Aftermarket Gauge Question
Thread Starter
Burning Brakes
Joined: Mar 2005
Posts: 861
Likes: 0
From: WNY
Aftermarket Gauge Question
I have an aftermarket tach since I switched from points to HEI. The gauge keeps acting up thought - it will jump around a bit, and give all sorts of crazy readings (for example it thinks Im idling at 3400rpms sometimes). Is it just the gauge being quirky or do you think it could be something in the wiring. Most of the time it seems to read fine, just every once in a while it will jump up a couple of thousand RPMs.
Drifting
Joined: Jan 2002
Posts: 1,645
Likes: 11
From: Schaumburg IL
On a 77 with an HEI distributor I assume you hooked the tach wire for the gauge to the tach terminal on the cap. If it is jumping all over check the internal connector and check for corrosion. If this is all ok and the engine seems to run ok, does not cut out and timing stays stable with a light, maybe the gauge is funky. Otherwise the tach circuit inside the dist probably has a problem.
Thread Starter
Burning Brakes
Joined: Mar 2005
Posts: 861
Likes: 0
From: WNY
Its a 74 (I really need to change my username...) and it is a fresh motor with a brand new mallory HEI unit.. Im just wondering what else could cause it. Kind of sucks never knowing if my tach is accurate or not.
It seems to hold fine on a light, never had any issues when timing it.
It seems to hold fine on a light, never had any issues when timing it.
Drifting
Joined: Jan 2002
Posts: 1,645
Likes: 11
From: Schaumburg IL
Then we probably assume the HEI is good as it is new. I would look at grounds for both the HEI which I believe is internal and grounds for the tach. Take an ohm meter on rx1 scale and check the ground terminal on the connector (the wiring diagram for the HEI should show this) to a engine ground. There should be zero ohms. Same for the ground at the tach. Also, with the engine running check for +12vdc at the HEI connector and at the tach.
If all ok, go to an auto store and pick up a 20 buck tach and try it, maybe your unit is bad.
If all ok, go to an auto store and pick up a 20 buck tach and try it, maybe your unit is bad.
