New AC compressor

[Buzzard67]

Well I just replaced my alternator ( see other post).
While I was going to replace my alternator I might as well replace my ac compressor since it in the same area. I now have a break dash light on ( long story in other post, see below ). Long story even longer. The new compressor doesn’t engage. The ac button works , new belt and good fuses. The reason I bring up the new alternator is because the new ac is not engaging. Could any of this be related?
Let me know if you have any thoughts.

“Well the other day 3 dash lights turned on my Toyota Tercel DXL 84. Temp, battery and break light.
Was able to drive home and park it. Ordered alternator, installed alternator and new belt. Also noticed my positive battery clamp needed replacement so I did that as well.
Car started fine, ran fine, lights off. The next day started up fine but now only the brake light is on. Checked fluid reservoir, full. Pulled hand break and light gets brighter.
I believe everything is working well. ( wiper,lights, fan, radio) no drop in power or preforming with all accessories on. Just that dang break light is on. I know it mean something, I just don’t know why it started after sitting overnight.”

[Paul]

Could it be low on refrigerant? The low pressure switch will keep the AC clutch from engaging.

[Buzzard67]

Not low on refrigerant or compressor oil.
Is there a way of jumping the low ac sensor and get it to engage?
If so where is it located at. Photos help.
Thanks

[Paul]

I answered from my gut... and now should eat crow. The pressure switch is shown on the liquid line before the expansion valve.

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Perhaps better to first check for 12v going to AC clutch when switched on. If power is present, then checking clutch lead wire for 3.7 ohms to ground to verify clutch coil.
On most cars with a low pressure switch, the compressor is protected from overheating due to low refrigerant by interrupting power to the AC clutch.
...and after further reading, this switch on the Tercel should be closed with more than 30 psi pressure on it. You could meter it behind the glovebox and make sure the switch is closed.