 
     |
| 3800 w/Gauge Fix Not Working (Page 1/2) |
|
rbell2915
|
SEP 14, 01:47 PM
|
|
|
Hey there! I have a new to me 3800SC Formula and I just did the temp gauge fix on the cluster side. It no longer pegs on start up anymore. Unfortunately, the gauge says at 100 degrees and does not move. Do I need to switch the wires at the coolant sensor or do something else? Thanks!
|
|
|
|
1985 Fiero GT
|
SEP 14, 02:31 PM
|
|
| quote | Originally posted by rbell2915:
Hey there! I have a new to me 3800SC Formula and I just did the temp gauge fix on the cluster side. It no longer pegs on start up anymore. Unfortunately, the gauge says at 100 degrees and does not move. Do I need to switch the wires at the coolant sensor or do something else? Thanks! |
|
Yes, one wire is a simple switch, the other is the gauge, if you switch them in the the cabin you need to switch them on the engine too.
|
|
|
|
rbell2915
|
SEP 23, 05:17 PM
|
|
|
I switched the yellow and green wires on the three wire 3800 connector and left the low reference wire alone. The gauge doesn't work, but the temp light now starts to turn on as the engine warms. What next? I cannot switch the wires back in the cluster because then the gauge will start pegging again.
|
|
|
|
olejoedad
|
SEP 23, 05:23 PM
|
|
If you are using the GM three wire temp sender, the yellow and black wires go to the PCM and the PCM controls the temp light and cooling fan.
The green wire is the sender for the gage.
|
|
|
|
rbell2915
|
SEP 23, 05:29 PM
|
|
So what do I need to do? What wires am I swapping and what stays the same?
|
|
|
|
olejoedad
|
SEP 23, 08:19 PM
|
|
Terminal C should be for the gage, green wire.
The Black and Yellow wires go to the PCM, and are not used for anything else.
The PCM has outputs for the HOT lamp and the cooling fan.
Explain what you did for the pegging gage fix.[This message has been edited by olejoedad (edited 09-23-2025).]
|
|
|
|
rbell2915
|
SEP 23, 08:45 PM
|
|
|
I swapped the wires in the cluster, and I swapped B and C on this plug. But it appears either that was wrong, or I must swap the wires at the C500.
|
|
|
|
olejoedad
|
SEP 24, 09:06 AM
|
|
Put B and C back where they were.
That will make your temp gage get the correct signal.
Swapping wires at the cluster only prevents the gage from seeing ground at KEY ON.
If you haven't swapped wires at the C500 for the gage and HOT lamp signal, go ahead and swap them.
Your PCM should control the HOT lamp via an output that provides the ground for the lamp circuit.
|
|
|
|
rbell2915
|
SEP 24, 06:10 PM
|
|
|
Great, I swapped the wires at C500 and it wasn't too bad. Tomorrow I'll solder in the new ECT plug and pray it works!
|
|
|
|
olejoedad
|
SEP 24, 06:41 PM
|
|
| quote | Originally posted by rbell2915:
Great, I swapped the wires at C500 and it wasn't too bad. Tomorrow I'll solder in the new ECT plug and pray it works! |
|
It's not hard to repin the 3 wire plug...
|
|
|
