The speedo in my car right now, reads about 4-5 over at 70 mph as well.

Forgot to mention, the work I had done, 12 capacitors was $200. Hamps does not show Mazda as a brand they work on, but call them and talk over your issues, they are super nice.

 

Did they tell you what they had to do to repair it or keep it a "Trade Secret"

 

They had to replace the circuit board for the tach. Instead of re-soldering it like a lot of members here do, they replaced the whole board.

 

So when the weather finally broke in NJ a few weeks back, I installed my Hamps cluster. Much to my dismay the tach didn't even flicker. Gave Hamp a call and he assured me it was tested with a signal generator.

Fast forward to today, I pulled out the cluster and started looking around at the plugs, figuring I was going to have to do the jumper mod. Low and behold on the tach signal wire is a bullet connector and some electrical tape. Someone has already been in here. I pull the pin out, cut the tape on the harness back a few inches and solder it all back together. Plug and it and nothing. F'this thing. I cut the pin off and jump it over to the screw terminal on the back of the tach. Success. Until..................

I am driving the car for 10-15 mins, tach is working great. Then on light or no throttle the needle starts to drop and flutter. So who knows at this point. Gonna leave it for now and revisit if it stops working completely. Have other things to address at this point.