Why are the lights on my tachometer jumping around?
A needle that jumps around and shift lights that fire at random may look like a huge problem, but in fact they are usually caused by a simple issue that is easy to fix. First, let’s narrow down the symptoms. Too many times we get emails that just say the tach is “acting weird” or is “inaccurate”.
Why does my spa tachometer fire randomly at idle?
Since the spikes are random, they confuse the tach into bouncing up and down, usually reading higher than the actual RPM (but almost never by a constant factor). Shift lights will fire randomly, sometimes even at idle. SPA tachometers seem to be particularly sensitive to these spikes, but Auto Meter and Stack tachs seem to be much less affected.
Is it bad to move the needle on a tachometer?
In this case, the needle movement sometimes (but not always) might be acceptable at idle or even while free-revving the engine, but might be bad under load and/or at higher RPM.
Why do my Bosch tachometers have random spikes?
The first possibility is a “dirty” signal from the coil. The Bosch Blue coil in particular is notorious for having random secondary spikes after the plug fires. These additional little spikes are read by the tach and shift lights as another firing of that cylinder.
Why is my tach jumping at 5000 rpm?
I put my MSD box and my Auto Meter tach and speedo in and mine kinda does the same thing… when first started the needle jumps about 2000 rpms and then goes away when it warms up a bit. Also, at about 3000 rpm it will jump around 500-1000 rpms.
Where to find the tach signal on a tachometer?
Verify you are using a proper signal source. The most common locations for a tach signal are the negative terminal of the ignition coil or tachometer output terminal (HEI, Ignition Control Boxes or ECU). Verify 12V ACC, signal and ground connections (see above).
What should the tach read at 1500 rpm?
Now just adjust the potentometer until the tach reads 1500 RPM. or with your engine until it matches the working tach. feel free to check the calibration in multiple places, i.e. 300Hz = 4500 RPM and others just to make sure it is mostly linear.
A needle that jumps around and shift lights that fire at random may look like a huge problem, but in fact they are usually caused by a simple issue that is easy to fix. First, let’s narrow down the symptoms. Too many times we get emails that just say the tach is “acting weird” or is “inaccurate”.
I put my MSD box and my Auto Meter tach and speedo in and mine kinda does the same thing… when first started the needle jumps about 2000 rpms and then goes away when it warms up a bit. Also, at about 3000 rpm it will jump around 500-1000 rpms.
Why does the needle bounce on my tachometer?
So if the Tach is good, then the jumping or bounce is being caused from the distributor cap to the tachometer? More than likely what it is, it corrosion in the wiring behind the gauge. The gauge needs a good ground to work, if there is corrosion on it, or it’s a lousy ground, the needle will bounce.
What to do if your Tach is jumping?
Take off your distributer cap and pull the rotor off, then locate the connecter beside your distributor where the wires connect to the distributor. Disconnect the wires at the connection, using an ohm meter check the resistance of the wires coming out of the distributor, right this number down.