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R12 to R134 conversion

tRustyK5

tRustyK5

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What gets changed to run the newer 134 stuff. I want to get the AC on the Blazer working again...system looks complete, everything is plugged in, no lines undone but it doesn't work so I'm assuming it lost it's charge at some point. Being a 90 I'm pretty sure it was an R12 system from the factory right?

Is the conversion something that can be done at home, or better off to (gasp) take it to a shop to have done?

If it's best to take it in is it expensive assuming nothing major is wrong with the system?

School me on AC please.

Rene
 
most autoparts stores sell the conversion kit. its 2 adapters for the existing R-12 parts, and they screw on top of them so you can hook the hose adapter to them that comes in the kit. then its a matter of putting the cans of refidgerant and the 1 can of oil into the system. this is the Basic way of doing it.

BUT

seeing i do heating and cooling for a living i would "myself" hook up my vacuum pump to the system first, before i install any 134 into it.. and make sure there isnt any leaks in the system. seeing it was a R-12 truck unless someone unhooked something on the A/C it still should have refridgerant in the system unless it leaked out somewhere. most likely it leaked out of the O-rings on the hoses, or at the dip tube in the system, or possibly a shraeder valve. but not likely. i use nitrogen to pressurize the system and check for leaks after that. and then repair the system, and check again!! you can't be to carefull here!!! once i have verified i don't have any leaks i hook my vacuum pump up again and pull any left over nitrogen/refridgerant out of the system. and then charge it up with the conversion kit, which you want to make sure you install a kit that has OIL!!!!! otherwise your compressor life will be shortened! the kits they sell for this are pretty cheesey at best but do work. i still rely on my 134a manifold gauges and a 25lb cylinder.. but those arent required to do the job.


on the other hand if you take it to someone and they do the convert you should get a warranty out of it, in case 2 weeks down the road you end up turning it on, and get no cooling. you can take it back, and its there problem not yours! just a thought

hope this helps

Ck1500
 
you should change all the o rings and seals, oriface tube/expansion valve, dryer, and drain the compressor to get the oil out, you should also flush the lines, evap and cond. put correct oil in system and vacuum it down to -30in, see if it holds a vac for atleast 15 mins, if it doesnt then you have a leak and need to find it. if it holds vacuum it down for atleast 30 more mins to get all the old freon and moisture out. then fill it with 80% of r134 as you would r12. but without gauges you cannot diagnos some problems if it doesnt work after all that. if a system is left open for a long time 1yr plus i repalce the evap, cond, and comp just to make sure.

sorry for the terrible spelling
 
proliane cooling and heat i believe is making the true multiple path condensers for our trucks now (81-87), would nicely compliment the r134a conversion and make it alot colder over the old r12 single path flow. I plan to install one whenever i get around to doing my ac, i have everything else.
 
I have headers on my truck and had to remove the compressor do to not having a bracket. Do they make brackets for use with full length headers?
 
Since this thread is newer i gues i will ask this. What does it take to purge/clean out a system?
 
Ck1500 said:
most autoparts stores sell the conversion kit. its 2 adapters for the existing R-12 parts, and they screw on top of them so you can hook the hose adapter to them that comes in the kit. then its a matter of putting the cans of refidgerant and the 1 can of oil into the system. this is the Basic way of doing it.

BUT

seeing i do heating and cooling for a living i would "myself" hook up my vacuum pump to the system first, before i install any 134 into it.. and make sure there isnt any leaks in the system. seeing it was a R-12 truck unless someone unhooked something on the A/C it still should have refridgerant in the system unless it leaked out somewhere. most likely it leaked out of the O-rings on the hoses, or at the dip tube in the system, or possibly a shraeder valve. but not likely. i use nitrogen to pressurize the system and check for leaks after that. and then repair the system, and check again!! you can't be to carefull here!!! once i have verified i don't have any leaks i hook my vacuum pump up again and pull any left over nitrogen/refridgerant out of the system. and then charge it up with the conversion kit, which you want to make sure you install a kit that has OIL!!!!! otherwise your compressor life will be shortened! the kits they sell for this are pretty cheesey at best but do work. i still rely on my 134a manifold gauges and a 25lb cylinder.. but those arent required to do the job.


on the other hand if you take it to someone and they do the convert you should get a warranty out of it, in case 2 weeks down the road you end up turning it on, and get no cooling. you can take it back, and its there problem not yours! just a thought

hope this helps

Ck1500
Click to expand...

Great advise!
 
OK, so my BIL had given me a recharge kit he used on his '97. Has a gauge and an adaptor for the low side. I expected no pressure, but found ~45 psi on the low side, and quickly disconnected it as I was of course venting R12. :doah: Only for a second or two.

So, I still have R12 in the system. When I turn the controls to AC the computer bumps the idle from ~700 to ~950 or so...but the clutch doesn't engage at the compressor. I can turn the compressor by hand (the front part of the clutch set-up)

so, possible the clutch is bad? there is a plug on the top with two wires...anyone know which one of the wires should have power to engage the clutch?

No sense swapping to 134a if my system still holds the R12 fine right?

Rene
 
Does the clutch try to engage at all? I would put a jumper in the low pressure switch and see if the clutch will engage. You can do this without the engine running. Listen for the click.
Static pressure, engine not running, should be around 135psi.
Switching to 134-A? If you have a small leak that requires a recharge every year or so can be expensive. Going price for R-12 in shops around here is $85 a can. 134A- $6.50 at Wally World.
 
OK, assume I'm AC stupid...

Where is the low pressure switch and how do I jump it?

Rene
 
tRustyK5 said:
OK, assume I'm AC stupid...

Where is the low pressure switch and how do I jump it?

Rene
Click to expand...

Just finished doing it...went out and snapped a few photos for you just now.

small_DSC08619.JPG


small_DSC08620.JPG


small_DSC08621.JPG


small_DSC08622.JPG
 
OK thanks.

I just went out and wiggled the plug at the compressor, and got a click. Started it up, AC on MAX and the clutch engages for about 1.5 seconds, disconnects for 2 seconds and repeats. Vent temps are still warm. I'm assuming it's right on the edge on minimum pressure, but not enough R12 to actually cool anything?

Rene
 
ScottMH said:
you should change all the o rings and seals, oriface tube/expansion valve, dryer, and drain the compressor to get the oil out, you should also flush the lines, evap and cond. put correct oil in system and vacuum it down to -30in, see if it holds a vac for atleast 15 mins, if it doesnt then you have a leak and need to find it. if it holds vacuum it down for atleast 30 more mins to get all the old freon and moisture out. then fill it with 80% of r134 as you would r12. but without gauges you cannot diagnos some problems if it doesnt work after all that. if a system is left open for a long time 1yr plus i repalce the evap, cond, and comp just to make sure.

sorry for the terrible spelling
Click to expand...
Quoted for truth! I used to run an A/C shop in N. Idaho and we did ALOT of conversions. We did everything Scott said except for the o-rings and seals unless they were leaking. Everything else is spot on.
 
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