96 corolla --1.8 engine -- AC button does not light / 4 upper pins and 1 lower left pin inside button.
Get 20 ohms on upper left and lower left pin only.
No volts at relay, but I don't know what button should read if it is good.

It should read infinity when the button is "on" across at least 2 poles.

Yes I have infinity across 2 and when the button is pushed in I get .3 ohms on 2 or the upper right

It seems I should have voltage across several leads for the relay under the hood, but button in or out nothing shows.

Trying to find out why compressor clutch won't work.

Are all fuses in good working order? Is there fluid in the A/C system?

Fuses appear to be good.
Had a compressor with bad bearing, so replaced it today, and tried to put R134 in, but can't get compressor to run, so I'm stuck.
Checked plug to compressor, and only reads resistance.
Read 4 leads to low press switch, and only 1 lead has 14 volts, other 3 have resistance.
Fan runs when low switch is unplugged, and stops when re plugged.
Trying to figure out how to troubleshoot non voltage lead on plressure switch.

I found the problem ---
There are 2 - 15 amp fuses located each on the right and left pasenger side below the dash.
Both were blown.
Now AC switch light comes on, and compressor accepted freon, and car blows cold air.
Now I can sell it.

Good luck with the sale. Glad you got it fixed.