74 260z tach problem!

[deedee]

when the car is off the car at the tach registers at o. But when I turn on the car the tach jumps to the highest number 8 or 9 but when I'm driving the needle stays at 8 or 9 and doesn't move. As I turn off the car the needle goes down to 0.What is wrong with the tach?

[EScanlon]

Ouch! I hate to say this, but in my experience the tach got fried. There's a difference in voltage from the "upper" circuit board to the "lower" board and if you accidentally short them (by inserting a screwdriver from the back) you'll fry the resistor/transistor (not sure) between the two boards. I did that to one of mine (checking if the tach was "adjustable") and unfortunately, it toasted it beyond recognition of what it was, making it impossible to replace. Once it "zapped" this is exactly what it would do, Ignition ON tach to it's maximum, and back to 0 when ignition turned off.

I hope that this is NOT the case with yours. Maybe some other member can post some thoughts also.

E

[deedee]

It's funny the last 2 to 3 days my tach as been funny. The tach will register for a little while and then bounce around and then yesterday starts doing the same thing. 0 at off and 8-9 when on nothing inbetween. Could it be a loose ground in the dash?

DeeDee

[Virto]

You probably have a dead tach. Arne just posted a similar issue in another thread and the general consensus is that the tach bit the dust.

Before replacing it, I've noticed you have posted a number of electrical issues...you may want to concentrate on the electrial problem first and make sure that they aren't related.

[KenshinX]

My tach does the same thing and the whole car gets weak when turning on the lights. Someone said that the car needs to be rewired and I believe the tach has been replaced before because the previous owner left me a box of parts and a tach was in it. Becuase of this electrical issue my Z isn't running right now she wont start.