New A/C system, Oil amounts in components. 1990 Silverado 5.7L R4

[Donald Mitchell]

I am ready to put the system together and have it charged. Everything is new and mostly AC Delco. I would like to know where the oil goes and the amounts for each component, Compressor, accumulator, evaproator, and condenser. I will dump the compressor to make sure it has oil and refill. I read that PAG 150 is the correct oil. Also what to lube the O-rings with? I am reusing the original lines and flushing them. Any other thngs i need to know would b helpful. I'm really looking forward to having A/C again.

 

[98chevy2500SS]

I always lube up o-rings with PAG oil. Since you have the R4 compressor, the entire system takes 8 oz. of PAG oil. I'm not entirely sure how much goes in each component, as I usually take my trucks to a repair shop after I get done replacing my A/C systems so they can use their fancy A/C machine that will dispense correct amounts of oil and refrigerant.

 

[L31MaxExpress]

I am ready to put the system together and have it charged. Everything is new and mostly AC Delco. I would like to know where the oil goes and the amounts for each component, Compressor, accumulator, evaproator, and condenser. I will dump the compressor to make sure it has oil and refill. I read that PAG 150 is the correct oil. Also what to lube the O-rings with? I am reusing the original lines and flushing them. Any other thngs i need to know would b helpful. I'm really looking forward to having A/C again.

What I have always done, half into the compressor, the rest can be divided between the accumulator and condenser. That being said, charge some R134a into it, then spin the compressor over 10-15x with a clutch spanner to make sure you do not hydraulic lock the compressor on oil.

That being said, when I did my Sanden SD7H15 they said precharge the compressor with up to 10oz of oil. I used Sandens formula and also looked at GMs specs for my Express van. The dash air only GM was 48oz R134a and 8 oz PAG oil, rear air was 78oz R134a and 11oz PAG. My system is 68oz. Using Sandens formula I came up with 9.97 oz. Looking at the system, figure the reciever dryer and compressor hold some oil as does the condenser. The difference is the added rear lines and evaporator. For a sanity check, looked like 1oz PAG per 10oz R134a for the rear unit on GM. Reducing it by that ratio for my 68oz I came up with 10oz. 9.97 vs 10oz. I put 10oz into the compressor, charged a can of refrigerant into it and spun over the clutch 10-15x. Fired it up, charged the rest of the refrigerant and it has been ice cold since and the compressor is very quiet.

 

[L31MaxExpress]

If you have a R4, PAG 150 is correct. I like the one that has Ice32 additive. On my latest Sanden they say to use SP-15 which is 100 viscosity. They recomeended only their oil, since I had the system open for some time, I flushed the whole system until just clear flushing chemical came out and then pulled it into a near 30 in/hg vacuum for 1 hour. Let it sit for 2 hours and the vacuum had held. My SD7H15 was precharged with 135cc or 4.565oz oil in it according to Sanden, the amount I added was equivalent to 160cc and I used a medicine syringe to add the oil. I like CC rather than OZ and it is easy to convert using an online calculator. CC is easy to measure with a cheap drug store syringe.

I hope your condenser is a modern parallel flow upgrade, they work really well.

I also like the Ford Red 0.062" orifice tube. It has better idle and slow speed performance than the GM white 0.072 with R134a as it lets the low pressure drop a little more and lowers the boiling point. I use them in conjunction with an adjustable cycling switch and a high side high pressure cut-off.

I also like a 14-16" pusher fan in front of the condenser. On my older retrofits, I use a trinary switch on the high side. I use the trinary switch to engage the pusher fan and wiring the clutch through it shuts the compressor off for excessively low or high pressure helping prevent compressor failure. When you are going down the highway with adequate airflow the trinary switch will open the pusher fan circuit, saving the power draw on the alternator and thus engine and increase the life of the fan motor.

 

[L31MaxExpress]

Should have gone into detail on the cycling switch. The factory is not adjustable on the GMT400. A R12 year system has a dryer with a different fitting than the R134a. You cannot put a R134a switch on a R12 system dryer. The R134a low pressure cutout aka cycling switch has a lower pressure set point than the R134a one. A few PSI makes a big difference in cooling while driving. With the R12 dryer, grab a low pressure switch for a 1990 G20 van. It is adjustable. Four season 36674 or equivalent and the matching connector Four Seasons 37219. Splice the new connector in place of your stock one, wire orientation does not matter. Install the switch on the accumulator. Adjust the adjustment screw between the terminals of the R12 switch 1/4 turn CCW. If the evaporator does not freeze up, reducing airflow, keep adjusting the pressure 1/8 turn CCW and retest. You can get the vent temps well into the 30s on the highway, just make sure you don't go below 15-20 PSI on the low side when the engine is reved up as the compressor needs some pressure in the low-side for adequate oil return and you do not want a pinhole leak somehwere pulling air and thus moisture into the system if it were to drop into a vacuum.

