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Questions on A/C unit in 1977 Chevy truck (annual A/C recharge time) *Resolved*

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Ancient4X4

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My annual summertime ritual has begun. My A/C is not working again. I purchased some bottles of R134a from the auto parts store. My truck was converted to the new stuff a couple of years ago. With the pressure gauge I got, it showed under 25psi. And the packaging said it should be between 25-45psi. So I thought okay, it just needs a recharge. So I put it to MAX A/C like the packaging says, I squeezed the bottle a few times and the pressure gauge seemed to stop working. So I put some more on. Then the pressure gauge started working. Now the compressor will still not come on, though it sounds like it is trying. The pressure gauge now reads about 70psi! :eek1: Which is just into the red on this gauge.

My question is why won't my compressor come on and blow cold air?
And is there a pressure release valve on this unit? There is a black valve on the side of the unit in addition to the blue one.

Also, what is the name of this A/C unit? I heard they are real pieces of crap. I'm going to go look at the manual and try and figure out if I have a blown fuse.
 
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Even though it will waste the freon, I think I'm going to unscrew the bottle and hook the gauge back up and attempt to aleviate some pressure.
 
Another thing when the A/C tries the engage, the pressure falls to nothing. That's what originally screwed me up I think.
 
Okay, after looking at it again, whenever the compressor kicks on with the A/C on MAX, the pressure goes down to almost nothing. Then the compressor turns off after two or three seconds and the pressure goes back up to 65psi+.

Does this mean I didn't add enough? I only added part of one 13oz can.
 
needs more, when the compressor isn't running it can be anywhere from 0(if it was empty) to 100 psi, when it engages, the comp should bring the low side to about 25 psi, you need to add more.
 
Thank you I wanted to update this thread, but I've been doing yardwork all night. I added two more cans after my last post. The compressor started working continueously once I got it over 25-30. I put two more cans in and it's around 40psi and now it's working great.

WooHoo!!! :D
 
Damn, wish mine was that easy. But my R12 system is blowing ice cold after a $600 recharge!
 
dhcomp said:
Damn, wish mine was that easy. But my R12 system is blowing ice cold after a $600 recharge!
Click to expand...

$600 to recharge an R12? Wow, I take it there was something else going on there with the A/C system besides just the recharge?

A couple of years ago I had my truck converted over to the new stuff, R22 I think. At first I thought I had made a mistake, since the air didn't blow as cold, but I think I made a good decision, now I don't have to mess around all the time trying to find a place that will recharge the old stuff for $$$. And the new stuff isn't as harmful to the ozone. If it leaks out I can fix it myself now :D I was at Big Lots earlier and I saw they had 12oz cans of R134a on the shelf for $5 each.
 
Ancient4X4 said:
$600 to recharge an R12? Wow, I take it there was something else going on there with the A/C system besides just the recharge?

A couple of years ago I had my truck converted over to the new stuff, R22 I think. At first I thought I had made a mistake, since the air didn't blow as cold, but I think I made a good decision, now I don't have to mess around all the time trying to find a place that will recharge the old stuff for $$$. And the new stuff isn't as harmful to the ozone. If it leaks out I can fix it myself now :D I was at Big Lots earlier and I saw they had 12oz cans of R134a on the shelf for $5 each.
Click to expand...


Yep, but its an a dual air Burb, so it takes 5lbs of charge. At $90 something a pound. Ouch. Hope it doesn't leak.

I was quoted like $1500ish to convert to R134a. :eek1:
 
dhcomp said:
Yep, but its an a dual air Burb, so it takes 5lbs of charge. At $90 something a pound. Ouch. Hope it doesn't leak.

I was quoted like $1500ish to convert to R134a. :eek1:
Click to expand...

Wow, thats insane. I hear people just evacuate it, change the ports and recharge with R134. Since I have a machine, I'm going to replace the accumulator, change fittings and charge it. My parts total was $28 for the accumulator and $12 for valves from Pepboys.
 
xCaliK5x said:
Wow, thats insane. I hear people just evacuate it, change the ports and recharge with R134. Since I have a machine, I'm going to replace the accumulator, change fittings and charge it. My parts total was $28 for the accumulator and $12 for valves from Pepboys.
Click to expand...

I was told you need to change out a lot more than that. but who knows. I'll cross that bridge while i get there. Right now my fingers are crossed that i dont' need a new trans :rolleyes:
 
I researched on the web and found most people just evac and change fittings with success. Porsche's had non/barrier hoses, so after you charged it, it would last about a year and leech theough the rubber hoses. R134 is so cheap and abundant that we would just top them off rather then rehose a car. I know you will never get all the oil out of the accumulator so its cheap and I will change it. The last conversion I did was on a 89 BMW 750i V12 and I changed the compressor too as per BMW, did it need to be done? Eh, who knows, but that was like 8-9 years ago. I'm going to do it on Saturday so I will let you know if it blows ice cubes, it won't blow as cold as R12, but should still be able to get it down to 4 degree vents. (provided it doesn't have a huge leak in something that isn't just an O-Ring.) I'll take some pics too.
 
