HELP! Using a SUN ST-810 4 cyl. Tach on V8 engine

[68bronco1x]

I have a really nice Sun Super Tach 8000 RPM blue line ST810 4 cyl. tachometer that I would like to use on my 68 bronco V8 302 engine. The tach has the solid state electronics in the meter itself unlike the earlier Sun tachs which had a separate sender box. I understand that the tach will work on V8's but will read 2X the RPM on the meter scale. Is there anyone that has technical knowledge of how to get this tach to work on 8 cyl. and read properly on the scale. If anyone out there has an ST-802 8 cyl. tach that they have ever taken apart the board could be compared. I would think that it would only be a component change. I know there is some tach adapters on the market but I am on a limited budget. Any technical help would be greatly appreciated.

 

[Broncobowsher]

I couldn't find that exact model. But it looks like ones I have dealt with in the past.
Take the back cover off. There is either a switch that has setting of 4-6-8 that just needs to be turned. Or there are a couple loops of wire that have been cut that need to be spliced back together.

 

[68bronco1x]

No, this one does not have any switches or loops of wire. You are probably thinking of the ones that were the later versions that had the plastic covers. You can go to the links for a diagram and picture of the Tachometer.

[img=http://s20.postimage.org/bs2d9ktzt/Sun_Tach_Diagram.jpg] [img=http://s20.postimage.org/skxmlqw2h/ST_810.jpg]

 

[Quick & Dirty]

I have a Sun Super Tach II, which has the switch. Decode the colors for the ohm readings.

 

[68bronco1x]

re: tach

Thanks for the picture of the Sun Super Tach II. This may help to some extent.
The Tach that I have is the earlier version. It is a Sun Super Tach RPM. This tach has a metal meter case and circuit board is in the meter. I need information on that model.

Thanks Again

 

[Rustytruck]

http://www.ashlocktech.com/TACH-ADAPT.html