I am working on the sunbird cluster upgrade into a fiero I know about how the tach might need to be changed but do I need to make another circuit for the speedometer or is it plug and pray, wire 1 for 1

A BOOST
B Not used
C
D
E
F
G
H
I
J
K GROUND
L LAMPS
M SEAT BELT
N OIL PRESSURE
O FUEL LEVEL
P IGNITION PWR
Q LEFT TURN
R TEMP
S ajar
T not used
U BRAKE WARNING
V service engine
W SPEEDO
X RIGHT TURN
Y HIGH BEAM
Z TACH

C3 connector
1 - not used
2 - Q
3 - not used
4 - X
5 - P
6 - not used
7 - O
8 - M
9 - P
10 - S or v
11 - K
12 - Y
13 - not used
14 - U
15 - not used
16 - not used
17 - N
18 - Z

C2
1 - not used
2 - not used
3 - not used
4 - K
5 - not used
6 - not used
7 - L
8 - not used
9 - not used
10 - Ajar (unk)
11 - R
12 - not used

C1
A - L not used
M - W
N - not used
P - K Ground (unk)
R - VSS low (unk)
S - VSS high
T - not used
U - signal to cruise module (unk)

[This message has been edited by mmeyer86gt/gtp (edited 12-15-2014).]

I Don't know about the Sunbird in particular but where you run into issues with the speedometer is that cars from that era had external speed buffers whereas new cars have that built into the ECM. The Fiero was unique among all cars I'm familiar with in that the speed buffer was built into the speedometer. In other words if you connect the output of the VSS directly to any speedometer you will not have a speed buffer and your you will get erratic performance if anything at all. The buffer converts the analog signal from the VSS to a square wave that is happier driving a speedometer. In the 80s cars it was a yellow box somewhere up under the dash, you can easily add one.

Now having said all that I don't know if the Sunbird digital cluster has a speed buffer built in or not. If it does then it's a wire for wire swap and Bob is your uncle.

Everything on my FIERO is plug and PRAY.

WICKED

quote Originally posted by mmeyer86gt/gtp: I am working on the sunbird cluster upgrade into a fiero I know about how the tach might need to be changed but do I need to make another circuit for the speedometer or is it plug and pray, wire 1 for 1

I gotta use that one at work...