89 tach reads 1000 rpms high at 6000 but is close at idle?
03-03-2010, 11:37 AM
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Car: 1989 IROC-Z
Engine: 383 waiting on afr 195 comps
Transmission: T-56
Axle/Gears: 3.42 Posi
89 tach reads 1000 rpms high at 6000 but is close at idle?
I have an 89 iroc z and it has a t56 so my tach is kinda important. I have read through the 91-92 tach fix threads but I need to know how to fix an 89. The tach seems to read close at idle but sweeps pretty fast through the rpms. The 91-92 fix thread mensions a capacitor fix but I cant find and info on the earlier tachs. I'd like to know if I can do the resistor method or if there is something specific I need to adrress about 89 model.
03-03-2010, 12:00 PM
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Car: LOWERED ♦ CRIMSON METALFLAKE
Engine: ► 400 KUBES ◄
Transmission: 765R4
Axle/Gears: EATON POSI 4.56
Get The Tach Back
The 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 the potentiometer, measure it and install a matching resistor.
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
Happy Racing!
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 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 or “running” lights on in good weather beware. WLow 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
.
.
If People Drove Any Slower They’d Be Going BackwardsWhen you see fog or “running” lights on in good weather beware. WLow 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.
.
03-03-2010, 12:09 PM
#3
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Car: 1989 IROC-Z
Engine: 383 waiting on afr 195 comps
Transmission: T-56
Axle/Gears: 3.42 Posi
Re: Get The Tach Back
So you're saying its the same fix as the 91-92 tachs
03-09-2010, 08:52 AM
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Car: 1988 Iroc
Engine: 5.7L
Transmission: '96 T56, Hurst Shifter, Mech VSS
Axle/Gears: 3.45 9 Bolt
Re: Get The Tach Back
The 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 the potentiometer, measure it and install a matching resistor.
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
Happy Racing! ◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
Happy Racing! ◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
If People Drove Any Slower They’d Be Going BackwardsWhen you see fog or “running” lights on in good weather beware. WLow 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
and the nitwits that need headlights for a little rain
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