Usually my tach works fine, it goes up and down depending on the position of the loud pedal...

but once in awhile it sticks at ~2500 rpm or so no matter if the revs are high or low, or in between.

I swapped in an identical NOS gauge and it acted the same way. I have cleaned up the tach wire contacts in the relay board where the harness connects to it and the condition continues...if it was just dead (0 rpm), I would guess maybe an open circuit, but that it hangs has got me stumped.

Your ideas my most esteemed 914Club brothuhs and sistahs...?

I had a tach that did this but it was specific the Tach.
My lense was plastic and it curved concave and was puting
pressure on the silver button in the middle and caused a sticking
at about 2500 RPM. Drove me crazy for weeks.
The way I could finally tell was when I looked at my reflection in the lense
I saw a very large nose (my own) .
I removed the plastic lense, re-cut a glass lense, and no more problems.

It surprised me that the tach lense was plastic because the gas gauge and
the speedo were both glass.

--- bill.

Check your wires, sounds like there is a short somewhere between the coil and the tach.

Mine used to do that. I'd just thwack it...It got the message.

KT

QUOTE (trekkor @ Jan 14 2005, 07:15 PM)

Mine used to do that. I'd just thwack it...It got the message.

same here. every time he does that i just knock on the glass to wake him up, and usually he get's right back to work ...

Andy

You can check your points too (assuming you have them) or install a new set. The tach is somewhat picky about the voltage waveform off the coil.

The tach picks up pulses from the coil. Perhaps the tach wire is picking up strong pulses from some other source at a fixed frequency. Or try swapping parts in the area of the coil and distributor. Two tachs that agree on a problem indicate a signal issue.

Tach wire too close to a spark plug wire?

I got nothin'.

The lenses are in the wrong way and it binds on the center button. I thought it was just mine but, you guys have the same problem. Is it worse when hot? Mine was. I took out the lense and found a pin prick sized area where it rubbed. I reversed my lense. No problem since. Maybe the tach maker was new or drunk or something.

Probably just a design issue. They must have made the concave to break up glare. Probably a bunch of lenses were out of spec or the center buttons were too big and rub.

Dave

Just stick an Autometer Monster tach in there and it will solve all the problems

IMHO the stock tach is only good for a stock engine....barely.
I got rid of my bouncing POS long ago.

Sorry to hijack... but my tach gets stuck at 7k RPM.. darn my engine is fast I thought... I guess I have to get a new one... ANyone got a silver center tach?

QUOTE (cmolina @ Jan 15 2005, 01:33 PM)

Sorry to hijack... but my tach gets stuck at 7k RPM.. darn my engine is fast I thought... I guess I have to get a new one... ANyone got a silver center tach?

i might.....