reset rpm gauge on 08 altima

While accessing the BCM behind the instrument cluster on my 08 Altima, I accidentally removed the clear cover of the gauges and pushed the RPM needle down a bit. If I am driving now what should be 1800 rpm shows barely over 500 rpm. Does anyone know how to reset it?

If the needle is below the 0 rpm when you will need to rotate the needle clockwise to the stop and move it past the stop point an amount equal or greater to the amount you pushed it. If you move it to far the other way you will just move it the same way you put it out of adjustment the first time, until it zeros.

out of curiosity: is it posible to verify the rpm using the tach signal?

If you have a volt meter that can read frequency you can calculate frequency based off of the tach signal. You will have to scale the frequency to the proper RPM. If you use a fuel injector for a tach signal you can fairly easily mathematically calculate what frequency is equal to what RPM.Kevin Pierson

If the tach signle is a one to one you will be fine but if the factory tach isn't one to one then it will be using a divider to match the vehicle output to the tach input. So it depends on the design of the tach and the chipset that is used if any. As far as what it is you will have to hope someone else has done the needed research or you will need to do it yourself.

If you go to an injector the math is pretty easy. Frequency is measured in seconds, and RPMs are measured in minutes, so multiple your frequency by 60. Since your injector only fires once every other revolution (suck, squeeze, bang, blow)you need to multiple by 2. So RPM = Frequency of fuel injector x 60 x 2 Kevin Pierson

So I tried to move the needle back to zero (felt some resistance, assuming that's good) and it seems to show correctly after the initial startup. But when I shut the engine off, the needle falls back to below zero. About measuring the RPM's, I connected a DMM (measuring hertz) to the tach wire and it gave numbers ranging from 20 to 45. It would show a number, zero, different number, zero and so on.

You need to check the position with the ignition on, and engine off for the zero point and adjust to that.

Just tried that lurch. Worked with the first two starts in fairly quick succession. Next start (after aprox. 3 minutes) back to square one.