I'm sorta self taught on this a/c stuff but there is a ton of info online. The light is the a/c low system pressure indicator. It will come on when the a/c system has 3psi +/-
and protects the compressor from running without oil.
What does your gage set system pressure read? High and low pressure gages will be the same when the compressor is not running.
Find the leak and fix it, generally good practice to replace the expansion valve and drier if the system has been low or open to air for any period of time. (moisture in the
air ruins the drier and that leads to plugged or stuck expansion valve)
I just did the air in my 7140, autozone rents/loans out a vacuum pump, gage set and flushing tool. I was surprised how much crud was in the evap and the line between the drier
and the exp valve (the valve was plugged and didn't work). Autozone sells the flushing fluid, but some online use mineral spirits. I did the first flush with min spirits, then
flushed that out with the a/c flush stuff.
Toughest part of the job for me was getting the old valve out after lifting the cab off. The drier is under the floor near the door, above the battery and is fairly accessible.
Flare nut wrenches would be nice but not absolutely required.
Get the right o-rings, R134 systems use HNBR material rings, or just get them from the dealer when you buy the other parts.
Good luck, but if you're not comfortable with doing this find someone that is and help them. It isn't hard work, just different thinking...
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