tach stopped working, getting stumped
01-23-2014, 01:15 PM
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tach stopped working, getting stumped Ok, first off, it is an 04 GTO LS1 in a 93 mazda RX7. Got it running last year, everything working fine for the most part. The stock tach works on a 4 cyl signal, so all i had to do was wire in a 10k ohm pull up resistor to get the tach functioning correctly.
Towards the end of last summer, started getting some erratic performance from the tach. Bouncing, sticking, etc, until it finally completely crapped out.
It is pretty common on the rx7 to have the tach circuit board fail, so i picked up a used tach that was supposed to work. The tach is pretty simple, it mounts to the cluster with 3 screws, which also make the connections to ground, +12v, and signal.
Anyways, i installed the new tach and fired up the car, still no tach. i had an old cluster laying around with the older style tach in it that i know worked before, hooked that up, nothing.
I checked the mounting screws, had ground on the ground screw, +12v on the +12v screw, and a few volts on the signal screw. This tells me that my pull up resistor is still hooked up, i think.
I havent pulled the pcm from the kickpanel to check the wiring, but i dont see how it could be an issue.
Is there any way to test the tach output from the PCM? Is it possible the tach driver is fried for some reason? it seems a lot of people use the pull up resistor with out issue, but places like autometer say you should only use 5v not 12v.
Towards the end of last summer, started getting some erratic performance from the tach. Bouncing, sticking, etc, until it finally completely crapped out.
It is pretty common on the rx7 to have the tach circuit board fail, so i picked up a used tach that was supposed to work. The tach is pretty simple, it mounts to the cluster with 3 screws, which also make the connections to ground, +12v, and signal.
Anyways, i installed the new tach and fired up the car, still no tach. i had an old cluster laying around with the older style tach in it that i know worked before, hooked that up, nothing.
I checked the mounting screws, had ground on the ground screw, +12v on the +12v screw, and a few volts on the signal screw. This tells me that my pull up resistor is still hooked up, i think.
I havent pulled the pcm from the kickpanel to check the wiring, but i dont see how it could be an issue.
Is there any way to test the tach output from the PCM? Is it possible the tach driver is fried for some reason? it seems a lot of people use the pull up resistor with out issue, but places like autometer say you should only use 5v not 12v.
