I need wiring diagram for 1999 chevy express 3500 van- the rear lights- brakes, trailer hookup, etc- please don't tell me to look in haynes manual or something bc i actually have that book and funny thing- that page happens to be ripped out- HA HA HA-NOT AMUSED. i appreciate it. thank you

if doesn't engage because is out of freon or low pressure switch is not working or disconnected other then that clutch coil is not good or is disconnected

Check the turn signal switch. Brake light power comes thru it before the brake light switch on the brake pedal

Recommend investing in a Haynes manual for your van:
Chevrolet Express manual

Vehicle electric trouble shooting is the worst. Some of the problems you described the bulbs may have multiple filiments with only some burned out. It may sound silly but change the bulbs. Get a couple of new bulbs and try them in the different spots. Time, road vibrations and spring pressure causes the contacts on the bulbs to wear until they get a poor connection then you get a little arcing that build up a residue and a bulb that test good doesn't work.
Your on the right track with the ground wire. Try a test lamp with a good gound connection and test the different sockets, if your test light works but your bulb doesn't you have a ground fault. If neither work check the switch and fuse before you start tracing the wiring. These are just general trouble shooting tips It's very hard to trouble shoot electrical problems sight unseen.

DRIVE BELT DECAL SHOULD BE UNDER THE HOOD.OR YOU CAN GO TO DEALERSHIP GET ONE AUTO ZONE OR ADVANCE AUTO PARTS CAN GET YOU ONE.OR YOU CAN BUY A HAYNES REPAIR MANUAL IT HAS BELT DIAGRAM.

454 with ac and a.i.r.

the wiring is pretty staright forward.
so connect
-white wire to a good ground,
-brown wire to parking light brown at left light assembly on the van.
-yellow wire to left turn/brake light to yellow at left light assembly
-green wire to right turn/brake light to drk green at right light assembly

that should do it. good luck

Go to an auto parts store and see if you can have a look at some electric brake modulators and trailer connectors they almost always have instructions in them that detail standard colors for any install. The standard diagram is often right on the back of the connector package.

Ask dealer if it has a towing package on it. If it does, you usually just pop fuse in under hood for electric brakes, and harness to adapt into is usually near or at rear bumper. Even if it doesn't have brake wire, you should still be able to install adapter at rear,for lights etc. which is available from dealer or auto supply places, then you may have to run electric brakes separate.

Chiltons or Haynes manuals have wiring diagrams for you. very clear to read. Autozones, Advance Auto, Murry's etc have these in their stores, Cheap insurance to have one.
Dan