The 36674 switch is preset for 25 psi. 1/4 turn will decrease the cutoff pressure about 3-4 psi to 21 psi. 25 psi puts the boiling point of the R134a at 29°F but with air flowing across the evaporator the surface will still be above freezing. 21 psi puts the boiling point down around 26°F. I can run my vent temps at about 33°F steady without worrying about evaporator freeze up. If it does start to freeze up, usually 1/8 turn CW will fix the situation if you test with slow changes.

I used a R134a threaded version of that same switch for a 94 G20 Van on my 97 Express and 99 Tahoe with that stupid factory small failure prone non adjustable switch. Small adjustment to that switch dropped my Tahoe from 42°F to 33°F going down the road at the center vents.

 

[L31MaxExpress]

I actually just stumbled across a switch made correctly for R134a that is a direct replacement for the R12 switch. The R12 switch opens at 30 psi. The R134a switch opens at 20 psi. At 30 psi R134a is boiling at 35°F. Vent temps are usually 6-10°F higher. No wonder some of these retrofits are hard pressed to cool well. I was not aware they were making these until today. Even so, I still prefer having an adjustable switch that I can dial in to get the most out of the system. Hopefully this post helps some early R134a retrofited GMT400 guys with subpar cooling.

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[1998_K1500_Sub]

I am ready to put the system together and have it charged. Everything is new and mostly AC Delco. I would like to know where the oil goes and the amounts for each component, Compressor, accumulator, evaproator, and condenser. I will dump the compressor to make sure it has oil and refill. I read that PAG 150 is the correct oil.

Put half the oil (4oz) in the receiver /dryer, the other half (4oz) in the compressor. Keep in mind the compressor, if it had oil in it already, will have ~1/2oz of residual remaining in it after draining, so adjust accordingly.

Also what to lube the O-rings with?

Use Nylog Blue on the O-rings and as an assembly lube on the fittings.

@L31MaxExpress gave you a lead on a cycling clutch switch (good find!).

If your system doesn't have a high-pressure cut-out switch, you should add one b/c of the higher pressures inherent to R134a systems. I think @PlayingWithTBI posted a part number for this switch earlier this summer. Hopefully he'll chime-in here.

There was also discussion about how to wire the cycling and high-pressure cut-out switches (it's simple, but instructions help) in one of the recent threads. I'll try to find it.

I may add more later.

It's an easy job, but there are a lot of details... from the (re)assembly all the way though charging and initial-start up.

 

[L31MaxExpress]

One other thing. To keep the high side aka head pressure in check and prolong the life of the compressor, R134a needs more airflow for the condenser. While everything is apart it would be a great time to put a new fan clutch on it and upgrade from that 5 bladed fan. The 11 bladed tow package fan will bolt right onto a TBI clutch and its 11 blades have more surface area to pull more airflow. Might not even need a pusher fan for good results with the 11 bladed fan. It gets very hot here in north Texas during summer and I have done alot of experimentation to get better a/c output.

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[1998_K1500_Sub]

@L31MaxExpress' earlier comments cover some good ground.

Here's a REAL long thread on an AC rebuild from earlier this year. It's a LONG read, but has nuggets of info in it. It's shortcoming is it's focused on an existing R134a system, so it doesn't cover the issues of a retrofit, but it covers other matters, e.g., related to (re)assembly, evacuating and charging.

1996 C1500 Reg Cab AC not working - what all do I need?

Hi, I have a 1996 C1500 4.3 reg cab 8ft bed and the A/C is not working, just blows ambient air. Is there anything simple I might be able to check to see if the system is salvagable? I was thinking if the system is bad, to maybe buy a kit or the individual parts needed to replace and flush...

www.gmt400.com

 

[L31MaxExpress]

Put half the oil (4oz) in the receiver /dryer, the other half (4oz) in the compressor. Keep in mind the compressor, if it had oil in it already, will have ~1/2oz of residual remaining in it after draining, so adjust accordingly.



Use Nylog Blue on the O-rings and as an assembly lube on the fittings.

@L31MaxExpress gave you a lead on a cycling clutch switch (good find!).

If your system doesn't have a high-pressure cut-out switch, you should add one b/c of the higher pressures inherent to R134a systems. I think @PlayingWithTBI posted a part number for this switch earlier this summer. Hopefully he'll chime-in here.

There was also discussion about how to wire the cycling and high-pressure cut-out switches (it's simple, but instructions help) in one of the recent threads. I'll try to find it.

I may add more later.

It's an easy job, but there are a lot of details... from the (re)assembly all the way though charging and initial-start up.

Yep the switches need to be in series or inline with each other so that either one opens the circuit. The trinary switch I use comes as a T with a R12 thread on one side, the 1/4" switch port and the R134a high side service port on the other. Pull the shrader core from the R12 service port, thread the assembly on. I generally wire the trinary switch on the power side of the cycling switch so that once the fan is on it stays on despite the low pressure cutout switch cutting the compressor for the low side cutoff. Its easier on the compressor when it cycles back on to have lower high side pressure from the fan staying on.