Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
Welcome, I'm Chris (aka Moose), my normal schedule online is around lunch and after dinner past midnight.
Are you sure the tach in this new cluster works?
Do you have a analog multimeter to see if the white wire is rapidly pulsing 5 volts while running?
A scope or analog meter is needed to check this wires rapid pulsing power on/off.
A digital meter nor test light will work and low voltage can cause no or low signal.
Is it analog or digital?
A DVOM will not be able to monitor this circuit.
You will get a reading but it is not a usable reading to confirm accurate signal is being sent and received. The reading you get on the DVOM will not assist us in diagnosing this issue.
Prior to completing the mandatory rating at the top of your screen. Let me know if I have not yet provided you with ~5 STAR EXCELLENT~service. Reply and let me know in more detail what you need to be pleased with my help.
If you replaced the tach wire, verified the cluster works, and still no tach. That means the coil is to blame.
I have nothing more to offer on this concern. I will remove my self from this post by opting out so another can help.
Good morning, I've been looking over your question and what I gather is you do have tach signal at the coil but not at the white wire that goes into the cluster.
There is a connector between the coil and the wire at the cluster ( C203) in the diagram below. If it's unplugged or a bad connection this could be the issue.
With your volt meter check for continuity on that white wire from the cluster plug to the coil. (with coil unplugged) there should be les than 1 ohm of resistance. Let me know what you find and we can work further if needed.
I may of misunderstood. So the aftermarket tach does work at both the coil and the white wire at the instrument cluster connector?
In the facotry unit the tach and other gauges are powered by the gauge fuse. There's also a solid state computer module in the cluster that take take input and speedo input.
If the aftermarket tach works at the connector to the cluster it's most likely that stock cluster is bad.