A/C compressor
 

Last night i turned on my A/C in my 2000 Taco- the compressor let out a loud squeal each time I turned it on- A
strong awful smell came from under the hood- assume the compressor relief valve opened..... Tried the a/c today
and it blew a little bit of cold air- would not take a charge- assume the compressor needs to be replaced? Truck
has over 215K miles- thanks!!

Look at the front of the compressor while you engage and disengage the A/C to see if the center locks in and spins or not? It could be the clutch is shot, but anymore they are cheaper to replace then to rebuild yourself.

What kind of smell??

From the slipping belt.

No such thing as a Relief Valve on the AC compressor that would defeat the whole idea

after checking to see if the compressor clutch is engaging and it isn't, you could also test the compressor and see if your low on freon by jumping the pressure switch with a paper clip, but a squealing compressor is usually a sign you lost your PAG oil and compressor needs replacing. replace the receiver dryer as well and have the system evacuated, vacuum tested, oiled and recharged.

clutch still engages- but still not able to take anymore R134- smell was almost like the R134 smell and burning metal- tested the pressures and the low side read about 20 lbs and the high side was just over 200