OK this is for second gen trucks, but the principle is the same for any vehicle.
NOTE/DISCLAIMER: I will NOT be doing a super detailed how-to on this a/c repair.
this repair requires you to know what you are doing to prevent damage to the a/c system, so i wont be going into detail on how to remove the a/c from the engine...etc. if you cant figure that out, you probably shouldnt be working on a/c. basic mechanic skills needed to physically replace the parts. Proceed at your OWN RISK!! if you are new to a/c repair READ this thread A FEW TIMES BEFORE ATTEMPTING REPAIR!!! This how-to is based on a/c compressor failure/general leak and the process to fill the system.
OK now that is said and done here are some PDF files i acquired.
This is the general fill up and recommended pressures @ temps on page 10.
This one is more of the overhaul, BOTH contain/cover the same info, but its good to have both. it may say "preview not available" but you still have the option to download it. this PDF should cover any repair not listed in this how-to.
So, finally did the a/c on the ZR2 and decided to do a writeup about it, being summer is here and a/c questions are always being asked.
i purchased the A/C manifold gauges from Harbor Freight for $40-60. it does the job gauge wise as it's accurate, but yeah the knobs are fragile so don't crank down on them to close the valve. compressor... either buy new OEM, or a good new aftermarket, rebuilt compressors don't seem to last as long.
The system in the 2nd gen trucks hold 28oz of 134A, and 8oz of PAG oil. use the PDF above to see more information on the system specs.
- A/C manifold gauges
- 28oz 134A
- PAG 150 oil (or whatever your compressor comes pre-filled with, make sure you check that. use what the compressor comes with, flush out the old oil.)
- a GOOD vacuum pump (CAN BE RENTED AT AUTOZONE WITH THEIR RENTAL PROGRAM. ITS FREE!!)
- A/C compressor
- O-ring kit
- orifice tube
- basic hand tools with some decent sized wrenches
So here are the materials gathered.
first, make sure the system is completely empty unless it has already leaked out. a shop with a recovery machine can remove your old 134A if the system still holds pressure.
second, remove the intake...2.2, or 4.3 you will need to do this. again, if you cant figure this part out, stop and seek a professional to complete the repair or READ the PDF above to learn more about the a/c system and removal procedure.
Remove the serpentine belt, then remove the compressor, 4 bolts attaching it. and the a/c lines and the clutch connector up front. on the 4.3 models the high pressure switch is located in the back of the compressor, so don't forget to unhook that before removing the compressor.
4.3 owners, Chances are your new compressor will NOT come with a high pressure switch....so flip your old compressor over and using a snap ring tool, remove the high pressure switch and install it on your new compressor. the new compressor will have a plug, as shown below. remove and install the switch here. clean any debris from the switch to make sure it seals. or buy a new switch if you suspect the old one to be bad.
where the old is leaking. generally these compressors leak in the middle. you could wash the compressor/oil off with water and see if oil appears, if so, you have a leak. discontinue further use of the compressor to prevent more damage to the system.
Thought i heard a loud hiss when turning the a/c on one day. apparently some 134A/oil blew out lol.
using a pair of channel locks i kept the hardline/accumulator steady. its VERY IMPORTANT YOU SUPPORT THE ALUMINUM LINES WHEN REMOVING THE FITTINGS. FAILURE TO DO SO WILL CAUSE THEM TO BEND
simply unscrew the low pressure switch from your old accumulator (if still in good working order) this repair can be done on a fully charged system as there is a schrader valve to keep the pressure in.
orifice tube removal. it is VERY important you change this. the screen easily clogs, and is critical for proper a/c operation (and its cheap). it is located on the bottom of the evaporator coil, by the frame. needle nose pliers are needed (or a special tool) to remove it. it should come out easily. again, support the lines when removing the nut on the line. replace O-ring.
some metal shavings, but not bad. I've seen worse lol. now, if your orifice tube is packed with metal shavings, i suggest you replace the condenser up front. most likely its clogged with metal shavings as well and if you don't replace it, the orifice tube will just get clogged again and introduce contaminates in the system. i believe they sell for $120....a lot cheaper than a new a/c compressor/charge and would be cheap insurance....or just ignore what i typed and go ahead and don't replace it....see what happens
if you have nitrogen available you can blow out the lines to free any possible debris.
