Tach Issue
Thread Starter
Instructor
Joined: Dec 2005
Posts: 147
Likes: 0
From: San Antonio Texas
Tach Issue
I have run into a issue with my tach on my 79. It has a msd ignition installed and I have connected the tach wire to the tach output on the msd but the rpm's dont appear to be right. when the car starts it reads very low like 500 RPM instead of 5000. I have replaced the circuit board for the tach and still no luck. have any of you ran into this before. Also the tach worked previously in this set up but after I got it back from paint it had died.
Le Mans Master
Joined: Jan 2007
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From: Omaha NE
2025 c3 ('74-'82) of the Year Finalist - Unmodified
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Must be hard to keep it in place at red lights.......
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Are you running a tach filter? My Crane box, similar to a MSD box says to not run a tach filter if you run off the tach lead of the box. I called Crane on this and they confirmed it. Check with MSD and see if the tach filter is needed, if you are running one.
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Thread Starter
Instructor
Joined: Dec 2005
Posts: 147
Likes: 0
From: San Antonio Texas
there is no tach filter. I am stumped in troubleshooting this as it seems to be a prety bassic set up. I only can be a couple of things. the tach and circuit board, wireing or msd box. How do I trouble shoot each of these?
Racer
Joined: Jul 2005
Posts: 499
Likes: 1
From: Winnipeg Manitoba
take an AC power adapter that puts out 6-9VDC.
Take it apart and remove the filter capacitor.
Put it back together and hook it up to your tach.
It should read 1800 RPM when you plug it in.
P.S. Please don't electrocute yourself!
(I always have to add that when I suggest someone take apart electronics)
Last edited by Kilroy1024; Feb 4, 2007 at 06:45 PM.
Racer
Joined: Jul 2005
Posts: 499
Likes: 1
From: Winnipeg Manitoba