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.

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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



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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.

Next step then is to Ing. on motor off, remove the needle as it is just pushed on the pin and reseat it in the correct position. You may have loosened it up when it moved the first time and now it's not completly seated on the pin.

Is that a delicate procedure? Anything I need to be extra careful about? Don't want to break something else in the process of fixing it

Pull staright up on the needle at the center. A metal fork works in a pinch to get under it at the center and lift.

I tried pulling at the center of the needle. It doesn't come off easily. Is the needle sitting fairly tight on the pin?
Lurch you seem to be very knowledgeable about this. Have you done this yourself on a Nissan?
Thanks for your input so far.

No not a nissan but all analog guages are put together this way with the stencial or back ground and needles placed on the pins. You can try and reset it again and then push down on it to see if it came off the pin alittle when you bumped it.

I finally got it to work. It is a somewhat delicate procedure to take off the needle and even more to put it back on without moving it in the process. My advice to anybody who will have to do that as well: take your time and don't bend the pin that turns the needle, it's only about a 1/32" in diameter.
Kept an eye on the gauge for the last couple days to make sure it's fixed before posting this. Thank you lurch228.

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"Good judgment comes from experience. Experience comes from poor judgment."
-unknown

Your welcome.