nvu

If it's the old school manual air, check the pressure sensor. It's somewhere on the condenser high line. Short it and see. The temperature sensor is some feedback transistor, you can't short it to test. Unlikely as it only cuts out when the temp is too cold. Unlikely the AC switch itself is bad, you can bypass it and force AC on by turning to full defrost. No idea where to begin with the auto climate control, never had to deal with one.

If it's the single gauge one on the low side only. Yes it would read high, around 80-90psi when the system is off. Not much else to add about why it's not kicking on, but it's normal to see it high on a single gauge reading. Thinking it's more electrical than a system problem. Did you swap the relay with a similar one on the car yet?

Not sure, haven't had one break on me. Quick search on the internet seems like idosubaru has been through it before. He's on this forum too... https://www.subaruoutback.org/threads/repairing-captive-nut-failure-lots-of-complications.151202/

Swap in the used pair, it's less hassle. But also measure the length of the front bushing on your car and confirm first. The swaybar mounting tab may be different too, make a note of it. Figure out if you want to get those Delphi bushings and build a spare set later. Also pray to the rust gods that the big bolts don't break the captive nuts in the frame when you try and remove them. If it's the original bushing on the car, chances are the nut inside is corroded, I'd recommend completely relieving pressure on the arm by removing the knuckle before breaking loose bushing bolts.

oh right, if it's 2.5 electric throttle. the tps is in there but not easily replaceable, you have to adjust the set screw for it and have an ecu data reader. though, i've never heard of a tps failing on those style of throttles. they either completely fail with the motor not working or make a terrible grinding noises if the gears are sheared. the tps part is pretty reliable

2005 nonturbo should be cable throttle, it should be on the opposite end of the where the cable throttle goes and replaceable.

Odd, it should not kick off from charging at all for these models. There's no ecu control if it's 2 wire so no way to tell it to power off. Do you think there's a corroded wire in the harness causing intermittent charging? If you have a spare connector, dash lightbulb, and a switch, you could make a dongle from the alternator to the battery + and manually force the alternator on to test.

It should work. Only models I know need all 3 pins on the alternator were the sti and XT models with the 32bit ecu, electronic throttle. If yours is cable throttle, it's the old style and only uses 2 of the 3 pins.

I went reverse, 2006 alternator in 98 impreza. Swapped from black rectangle to green oval plugs and works fine. Though 13.5-14v at the battery is kinda of standard nowadays, it's okay for newer batteries.

If there's air, theres a leak. Check the lines for wetness and under the clutch reservoir. Get a scredriver and depress the slave piston in so you can wiggle the clutch fork back and forth. It should only move in two directions. If it's flopping all over the place, somethings broken, bearing, fork, pivot pin.

Other places to check. If near the rear passenger, check the pcv hoses. If turbo, theres a middle block nipple that likes to leak when the clamps weaken from heat.

I don't know for sure but suspect eyesight equipped vehicles need this step. I heard it's a nightmare to replace windshield glass with an eyesight system and it needs some special alignment and setup again. Not something any windshield shop can do.

I vaguely remember a youtube video about having to hook a computer up to the car and set something before installing the brakes. I'll see if I can find it again...

Try steering with the fill cap off and see if tiny bubbles apear. If so, likely the S shaped hose from the reservoir to the pump has gone brittle and sucking in air at the pump nipple.

There's a module you unplug to turn off the DRL permanently. On an 02 impreza it's passenger side glovebox/footwell area near the fuel pump relay. It's probably the same area on your legacy. Download the service manual for your car and find out.