92-99 K1500 Suburban - A/C System Part Number Evolution

[Wildblue19]

I've been fighting for a few years with my R134 performance following a conversion from R12 (separate thread here outlining that process). Vehicle is a 5.7L 1993 K1500 Suburban and the A/C sucks.

I wanted to know how GM developed the dual-air (C69) system on these trucks throughout the years, wondering what parts were changed (if any) during the swap from R12 to R134.

Table below is what I found (Part numbers drawn from GM databases online):

	1992​	1993​	1994​	1995​	1996​	1997​	1998​	1999​
Refrigerant / Fittings	R12, SAE	R12, SAE	R134, Metric (?)	R134, Metric	R134, Metric​	R134, Metric​	R134, Metric​	R134, Metric​
Condenser	52411109 (88-93), 52486531 (92-93)	52411109 (88-93), 52486531 (92-93)	52458719 (94-95)	52458719 (94-95)	52480034 (96-00)	52480034 (96-00)	52480034 (96-00)	52480034 (96-00)
Compressor	88964864 (84-92)	88964862 (93-95)	88964862 (93-95)	88964862 (93-95)	89019367 (96-02)	89019367 (96-02)	89019367 (96-02)	89019367 (96-02)
Evaporator (F)	52456123 (91-93)	52456123 (91-93)	52464036 (94-02)	52464036 (94-02)	52464036 (94-02)	52464036 (94-02)	52464036 (94-02)	52464036 (94-02)
Orifice Tube (96+ non rear A/C got yellow 0.62)	Black (.072)	Black (.072)	Black (.072)	Black (.072)	Black (.072)	Black (.072)	Black (.072)	Black (.072)
Evaporator (R)	52457491 (92-93)	52457491 (92-93)	52481081 (94-99)	52481081 (94-99)	52481081 (94-99)	52481081 (94-99)	52481081 (94-99)	52481081 (94-99)
TXV (Straight type only)	52460953 (92), 52460954 (92-93)	52460954 (92-93)	52406098(94-99), 52413202(94-95)	52406098(94-99), 52413202(94-95)	52406098 (96-99)	52406098 (96-99)	52406098 (96-99)	52406098 (96-99)
Accumulator (RPO specific, ex. 2724691 is not for C69)	2724690 (92-93)	2724690 (92-93)	1132816 (94-95)	1132816 (94-95)	2724962 (95-00)	2724962 (95-00)	2724962 (95-00)	2724962 (95-00)

To my surprise, there is a ton of variability in the parts. 94-95 trucks saw a lot of short-lived changes, and post 96 things seem to stabilize.

I am posting this for information to help others, since I haven't made my mind up on what parts (if any) I would want to swap to on my truck to try and improve R134's performance, but will update as that changes. My biggest question for now is if changing my rear R12 TXV to a 134 one would help but... that necessitates a total swap of all lines to match the metric threads.

 

[Schurkey]

How about the low-pressure cutout switch?

I learned (from another post on this site, recently) that the R12 switch opens at a higher pressure than the R134a switch. IF the pressure in the evaporator is lowered, the temperature should also lower.

So it would be really wonderful if the low pressure switch fittings were the same so that an R134a switch could thread onto an R12-style accumulator for those of us contemplating conversions.

 

[MIHELA]

I believe the only difference in accumulator between 94-95 and 96-99 is a change in the angle of the fittings. I'm curious what the difference in condenser is, don't they have a different switch?

 

[Wildblue19]

How about the low-pressure cutout switch?

Low pressure cutout on GM shows 88-93 as 52457853 for R12, and (interestingly) listed as 1988-2002 R134 is 52465555.

 

[Wildblue19]

I believe the only difference in accumulator between 94-95 and 96-99 is a change in the angle of the fittings. I'm curious what the difference in condenser is, don't they have a different switch?

Accumulator fitting angle idea appears to be correct, the external otherwise looks the same.

For condensers: 88-93 has no high pressure switch fittings. 94+ have a port for the pressure switch, and otherwise they look the same so it's probably a fitting size difference across the years. I read on another forum that 94 and up the fittings went to metric, but a guy on here has a 1990 with a condenser that has a high side port on it (indicating 94+ model) and it's all bolted together so I'm not sure on the fittings.

 

[GoToGuy]

Condenser or compressor?

 

[L31MaxExpress]

How about the low-pressure cutout switch?

I learned (from another post on this site, recently) that the R12 switch opens at a higher pressure than the R134a switch. IF the pressure in the evaporator is lowered, the temperature should also lower.

So it would be really wonderful if the low pressure switch fittings were the same so that an R134a switch could thread onto an R12-style accumulator for those of us contemplating conversions.

Four Seasons makes a R134a specific switch for the R12 threaded dryer. That being said I use a 93-95 G20 van R134a switch in the R134a trucks. It is the older style with the adjustment screw between the terminals. I can adjust the pressure cut-off to a point that prevents freezing the evaporator but allows the compressor to cycle just short of doing so. In practice I adjust it to a point where the evaporator freezes up, then back off a small amount until it no longer freezes up. It picks up some frost, but the reduced heat transfer forces the system to cycle and instantly melts the frost.

 

[Wildblue19]

Condenser or compressor?

Condenser.

94+:

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93 and below:

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[Wildblue19]

Four Seasons makes a R134a specific switch for the R12 threaded dryer.

Do you have a part number? I found something like that here but couldn't find it for a G20.

 

[Schurkey]

Four Seasons makes a R134a specific switch for the R12 threaded dryer. That being said I use a 93-95 G20 van R134a switch in the R134a trucks. It is the older style with the adjustment screw between the terminals. I can adjust the pressure...

This one? Murray 36496? One of the several photos shows a screw between the terminals. Has Fitting Thread Size: M12-1.50 which may not be right for R12 vehicles.
www.oreillyauto.com/detail/c/murray-climate-control/murray-climate-control-2-terminal-pressure-switch/mry0/36496/v/a/3310/automotive-van-1994-chevrolet-g20?q=Low+pressure+switch&pos=1

https://www.oreillyauto.com/detail/c/murray-climate-control/murray-climate-control-2-terminal-pressure-switch/mry0/36496/v/a/3310/automotive-van-1994-chevrolet-g20?q=Low+pressure+switch&pos=1

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[LATER EDIT]

Murray 36674. This one fits R12 systems with a 7/16-20 thread, and also has the screw between the terminals. Suitable for R134a pressures.
www.oreillyauto.com/detail/c/murray-climate-control/murray-climate-control-2-terminal-pressure-switch/mry0/36674/v/a/3384/automotive-truck-1988-chevrolet-k1500-pickup-4wd?q=Low+pressure+switch&pos=0

https://www.oreillyauto.com/detail/c/murray-climate-control/murray-climate-control-2-terminal-pressure-switch/mry0/36674/v/a/3384/automotive-truck-1988-chevrolet-k1500-pickup-4wd?q=Low+pressure+switch&pos=0