Replace Coil and Dash goes crazy

[gmhowe]

Noticed the white coil wire on my 85 had melted the insulation and sortof melted to the coil housing, so I replaced it. Started up the car and the MPH display is looking and running more like the TACH, my miles traveled are increasing by themselves and my instant MPG changes by itself, all while idling. the Tach still runs but seems low. any help

 

[Eagle85C4]

It is quite possible the tach filter has gone bad...,.bypass it and see if the symptoms are still there...if not replace the filter. By the way...they do not make it anymore but I have a schematic for it if you want it...

 

[gmhowe]

Is that the connector next to the BAT on the Distributor ??

 

[Eagle85C4]

The white wire goes down to the rear of the driver side head on the motor to a silver can that is attached to the head. From there it goes to the dash. you can remove the filter and use the wire on the other side of the filter to hook back into the distributor. Bypassing it. The problem with the filter is that the capacitors used are not heavy enough or rated high enough on the heat scale. After getting the heat from the head where it is attached it goes to ground which will give you problems. The filter is meant to keep "noise" from the distributor from affecting the dash. You can run without it but it is recommended that you keep it in place. It is possible to rebuild it as I did with mine. But I need the old one to build the new one in to maintain the look....

http://corvette1984.freewebtools.com/DIRECTORIES/REPAIRS/TachFilter/TachfilterDiagram.jpg

This is a pic of the filter...Thanks to Suzie and Christian

 

[gmhowe]

I kept playing with the 2 connectors on the Distributor, finally the whole dash went blank then came back and all is ok now, thanx for your help. Just another twilight zone episode ........