Maybe least important problem; Outside temp gauge

[driveslikejehu]

Not important but a curiosity. My outside air temp gauge in the Subaru dash doesn't work. I've chased all the wiring and it's all connected correctly- to what's still in the car. And the sensor seems to be working.
The wiring diagram shows some wires T connected to the AC Control Module, which is long gone. Seems something the dash computer is looking for its not getting.
Anybody have this issue and bothered to figure it out?

outside temp.jpg

[RPGs818SNA]

I don’t have your issue, but will try to help. The T connections to the Auto AC Control Module only apply to cars with automatic transmissions, but may have been present in your donor harness. They were probably snipped off. That leaves 5 wires of interest, 2 power, 1 ground, and 2 sensor wires.

Outside temp sensor schematic.jpg

On the combo meter, C10 (LR) is unswitched power and C7 (RW) is ignition switched power. C6 (B) is ground. B11 (BP) goes to the sensor, and B8 (BL) is the sensor ground. The sensor measures 1650 ohms. Unfortunately my combo meter is installed in my dashboard waiting for its turn to be installed on the car. (That’s why I kept reading OPEN on both sensor leads.) With the sensor unplugged, you should see some voltage on BP with the ignition on. BL should read a few ohms to ground.

To troubleshoot, I’d unplug the sensor and check it for around 1650 ohms. Then I’d check for voltage and ground on BP and BL with the sensor unplugged. Then you have to get to the combo meter connectors to check for power, ground, and continuity on the BP and BL wires to the sensor. If that doesn’t turn up anything odd, it’s likely a combo meter problem. I’m glad it’s not a critical function.

Good luck with it,
RPG

[driveslikejehu]

Thanks for the reply...
Yeah as noted all the wiring checks out. I don't see any connection to Trans module, but the connectors B282, B283 to the Auto AC module were there and connected as shown in the diagram. The YB wire from the AC module seems to be in the circuit in Combi meter- just don't know what its doing.
My sensor has similar but not exact resistance as yours, but does change with temp. Might try replacing it.

[RPGs818SNA]

You’re right, my mistake. The Auto/Manual refers to the A/C, not to the transmission. So your combo meter has the Auto A/C STI wiring shown on page A/C(A)-03.

STI AC schematic.jpg

The Ambient Sensor is just a thermistor. The combo meter sends a current and measures the resulting voltage to determine the outside temperature. If you’re reading something around 1600 ohms, some temperature should be displayed. Replacing it is easy, but I doubt it will help.

The YB wire appears to be a variable voltage output to the Auto A/C module so it knows the outside temperature and how hard to blow warm or cool air. The STI combo meter combines an output from the combo meter microcomputer and the ambient sensor and sends that down the YB wire. If YB is open, it shouldn’t cause a problem. If YB is grounded, that might pull the BP wire voltage down too low to be interpreted as a temperature to display.

The only other thing I’d try is, with the ignition on and everything connected, measure the voltage on the BP wire at the combo meter I10 (the middle Green one) Pin 11 or perhaps at the B36 to I1 (Blue) connection, which might be easier to get to. I can’t tell you what it should be, but it shouldn’t be 0 or 12 volts. While you’re there, I’d check the YB wire as well. It should be about the same as PB.

Good luck,
RPG