Tach stuck at full rpm on 86 Iroc-Z
Thread Starter
Junior Member
Joined: Sep 2009
Posts: 35
Likes: 0
From: Houston, TX
Car: 1986 IROC-Z28
Engine: 5.7L L98
Transmission: 700R4 OD
Axle/Gears: B&W 3.27 Posi- :D
Tach stuck at full rpm on 86 Iroc-Z
I have a tach problem on my Iroc. Whenever i start the car, it jumps to full rpm (being 7000 rpm) and is stuck there the whole time the car is on until i turn it off. Is it wired up wrong or is something just bad in the gauge or something? I dont have much knowledge in this area of problem.
Supreme Member
Joined: Jan 2006
Posts: 3,341
Likes: 10
From: Mooresville NC
Car: LOWERED ♦ CRIMSON METALFLAKE
Engine: ► 400 KUBES ◄
Transmission: 765R4
Axle/Gears: EATON POSI 4.56
Stuck Car
Your problem is in the circuit inside the dash that moves the pointer.
It’s contained on a small plug-in PCB or integrated in the main board.
On the PCB you’ll see a resistor chip.
Desolder pins 4 & 10.
Use a 500K potentiometer.
Solder it across traces 4 & 10.
Move the potentiometer to half way.
Start the engine and compare the tach reading with a test equipment quality tach.
Dial it in, unsolder one side of the potentiometer, measure it and install a matching resistor.
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
Happy Racing!
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
If People Drove Any Slower They’d Be Going Backwards
When you see fog lights on in good weather beware. Low performance driver ahead.
How bout those nitwits too scared to drive without headlights in the daytime,
and the nitwits that need headlights for a little rain
.
.
It’s contained on a small plug-in PCB or integrated in the main board.
On the PCB you’ll see a resistor chip.
Desolder pins 4 & 10.
Use a 500K potentiometer.
Solder it across traces 4 & 10.
Move the potentiometer to half way.
Start the engine and compare the tach reading with a test equipment quality tach.
Dial it in, unsolder one side of the potentiometer, measure it and install a matching resistor.
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
Happy Racing!
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
If People Drove Any Slower They’d Be Going BackwardsWhen you see fog lights on in good weather beware. Low performance driver ahead.
How bout those nitwits too scared to drive without headlights in the daytime,
and the nitwits that need headlights for a little rain.
.
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