91 Camaro Speedo and tach not working
06-02-2013, 12:39 PM
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91 Camaro Speedo and tach not working
Hey Guys new member here. I have recently bought a 1991 V6 Camaro with a automatic... The problem is weird and any help would be appreciated. Well I don't know if any of this stuff is related but the speedometer only works sometimes and when it finally does work it's real bouncy and my car goes from overdrive to drive constantly, but only when the speedometer does start working the transmission does that and the tachometer is pegged out wide open at all times and never moves. What have I bought here? I'm a student majoring in welding and this is my daily driver to school. Any help would be great. Thanks ahead of time
06-03-2013, 04:42 PM
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Car: LOWERED ♦ CRIMSON METALFLAKE
Engine: ► 400 KUBES ◄
Transmission: 765R4
Axle/Gears: EATON POSI 4.56
Weld Done
The problem is probably the VSS (Vehicle Speed Sensor) located on the transmission.
Connect an audio amplifier across the VSS and ground.
With the car on jackstands listen for a hum from the amplifier when the rear wheels are rotating.
Because the problem is intermittent the VSS might test good but under driving conditions cut out.
You can replace the VSS or further the diagnosis by gaining access to the buffer which looks like this:
It’s located behind the instrument panel at the right.
Connect the audio amplifier to terminal A yellow wire to make sure it’s getting a steady signal.
Ground to ground, the signal wire to terminal A yellow wire of the VSS.
While driving listen for the hum from the amplifier.
If you do, then find out if you get a hum from terminal C tan wire.
The tan wire then goes to the speedometer unit.
▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬
There is circuitry in the dash near the tach.
It’s contained on a small plug-in PCB or integrated in the main board.
On or near the PCB you’ll see a capacitor, replace it.
Also 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!
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
I Don’t Mind Wreckin’ On The Track, No Paperwork To Fill Out
Connect an audio amplifier across the VSS and ground.
With the car on jackstands listen for a hum from the amplifier when the rear wheels are rotating.
Because the problem is intermittent the VSS might test good but under driving conditions cut out.
You can replace the VSS or further the diagnosis by gaining access to the buffer which looks like this:
It’s located behind the instrument panel at the right.
Connect the audio amplifier to terminal A yellow wire to make sure it’s getting a steady signal.
Ground to ground, the signal wire to terminal A yellow wire of the VSS.
While driving listen for the hum from the amplifier.
If you do, then find out if you get a hum from terminal C tan wire.
The tan wire then goes to the speedometer unit.
▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬
There is circuitry in the dash near the tach.
It’s contained on a small plug-in PCB or integrated in the main board.
On or near the PCB you’ll see a capacitor, replace it.
Also 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!
◙◙◙◙◙◙◙◙◙◙◙◙◙◙◙
I Don’t Mind Wreckin’ On The Track, No Paperwork To Fill Out
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beachrodder
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