be. There may be a problem with a circuit in the tech.
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rfinegan
post Mar 20 2026, 02:30 AM
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Bouncing needle and not responding to rev is very typical of a failing tach. Im told the capacitors break down and fail internaly. Are you running a points distibutor?
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brant
post Mar 20 2026, 10:21 AM
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Also failing points will cause plenty of tach problems...

but not sure what your ignition is.
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porschetub
post Mar 20 2026, 12:28 PM
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QUOTE(dtmehall @ Mar 20 2026, 01:53 PM) *

do you have access to another tach?

yes that would be a good start ,issue is they are very old with components that are the same ,the 73 911 one in my car went a bit haywire and sent it to guy and he got it stabilized , he said it tests fine ,my replay was "for how long ' his reply was no promises there so I got him to fit the new Ashlock tech driverboard I had sent him ,got back a tach that was absolutely spot on ...end of the day will never have to mess with it anymore, cost me $125NZD for the work and around $35USD plus shipping to import the driverboard .
Cheers .
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porschetub
post Mar 20 2026, 04:37 PM
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QUOTE(porschetub @ Mar 21 2026, 07:28 AM) *

QUOTE(dtmehall @ Mar 20 2026, 01:53 PM) *

do you have access to another tach?

yes that would be a good start ,issue is they are very old with components that are the same ,the 73 911 one in my car went a bit haywire and sent it to guy and he got it stabilized , he said it tests fine ,my replay was "for how long ' his reply was no promises there so I got him to fit the new Ashlock tech driverboard I had sent him ,got back a tach that was absolutely spot on ...end of the day will never have to mess with it anymore, cost me $125NZD for the work and around $35USD plus shipping to import the driverboard .
Cheers .

found a pic of installed board ,any instrument shop can provide this conversion if they can test a tach ,cheers.

Attached Image
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