ghettocruiser

iTrader: (17)

Haha ooooohhh... I thought you were having problems... You were just anticipating problems... Just hook that sucker up without the 12v + resistor first. You will probably be ok. If not, do the trick. But Ide definetly try it without first.

chrisp3

Just a note on the tach settings. This would depend on which Autometer gauge you are using.

The 4 cylinder setting would not be correct on the "Ultra Lite II" gauges. The 6 cylinder setting is correct for this model.


ChrisP

tirefryin_s10

iTrader: (3)

I had to use an autometer tach adapter on mine in order to get any signal and its wired into the coil signal wires

Heavy85

Does someone have a schematic or thorough description of exactly where the resistor and 12v goes? I started it up for the first time a couple days ago and the tach did not work so I'm thinking I need the pull up voltage. It's a really old Autometer with the wires you have to cut.

Thanks
Cameron

busta9876

iTrader: (3)

I've used 680 ohm resistors with same result. I've found most of the 99-00 pcm's tach signal works fine with no modifcation, but 12200411 and all 2003 up pcm's need this modification done.

Today I was working on an offroad buggy with a 99 vortec 4.3L, I had to add the resistor to its tach signal to make it work.

If you read the descriptoin in GM service infomation for the instrument cluster, it states tach signal is brought in via serial data, but the engine speed signal wire is there for back up purposes.

I was able to change a setting with Tunercat OBD2 to make the tach work on 8 cylinder setting. I did not want to cut the wires on my tach. There is a setting about tach signal high & low pulse devisor. The stock setting is 6, I switched it to 3 and engine speed is right on with my laptop datastream. Now I did this on my stand alone engine swap, nothing else is hooked to the engine speed signal wire. I"m not sure how chaning the pulse devisor would effect anything else in a factory install.

I'd guess the reason GM uses a 4 cylinder tach signal is that they can make all the tachs the same, and program the PCM's to output the correct signal for whatever engine it is running.

Aston Tibs

iTrader: (3)

Pulling this thread up from the dead. I wired my Autometer tach with the 1K ohm resistor like Busta9876 did above. My tach works fine as long as I am not accelerating quickly. However, the other day, when I was drag racing my tach was bouncing like crazy to where I couldn't tell when to shift. Any ideas why? Do I need a different resistor?

Aston Tibs

iTrader: (3)

No one else has ever had tach bounce? I am running out of ideas here.

1964SS

iTrader: (1)

I never had an issue with my tach bounce, but mine worked without the pull up resistor to. I simply tied my autometer to the tach output of the Pcm and it worked.