Unruly Tach

[dgently]

I have been puzzled by my unruly tach. I noted early on that 3000 rpm equated roughly to 60mph.

These days, as often as not, I'm reading 4200-4500 rpm @ 60mph. From a cold start, it will be back reading 3000 at 60.

I'm pretty sure the speedo is reading consistently - but I've come to think that my tach reads higher when the engine is hot.

Any theories?

[Expat+2]

Could it be voltage related? After a cold start there will be a heavy draw on the alternator.

I had my tach redone at Speedy Cables for a very reasonable price.