What to do with an inoperative R12 A/C system. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

morcey2 · 05-01-2009, 11:36 AM

I've got an 84

K1500, 305, 700R4 that has non-working A/C (R4 rotary compressor). This became very apparent yesterday when it was about 110 in the cab on a 65-degree day. The A/C hasn't been converted to 134A and it doesn't seem to currently have any refrigerant in it. Pushing in the valve on the low side gives a very slight hiss, but not what would be expected from an even semi-charged system.

I want to have a working A/C this summer, but I don't want to spend hundreds on it. (I may have to though.) I used to be EPA certified, but that was many moons ago. Doing a correct R134A retrofit will probably cost several hundred (new hoses, o-rings, accumulator, orifice tube, possibly compressor, and switches since the pressure will be different.

I'm going to get it pumped down and see if it will hold a vacuum. If it does, which I doubt it will, I'll probably just stick w/ R12. If it doesn't hold, that's where the real decision making will have to happen. It's hard to find a leak without some type of pressure in there to move things around. Doing a full R134A conversion before finding the leak could mean replacing the entire system anyway. (A 'Why didn't I notice that bullet hole in the condenser before?' moment.)

Anyone have any leak-finding tricks that might help here? I'm already assuming I'm going to have to drop at least $200 on this, but I don't want to. At least with an empty system, I don't have to pay someone else to recover the old refrigerant.

Matt

Restrorob · 05-01-2009, 12:15 PM

Matt,

There are dyes you can purchase in a can and add it to the system just like refrigerant, If there is a leak outside of the evaporator box it will glow a florecent color.

I have a leak in my 97 and will be adding a can soon as I finish a couple other things.....

454HO · 05-01-2009, 01:46 PM

Nitrogen is an inert gas and is often used to pressurize a system for leak detection. If you can find a filling station that has compressed nitrogen for tires, and it is at least 99% pure, then you can try using that. Perhaps get one of those portable air tanks, purge it a few times, then use it to pressurize your a/c system. Then do the soap and water trick and check for bubbles.

morcey2 · 05-01-2009, 02:30 PM

Ever have one of those

moments?

Right after I got the truck, I disconnected the idle speed-up solenoid because the engine was idling at 1300 when put it on defrost. The fact that it's getting power means that the AC clutch is getting power. The fact that the AC clutch is getting power means that the pressure switch on the accumulator is registering enough pressure to close. That means that there's got to be some pressure in the system. That also probably means that the AC clutch is shot. (maybe).

That or my brain is shot from it being friday afternoon on a very long week.

Could be both.

Matt

05-01-2009, 11:36 AM	#1
morcey2 Registered User Join Date: Mar 2009 Location: Central utah, UT Posts: 105	What to do with an inoperative R12 A/C system. I've got an 84 K1500, 305, 700R4 that has non-working A/C (R4 rotary compressor). This became very apparent yesterday when it was about 110 in the cab on a 65-degree day. The A/C hasn't been converted to 134A and it doesn't seem to currently have any refrigerant in it. Pushing in the valve on the low side gives a very slight hiss, but not what would be expected from an even semi-charged system. I want to have a working A/C this summer, but I don't want to spend hundreds on it. (I may have to though.) I used to be EPA certified, but that was many moons ago. Doing a correct R134A retrofit will probably cost several hundred (new hoses, o-rings, accumulator, orifice tube, possibly compressor, and switches since the pressure will be different. I'm going to get it pumped down and see if it will hold a vacuum. If it does, which I doubt it will, I'll probably just stick w/ R12. If it doesn't hold, that's where the real decision making will have to happen. It's hard to find a leak without some type of pressure in there to move things around. Doing a full R134A conversion before finding the leak could mean replacing the entire system anyway. (A 'Why didn't I notice that bullet hole in the condenser before?' moment.) Anyone have any leak-finding tricks that might help here? I'm already assuming I'm going to have to drop at least $200 on this, but I don't want to. At least with an empty system, I don't have to pay someone else to recover the old refrigerant. Matt

05-01-2009, 12:15 PM	#2
Restrorob The One And Only !!! Join Date: Jan 2007 Location: Hole in the woods Florida Posts: 4,567	Re: What to do with an inoperative R12 A/C system. Matt, There are dyes you can purchase in a can and add it to the system just like refrigerant, If there is a leak outside of the evaporator box it will glow a florecent color. I have a leak in my 97 and will be adding a can soon as I finish a couple other things..... __________________ 93 Jeep XJ 88 Buick La Sabra Toys; 88 TA-GTA in the works.... 97 GMC Ext. Cab 502 Crate 5 Spd......Sucks Gas But Haulz Azz ! The primary function of an Engineer is to make it difficult for the Fabricator and impossible for the Mechanic. *"Why go out preserved when you can go out beat up, worn out, sliding in sideways screaming, Holy Sh!t What A Ride" !!!*

05-01-2009, 01:46 PM	#3
454HO Registered User Join Date: Apr 2005 Location: Austin, TX Posts: 1,224	Re: What to do with an inoperative R12 A/C system. Nitrogen is an inert gas and is often used to pressurize a system for leak detection. If you can find a filling station that has compressed nitrogen for tires, and it is at least 99% pure, then you can try using that. Perhaps get one of those portable air tanks, purge it a few times, then use it to pressurize your a/c system. Then do the soap and water trick and check for bubbles. __________________ - Greg

05-01-2009, 02:30 PM	#4
morcey2 Registered User Join Date: Mar 2009 Location: Central utah, UT Posts: 105	Re: What to do with an inoperative R12 A/C system. Ever have one of those moments? Right after I got the truck, I disconnected the idle speed-up solenoid because the engine was idling at 1300 when put it on defrost. The fact that it's getting power means that the AC clutch is getting power. The fact that the AC clutch is getting power means that the pressure switch on the accumulator is registering enough pressure to close. That means that there's got to be some pressure in the system. That also probably means that the AC clutch is shot. (maybe). That or my brain is shot from it being friday afternoon on a very long week. Could be both. Matt Last edited by morcey2; 05-01-2009 at 02:30 PM.



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