dlr944

I tested the reference and speed sensors. Both speed sensors tested perfect per Clark's Garage test procedure. Next I pull out the gauge and check grounds and connections. However since this gauge works off a square wave, has anyone seen this before?

Thanks

Humboldtgrin

Sounds like a house of pain, do you drive on cypress hill? I hear things jump around there. I couldn't help myself.

dlr944

Should the tach needle have more of a damping effect when falling? Perhaps the internal windings are woren out?

odonnell

The tach is actually driven by the ignition coil pulses in our cars, so if your car is running fine, the tach is probably the issue rather than the signal it's getting.

968workaholic

The tach signal is generated by the DME and then goes to the tach. Completly different wire than the trigger wire that runs to the coil. Does the needle always "bounce" at the same spot?

Tom M'Guinn

True, though the tach does use the same dme ignition pulse that is sent to the KLR for timing adjustments, then returned to the DME to create the coil-level pulse. So if the tach signal were bad (at the DME), so would the signal to the coil... I'd be inclined to check all connections including the edge card behind the instruments, the little football connectors on the back of the cluster, and the connector in the footwell that carries the signal to the tach. If that's all good, I'l blow air in the tach, gently, in case there's dust or debris inside, and then maybe try a tiny drop of sewing machine oil on the shaft...

dlr944

Can anyone verify if the tach needle does not have dampening like the one in the video? I read a lot of VDO tach gauges have this issue.

Tom M'Guinn

I have a spare I can check for you in the next day or so...

dlr944

Thanks Tom. I am hoping your tach shows so dampening. All my other gauges do except my tachometer.

Tom M'Guinn

Can't do it today, but these two videos from prior testing might shed light...

Tom M'Guinn

here you go...

ECU Doctors

Great videos!

dlr944, how did you end up making up?

dlr944

Thanks for reminding me ECU doc. I ordered a used gauge from Lart. Yes my tach worked but something is wrong with the counter springs and it falls too sharply and then bounces. The one from Lart works like the one in Tom's video shows - manually moving the tach.

So for those that have a bouncing tach unrelated to the reference sensors; it's the internal windings. There are a lot of threads about tach bouncing related to starting issues/ref & speed sensors. Hopefully this thread will help someone down the road outside of the normal tach bouncing starting issue.

thanks Tom and Lart!