525efi, gaffrig tach less than one year old and checked all my grounds on tach and engine block. At idle its 300 rpm off and at 4000 rpm its reading 5500 rpm, the more rpm the more its off. I had scan tool hooked to it to verify proper rpm. Any ideas?

Is it set up for a 6-cylinder by mistake? Your readings are proportional, so it looks like a setting is off. Is there a switch on the back, or dip-switchs?

exactly

I have checked the dip switches and they are correct unless they are marked wrong and I have checked the engine harness plug also. Technical support from gaffrig is 0, they just want me to send it in.

Throw the Gaffrig in the junk pile and buy Autometer Marine gauges ....... Don't take a chance on the tach giving you the wrong reading at the wrong time !!!!!


Jim

rw,
Does the scan tool use the same signal as the tach ?? Do you have another tach you can hook up in place of yours to see if the problem changes ? An ignition system that is missfiring can send extra pulses to the tach, making it read high.

I would double check the grounds, to the point of even rigging a jumper wire from the block to the back of the tach. Almost every tach problem I have seen on cars has been due to a poor ground.

I will second what the others said, if you do have to replace it Autometer is the way to go.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md