Factory Tach Install

[Gennoy]

Hey All,

I rebuilt my gauge cluster installing a factory tach. I put the gauge cluster back into the truck and plugged in the tach to my HEI and tried to start my truck. Unfortunately I get no spark with the factory tach plugged in. Once I unplug the factory tach from the HEI the truck fires up just fine. I plugged in an existing Sunpro tach I had into the HEI and had no problems. So it seems the problem is with the new factory tach.

The rest of my gauges all work fine with the exception of the "Battery" gauge where the needle just sits in the center. I know my truck is charging correctly because I get ~14 volts at the battery when the truck is on. But it seems the needle doesn't move. Is that right?

Unfortunately I am not the one who took my truck apart (I bought it in pieces). So I am slowly trying to learn how to put it back together. The only things running to the cluster are the gauge harness plug, the oil pressure line and the tach harness. Is there something that I am missing? Or is it just a bad tach?

Thanks in advance for all the help.