Posted this in UTH, but maybe you electronics junkies can help...

I got an autometer cobalt series A/F gauge and have a few questions on install...
This is the wiring diagram from AutoMeter:


Since our dash lights are always on, and brighter during the day, can i put the red and white wires together? Anyone know of good wires behind the dash that are suitable for tapping these wires to? They are for 12v dash lighting and 12v ignition.

Is there a way to make the gauges dim at night and turn bright during the day, like our instrument cluster behaves?

Also, anyone who's installed this, what wire do you tap the purple one to? Not sure where our PCM signal wire is...

 

No. Red is to power the gauge. White is to power the light bulb inside the gauge.
Look at the fuse panel under the dash and you'll see 3 empty spade connectors. These are the ones you should be using. One is for power with igition and another one is for instrument panel lights - this one is controlled by the dimmer function). Ground can be found in the "octopus" of wires going to a large bolt on the frame above the fuse panel.

The violet wire is your O2 sensor signal. This one goes to the white wire on the ECU harness (I think the 31 pin connector) via a "T" connector.

 

wow thanks xviper, once again, you come thru for me

Regarding the 3 spade connectors in the fuse box. i believe my comptec water pump for the Aftercooler is using the one closes to the floor. That leaves 2 empty spade connectors... which one of those 2 is the dimmer? I can probabaly figure it out if you dont know it off the top of your head...

 

I hope you are using the under dash fuse slots for the "relay" for the water pump because if not, you may overload that circuit if you now splice in a gauge.
Here is a bad pic of those connectors (mine are all filled up):

Top left = lights
Middle = constant hot
Bottom right = hot with ignition
Note: The one for the lights activates only when the headlight switch is used. It will light on the first "park light" position.

Also, the white wire for the O2 signal is pin #16.

 

Here's a slightly less fuzzy pic of the connectors:



The IGN connector is fused through fuse 42, 40 amps, that powers everything on the ignition circuit plus HVAC and ABS. You don't want to blow this one.

The BATT connector is fused through fuse 42 too, but it's before the ignition switch.

The LIGHTS connector is fused (I think) from fuse 23, 10 amps, controlling the tail lights and parking lights.

 

thanks fellas... anyone have a pic of the white ECU wire that i should tap for the purple AF wire?

 

bump for finding the white wire!

 

Pull the 2 large connectors on the bottom of the ECU. The white wire is on PIN #16 of the 31 pin connector. The other connector is 32 pins, so very close.
In the central cluster of the 31 pin connector, you will see only 1 white wire. There are no other white wires near it.

 

thanks viper! found it! to my great happyness, the connectors are labelled pin 21, pin 32 and pin 31... so sweet The white wire is also the fattest wire on pin 31 connector.