A/C compressor replacement

[smdk2500]

IIRC up to 95 they still had R12. I went with the 99+ because it was readily available at the time.

93-94 was the first year of 134. I had a 94 and it was 134 and both my 95's are 134. Thank you for the info. I was just looking to try and increase performance a little bit.

 

[meir]

Sorry for reviving this old thread.
I'm putting a crate engine in the truck and thinking about replacing the AC compressor "while I'm in there", and would like to do it the right way.
the compressor I have now is obviously not the one that came with the truck.
the pressure switch on the compressor has two pins, but only one wire is coming from the engine wiring loom (gray wire).
this wire was disconnected for as long as I have the truck.
will appreciate any help with understanding the diagram in post#3.
if I understand correctly I will have to do the following:
1. eliminate the 1-wire connector with the gray wire as it is no longer in use.
2. get a new AC compressor pressure switch with 2 pins and a 2 wires pigtail.
3. cut the Lite Green wire from the pressure sensor located on the accumulator.
4. connect the 2 wires coming from the new compressor pressure sensor, in line with the light green wire (one wire to each side of the light green wire I just cut)
5. cut the Dark Green wire coming out from the accumulator switch and going to the AC compressor clutch, and install a relay (following the diagram).
if I got it right, then step 5 is optional, just to increase the signal going to the AC compressor clutch.

will appreciate it if one of the experts can confirm or correct the steps I'm about to take.
thanks in advance.

 

[PlayingWithTBI]

1. eliminate the 1-wire connector with the gray wire as it is no longer in use.

No, just ground that grey wire at the T-Stat housing. When it's grounded and you turn on the A/C, with the coldest setting, and fan speed set at 2 or 3, the recirculation door will open after 30 seconds to give you "Max Air".

2. get a new AC compressor pressure switch with 2 pins and a 2 wires pigtail.

Yes, I attached the link on post #3.

3. cut the Lite Green wire from the pressure sensor located on the accumulator.
4. connect the 2 wires coming from the new compressor pressure sensor, in line with the light green wire (one wire to each side of the light green wire I just cut)

Yes and yes.

5. cut the Dark Green wire coming out from the accumulator switch and going to the AC compressor clutch, and install a relay (following the diagram).

You don't need the relay unless you want to get full battery voltage to the compressor clutch. Just leave the Dk Grn wire alone until then.

if I got it right, then step 5 is optional, just to increase the signal going to the AC compressor clutch.

Yepper

Then you should remove the old compressor, orifice tube, accumulator, and condenser. You're gonna replace them all anyway. Make sure you get a Parallel flow condenser. Then flush the entire system. Check your new compressor to see if it shipped with PAG oil for R134a and how much. Take the correct additional amount of PAG oil, normally you need 8 oz total. Pour 1/2 in the compressor and 1/2 in the accumulator. Manually turn the compressor 3 or 4 revolutions to distribute the oil inside it. Then install the compressor, orifice tube, condenser, and accumulator, evacuate the system, check for leaks, and charge the system with the correct amount of R134a.

NOTE: This all is assuming you have an 88 or around there and don't have the "Max" air button on the Control Panel. YMMV

 

[meir]

This is awesome! thank you so much.
yes. my truck is 89 without the Max button on the AC.

 

[Schurkey]

Then you should remove the old compressor, orifice tube, accumulator, and condenser. You're gonna replace them all anyway. Make sure you get a Parallel flow condenser...

...and a 134a schrader valve conversion kit. If there's any refrigerant left in the system, I'd leak-test the system before having it discharged. Might as well find out if (where) the hoses/tubes, or evaporator are leaking.

Then flush the entire system.

Well, no. Flush all the parts you're going to re-use, and NEVER flush the receiver/dryer--accumulator, and compressor. The screen on the old orifice tube is your tell-tale for the amount of debris in the system.

There's no reason to flush new parts.

Check your new compressor to see if it shipped with PAG oil for R134a and how much. Take the correct additional amount of PAG oil, normally you need 8 oz total. Pour 1/2 in the compressor and 1/2 in the accumulator. Manually turn the compressor 3 or 4 revolutions to distribute the oil inside it. Then install the compressor, orifice tube, condenser, and accumulator,...

...replace EVERY O-ring in the system, recommended to lube the O-rings with Nylog Blue. I drop a quarter-ounce of fluorescent dye in the system...

www.amazon.com/Refrigeration-Technologies-RT201B-Gasket-Sealant/dp/B008HOSQQQ/ref=sr_1_2?crid=33OCL1BPFOCWS

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...evacuate the system,

Leave the system under vacuum for the longest practical time. I like to run the vacuum pump so as to achieve max vacuum during the hottest part of the day (if practical.) Water boils at ~75 degrees F when under strong vacuum, and you want the water to have enough time to vaporize and get pulled out. The hotter the day, the faster it boils off.

After sucking the system down long enough to get rid of any moisture, close the valves on the gauge set, shut off the vacuum pump, leave the system under vacuum overnight. The vacuum level on your gauge set should be the same the next morning if there's no leaks.

check for leaks, and charge the system with the correct amount of R134a.

Yup.

 

[meir]

Thanks for all the recommendations guys.
the AC was working fine before the old engine died.
it’s already converted to R134a, an I used REDTEK refrigerant with grate result. With that said, the truck was seating neglected for almost 4 years, as I was busy with my other projects. Most of the AC components were replaced shortly before the old engine past away, but I will replace some of the components mentioned above.
I have a friend that is an AC guy, who offered to help with the charging, even though I’ve done it successfully before. definitely all new O- rings and vacuum test. I already got the nylog blue in my tool box from other projects.
I was mostly confused with the 2 prong pressure switch and the 1 wire coming from the car.
PWT post cleared that confusion

 

[89bowtie]

Any R4 compressor will work, some are better than others - NAPA or AC DELCO are better but more expensive. I prefer new over reman. The 1-wire pressure switch is NLA you'll need to wire in the proper 2-wire switch in series with the low pressure cycling switch so you don't blow up the system when restarting on a hot day.

https://www.oreillyauto.com/detail/c/murray-climate-control/murray-climate-control-2-terminal-pressure-switch/mry0/35961/v/a/3384/automotive-truck-1988-chevrolet-k1500-pickup-4wd?q=A%2FC+high+pressure+switch&pos=3

Here's what I did on my 88 along with a relay for the clutch so I could get full battery voltage to it

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Edit: Check the air gap on the compressor before installing it - s/b 0.020" - 0.030". I had a new NAPA out of the box with >0.080". It smoked the clutch in about a week!

So connect the new two wires from compressor to the light green on the accumulator right?

 

[meir]

So connect the new two wires from compressor to the light green on the accumulator right?

Correct. Cut the light green wire and connect the two wires coming from the compressor switch, one to each end.

 

[351FUN]

This is good info, my compressor isn't being commanded to run but it's a similar situation, engine swap and carb with ecu removed. It's a 92 and has all the factory ac components replaced, I'm not sure how to verify the signal from the pressure switch without checking system pressure and I don't have the tools for that either. If it has leaked out already that's gonna be more fun stuff for the shop to chase down.