1990 K1500 a/c repair

[R422b]

Don't put pag oil on fittings and orings use mineral oil it doesnt draw moisture like pag. Using pag oil on threads will cause thread corrosion and seize them.Pag oil should be used in the system just not at fittings.

This is a far superior thread lubricant and it is also good for o-rings and other refrigerant fittings. I put a dab on my 134a couplers before connecting because it helps seal better.

https://www.trutechtools.com/RT201B...i79GJOoFmmjQgz5SbsLmP7bU7aEUU3g8aAqIQEALw_wcB

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[R422b]

Y


Your comment about using the Ford orifice tube got me thinking. Would R12 and R134a use a different tube? I know R134 molecules are smaller that’s why the systems are more prone to leaks than R12, plus they run at higher pressure.

I believe when you convert refrigerant you should use the orifice that matches the compressor and of course preferably one that has the right rubber seals for the refrigerant. If it uses an expansion valve you will have to use the correct one for the refrigerant.
That is my opinion based on my refrigeration knowledge. I am not an auto ac mechanic though so keep that in mind.

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[Frank Enstein]

I know the pressures are different but I don't know beyond that. Sorry. The info is from 15-20 years ago.

 

[studigggs]

I bought a 1990 K1500 with a frozen a/c compressor. The previous owner routed a shorter belt around the a/c compressor and it appear to have been this way for quite some time as the a/c pulley has developed some rust on it. The compressor looks original to the truck and I can barely turn it it by hand.

I have not done a lot of a/c work in the past (replaced a compressor once but it was on a newer vehicle that already had r134a). What I’m trying to do is figure out what parts I need to buy to get the a/c running again and converted to r134a. So far:

Compressor: GM brand, 1520185

Drier/accumulator: GM brand, 151676

Orifice tube: There appears to be several variations of this part, which one do I need?

Lines: Do I need new a/c lines?

Condenser: Do I need a new condenser?


Oil, Flush, adapters, o-rings?

Hoping to find someone that has done this before to help me get a parts list together.

My advice would be to replace everything save for the evaporator. New lines, accumulator, compressor, condenser, O-tube etc. I had a hard time getting the Four Seasons and UAC compressor manifold o-rings to work, so I did splurge on an AC Delco set which solved the problem. Assuming its still R12, you will need a new high pressure switch on the back of your compressor so that your fresh/recirc door works properly and a new low pressure switch on your accumulator that is calibrated for R134 pressures. I do have a parts list in my post history as well as some horror stories with the R4 compressors. I ended up using the UAC scroll compressor and its been going strong 2 years now. I could never get an R4 past a desert heat soak without blowing the case seal, but if you are in a moderate climate, the standard R4 piston compressor may work for you.

 

[idlook2]

Dumb question, is is possible to have the system re-filled with R12 after replacing the parts or does it have to be converted to R134a?

 

[R422b]

Dumb question, is is possible to have the system re-filled with R12 after replacing the parts or does it have to be converted to R134a?

Of course but unless you do it yourself it might be hard to find someone to do it.

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[Steven Petersen]

Dumb question, is is possible to have the system re-filled with R12 after replacing the parts or does it have to be converted to R134a?

I refilled mine with R12. I have a 30 pound jug I’m using. I still see them around occasionally.

 

[Schurkey]

The FIRST thing you need to do is to figure out if the COMPRESSOR is seized, or if the PULLEY BEARING is seized.

Given that the guy re-routed the belt, my money is on the pulley bearing. Maybe all you need is a bearing, fresh O-rings, desiccant, and an orifice tube. Vacuum and recharge.

Maybe you still want an entire compressor assembly installed anyway, along with condenser, hoses, switches, and all the rest. Some of this depends on your choice of refrigerant.

 

[Steven Petersen]

The FIRST thing you need to do is to figure out if the COMPRESSOR is seized, or if the PULLEY BEARING is seized.

Given that the guy re-routed the belt, my money is on the pulley bearing. Maybe all you need is a bearing, fresh O-rings, desiccant, and an orifice tube. Vacuum and recharge.

Maybe you still want an entire compressor assembly installed anyway, along with condenser, hoses, switches, and all the rest. Some of this depends on your choice of refrigerant.

I agree the compressor should not be written off yet. One thing to look for is if has the oily mess where the 2 halves come together. Mine did, and my sniffer also confirmed the leak coming from there so I replaced it.

I highly recommend keeping it on R12. It is a superior cooling product and your 1990 system was designed to run on it. I checked out Ebay and there are several individual bottles of R12 available. If you make sure your system is tight, a charge can last you a decade or longer.

 

[PlayingWithTBI]

you will need a new high pressure switch on the back of your compressor so that your fresh/recirc door works properly

This all depends what year your truck is and does it have the "max" air button. 88 - 90 (I think) didn't have that button, they will open the recirc door after 30 seconds when the fan is on 2 or 3 and the temp is set to its coldest setting (with A/C on of course). The OE pressure switch on the back was used to close that door but, there wasn't a high pressure shut off switch in those years so, when hot, and shut off for a few minutes, you restart the engine you will get a high pressure spike. This blew out that HP switch on mine - sounded like a shot gun going off. I wound up taking a HP switch, in a new compressor (since the groove was damaged when the previous one blew out) and wired it in series with the LP switch so now, when pressures go over 430 it will shut off the compressor. I did a write up on this a year or 2 ago. Here's the schematic I drew up for that and a relay giving me full battery voltage to the clutch coil. What I added is labelled in blue.

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