The large, friendly, speed display does not dim when the headlights are on.
Grumble.
Let me check my notes...
Oh, I see.
I didn't see that I needed to add a wire to the C1 connector that leads to the parking light circuit.
Luckily, it's a simple splice to the light switch mere inches away and easily accessible.
The hilariously wrong tach is because there's a resistor pack dealie on the board that decays with time. This is likely also what was wrong with the speedometer in the Olds cluster.
I've found a diagram for the pack and some instructions that tell us that if we bypass terminals 4 and 10 in the pack and put in a 500k multi-turn potentiometer we can just dial in the correct resistance and tune it right up.
Grumble.
Let me check my notes...
Oh, I see.
I didn't see that I needed to add a wire to the C1 connector that leads to the parking light circuit.
Luckily, it's a simple splice to the light switch mere inches away and easily accessible.
The hilariously wrong tach is because there's a resistor pack dealie on the board that decays with time. This is likely also what was wrong with the speedometer in the Olds cluster.
I've found a diagram for the pack and some instructions that tell us that if we bypass terminals 4 and 10 in the pack and put in a 500k multi-turn potentiometer we can just dial in the correct resistance and tune it right up.