Fixing factory tach

[racerkilla]

So my factory tachs in both amx's did not work. I ended up buying a sun brand tach(the sweep is very close to the same) and used its new guts using the original amc face plate

I mocked up the new circuit board and two new screws into the old face plate to hold it. I took the original tach hand and cut just the white pointer off. Cut the new tachs orange pointer off and re glue the original on to the new tach base. The hole size was different.

new tach


old vs new pointer


new board on old face plate


old pointed glued to new base


When installing add 12v power so you can put the needle on the 0 rpm

Clean tach face done vs how yellowed the speedometer was. Used normal car wax and some elbow grease


both done

[vangremlin]

Very cool solution.  Thumbs up to you!

[Prafeston]

The Tach is still accurate? Cause I believe my tach is also non-function. Would love to fix that!

[racerkilla]

It's pretty close because the sweep is off some from new to old faceplate. 1000 off over 8000 rpm sweep. So couple hundred at 5k. Works good enough for me

[Prafeston]

While you had it apart could you see what was causing the old one to fail?

[racerkilla]

Never looked into the burnt one.. Was happy to remove it because years back my black amx just died, no spark and left me. New pickup, coil, control box no start. Tach burnt up and was grounding coil so I had cut the wire going to it and it started. Now I run all hei anyways and carry spare module

[amcfool1]

hi, there is a thread here about using a Ford F150 300cid tach, it sweeps to 6k, got one in my 84, works great! thanks, gz

[racerkilla]

Thats good to know..Problem is I need a tach for a v8 since that what is in all of my amx's. Maybe that style ford with v8. The sx4 I don't care how high its revving.. let it keep going

[vangremlin]

Thats good to know..Problem is I need a tach for a v8 since that what is in all of my amx's. Maybe that style ford with v8. The sx4 I don't care how high its revving.. let it keep going

The same Ford tach will work with a V8, there is an extra post on it the you run a ground wire to and you're good to go. Let me know if you need more info, I also have some of the Ford tachs for sale.