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

[PlayingWithTBI]

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.

HELLO!
Here's the HP switch that goes on the back of the R4 compressor. It comes on when pressure is <200 and shuts off >430 PSI.

https://www.oreillyauto.com/detail/c/murray-climate-control/air-conditioning---heating/air-conditioning-switches/a-c-high-side-pressure-switch/ca1e596f8ca1/murray-climate-control-2-terminal-pressure-switch/mry0/35961/v/a/3009/automotive-truck-1988-chevrolet-c1500-pickup-rwd?q=a%2Fc+pressure+switch&pos=0

Here's a diagram I drew up for the HP switch in series with the LP Cycling switch and an auxiliary relay to give you full battery voltage to the clutch (all in blue). I was only getting a little over 11V at the coil, with the relay I now get over 14V

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Another word to the wise, check the free air gap on the clutch itself. I had a new NAPA compressor smoke the clutch due to a gap >0.080" when it s/b closer to 0.020" - 0.030"

 

[PlayingWithTBI]

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

I looked at that fan on RA, they show it only fits 1997-1999 C1500 trucks (among others), no TBIs. Is there a reason for that?

 

[1998_K1500_Sub]

an auxiliary relay (will) give you full battery voltage to the clutch (all in blue). I was only getting a little over 11V at the coil, with the relay I now get over 14V

@PlayingWithTBI, that's an interesting addition which I hadn't noticed when you posted this information in a prior thread.

I like it because it allows the switches to NOT carry the clutch current and, instead, carry the much smaller current required to simply operate the "auxiliary relay" you've added.

 

[PlayingWithTBI]

I like it because it allows the switches to NOT carry the clutch current and, instead, carry the much smaller current required to simply operate the "auxiliary relay" you've added.

Yeah, kinda the same theory as the "4 High" mod.

 

[L31MaxExpress]

I looked at that fan on RA, they show it only fits 1997-1999 C1500 trucks (among others), no TBIs. Is there a reason for that?

Because GM never had that fan until the 97s came out. All their listings are based on interchanges.

 

[PlayingWithTBI]

Because GM never had that fan until the 97s came out. All their listings are based on interchanges.

Well, I pulled the trigger on it, $56.06 total with our $2.04 5% discount, whoopie! If it helps on my truck, I'm sure it'll help most others

I had to tell them it was for a 1998 instead of my 1988 to

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I loathe, abhor, detest, despise, abominate, shipping charges

 

[tayto]

I looked at that fan on RA, they show it only fits 1997-1999 C1500 trucks (among others), no TBIs. Is there a reason for that?

I put this fan on a friends 92 GMC C2500. works fine, no clearance issues. Used a severe duty hayden clutch, there was one individual on this forum thay claimed it sounded like a 747 taking off. I found the complete opposite, it was quieter than the steel fan and ran less at cold start up. I liked it so much that I bought one for my squarebody as I am currently doing a B/F-body serpentine swap.

 

[Donald Mitchell]

If it fits the stock clutch, i want one.

 

[Donald Mitchell]

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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This is the **** I always get into. My truck was converted years ago, so I'm thinking everything you buy now is already set for R134a. Just bought a new AC delco clutch cycle switch and I guess it won't work? I also just noticed the acumulator has an R12 sticker with it, not on the can. Well, I never get in a hurry so it can wait.

 

[1998_K1500_Sub]

I also just noticed the acumulator has an R12 sticker with it, not on the can. Well, I never get in a hurry so it can wait.

I believe the accumulator (receiver / dryer) for your year's "R12" system has different thread pitch on the fittings than those on a later "R134a" accumulator (e.g., which might be used on a 1995 truck). At least, this is a problem I had on a 1995 S10 I was working on recently... an earlier "R12" accumulator looked like it would fit, but the threads would not play well together with those on the OE R134a evaporator.

Ditto with switches, which is why @L31MaxExpress mentioned the "find" of a cycling switch appropriate for R134a that had the proper fitting for an "R12 vintage" accumulator.

I believe you can use an "R12" accumulator with R134a/PAG in the system, so that cause is not lost AFAIK.

I'm treading into new territory here, but... My belief is, if you bought new parts for your particular vehicle year, you'll be OK. If you tried to mix and match, e.g., a later R134a-vintage receiver / dryer and perhaps a hose assembly (e.g., from a 1995 truck, which seems intuitive) , with some existing R12-vintage parts already on your truck (e.g., evaporator), the fittings may not join. Similarly, if you were to replace ALL the R12-vintage parts with those from a R134a-vintage year (1995), I expect they will fit and work fine. I have not proven this.

If you haven't checked your fittings to make sure everything's going to mate, you might do that ASAP.


(finally, some misc thoughts on R12 follow, feel free to ignore)

For the record, there are replacement refrigerants for stationary applications which originally used R12, e.g., grocery store stand-alone chillers, U-Line ice makers or SubZero refrigerators made prior to ~1994 to name only a few. R406a is one such replacement, composed of a mixture of gases (three, I think). While there are reasons for not using R406a as an R12 replacement in older autos (e.g., leakage, a common problem in such systems, causes fractioning of component gases from the refrigerant and so changes its properties), there are people who do use R406a in their vehicles as an R12 replacement. Google it. R406a traces its roots to a professor at Purdue who, around 1990, dabbled in refrigerants, outside of his field of specialty (PhD EE). This is, at least, as I remember it. A friend of mine was one of his students.