i grouped the O-rings for easier matching. that single black o-ring was a stock one. make sure you get the correct one and replace every o-ring from any connection you remove. you could replace ALL the o-rings but if its not leaking you don't have to...but that is a chance you will have to take, as the old ones could start to leak. lubricate the o-rings with mineral base 525 refrigerant oil...but if you cant get any you can use mineral oil to lubricate the o-rings...also heard dielectric grease works too but i don't know if i would use that. don't use pag oil to lubricate the o-rings. it attracts moisture and can corrode the fittings (or from what i have heard) make sure you do not torque the crap out of the lines! doing so can cause the fitting to leak too. just make sure its fairly snug, but dont force it.
If your compressor is shipped with oil, and its 8 oz, leave it. if your compressor was NOT shipped with oil, add the correct amount of pag oil to the system. refer to the PDF above for this info. rotate the compressor 10-20 or so times once installed to cycle the oil throughout it.
next, draw a vacuum for 40 minutes. suppose to be 30, but whatever, doesn't hurt if you do it a little longer. make sure you open the high, and the low side on the gauges and the valves are open on the quick connect. the valves on the quick connect you tighten down to open, sorta opposite, but it pushes down the valve on the line.
Close both high/low valves and turn the vac off for 10 minutes for a quick leak check. there was none
. so let it sit for 20 more minutes to confirm no leaks. i do know some leaks can not leak on a vacuum, but can when pressure is present. also there is a chance the A/C manifold gauge could leak, or the quick connect... something to keep in mind.
So, now its time to fill the system with 134A. a hot pan of water helps prevent the 134A can from freezing. DO NOT TURN THE CAN UPSIDE DOWN WHILE FILLING
!!! This could damage the compressor.
- start the truck
- turn the a/c on max
- fan speed 4 or max.
slowly open the low side valve, DO NOT OPEN THE HIGH SIDE AT ANY TIME
!! this will cause the can to pressurize dangerously and could EXPLODE
. you are dealing with 150-300 PSI from the compressor going into a can that is not designed to hold such pressure.
so, the system would be filling up with 134A, the compressor wont be running at this time, but once the pressure builds enough it will kick on for a few seconds and shut off, and keep cycling slowly. every time the compressor kicks on, it draws in 134A from the can (it will get cold) you will also see the pressure increase on the high side, and the low side pressure dropping while the compressor is on.
after the first can the compressor should be running constantly, for the most part. the late model 4.3s and 2.2 have a variable displacement compressor, so they do not cycle on/off during operation.
after the second can the system should be blowing cold, open the 3rd can and use a digital scale to weigh it, add 2 more oz of 134A to fill the system. Refer to the pressure tables in the PDF for the correct high/low pressures. take note of the current ambient temperature, and humidity and follow the chart. page 10 of the first PDF will have it, as well as the second pdf. with ~28oz of 134A in the system, and at 1500 RPM with the A/C on max, and the blower speed maxed, the pressure should be very close to what the PDF files state.
Rev the engine to 1500 RPM as per GM manual. had to get creative LOL. you can fill the system at idle, but to get the final reading you need to do this step.
, on Flickr
it works! (forever alone
close the valve on the high/low port quick connects, and remove. leak checking the high side port with some water. Sometimes, these leak, so it wouldn't hurt to replace the valve. on the high side port it simply screws off, it looks like one piece on the hardline, but in fact 2 pieces. make sure you use a wrench to hold/support the line before removing the port. the low side port likes to leak sometimes. even with a new accumulator/dryer. i use a pair of needle nose pliers to gently pull the schrader valve out. this should stop any leak at the valve. it also wouldn't hurt to run the a/c while checking the high port. as the greater pressures would likely cause a leak if one is present. using compressed air, remove the water from the port and let it dry before installing the cap.
nice and healthy system sweats.
So hope that will help you guys getting A/C to work. please, do some reading before attempting this job. its easy once you get things figured out and understand. by no means am i a "pro" at a/c systems. but i do have enough knowledge to work on them. please, if anyone has any questions or suggestions, post your thoughts.