Good luck! Recharging the r12 was pretty neat, cause it is COLD. Like, really cold.
 
R-12 definitely works better than R-22 and R-134a, but it is SO expensive now and of course, damages the ozone much more.

I went through old repair receipts to try and find out how much the conversion cost me, but I could not find it. However the $1,500 quote you received sounds like about 15 to 20 times or more than what I paid to have it done. I happened to find some cans of R-134a at Big Lots for $5, so I did add another can of R-134a to my compressor today, now it is over 40lbs. It does not blow as cold of air as the old system, but it is good enough. I took the P.O.S. plastic compressor gun/gauge back to O'Reilly's today as it was already breaking apart. Does anybody know where I can get a nice metal one?
 
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xCaliK5x said:
I researched on the web and found most people just evac and change fittings with success. Porsche's had non/barrier hoses, so after you charged it, it would last about a year and leech theough the rubber hoses. R134 is so cheap and abundant that we would just top them off rather then rehose a car. I know you will never get all the oil out of the accumulator so its cheap and I will change it. The last conversion I did was on a 89 BMW 750i V12 and I changed the compressor too as per BMW, did it need to be done? Eh, who knows, but that was like 8-9 years ago. I'm going to do it on Saturday so I will let you know if it blows ice cubes, it won't blow as cold as R12, but should still be able to get it down to 4 degree vents. (provided it doesn't have a huge leak in something that isn't just an O-Ring.) I'll take some pics too.
Click to expand...

I don't know much about this stuff, but when I had mine done the compressor was being replaced with a refurb at the same time, so maybe that made things easier for them.
 
If you don't have a Big Lots, I noticed while in Walmart the other day that they also have the R134a cans for $6.77, in case anyone needs to charge up. I didn't look to see if they had any charging guns, but if not your local auto parts store should.
 
It cost me 7.50 to charge my a/c at the dealership I work at.
 
Actually, R134 will get you as cold as 12. Not sure? climb in any late model top end car or truck that had 134 in from the factory and turn it on high. Just don't take your brass monkey in with you.
The reason the conversions usually fail to get as cold is because they were not designed to use 134.
The compressor is usually ok, and the metering system (orifice tube, expansion valve, whatever) will get the job done in most cases. Although there are some aftermarket things that claims to meter better.
What I have found to be the main problem with conversions is the condenser. (Air conditioner radiator)
R134 seems to store more heat per volume than 12. Which means that it gets heat-logged after a while because the stock condenser does not get the heat out fast enough.
A friend of mine who does a lot of the conversions in his shop has a source of supply for condensers that have more transferring capability than stock. More tubes, bigger, whatever.
He general rule of thumb before he starts a conversion, is that the bigger the car, or the more expensive, the less likely it will need a new condenser.
Full size Cadillacs, Lincolns, or anything used as a limo or hearse usually has a really oversized one to start with.
When we did my truck, we decided to try it without it.
It was just not quite good enough. But, I had a spare electric cooling fan, so I stuck it on and it made a big difference.
Even so, I'm going to get him to order me a new condensor which I will add the fan to for those really hot Fl. days.

J.
 
Fordum said:
Actually, R134 will get you as cold as 12. Not sure? climb in any late model top end car or truck that had 134 in from the factory and turn it on high. Just don't take your brass monkey in with you.
The reason the conversions usually fail to get as cold is because they were not designed to use 134.
The compressor is usually ok, and the metering system (orifice tube, expansion valve, whatever) will get the job done in most cases. Although there are some aftermarket things that claims to meter better.
What I have found to be the main problem with conversions is the condenser. (Air conditioner radiator)
R134 seems to store more heat per volume than 12. Which means that it gets heat-logged after a while because the stock condenser does not get the heat out fast enough.
A friend of mine who does a lot of the conversions in his shop has a source of supply for condensers that have more transferring capability than stock. More tubes, bigger, whatever.
He general rule of thumb before he starts a conversion, is that the bigger the car, or the more expensive, the less likely it will need a new condenser.
Full size Cadillacs, Lincolns, or anything used as a limo or hearse usually has a really oversized one to start with.
When we did my truck, we decided to try it without it.
It was just not quite good enough. But, I had a spare electric cooling fan, so I stuck it on and it made a big difference.
Even so, I'm going to get him to order me a new condensor which I will add the fan to for those really hot Fl. days.

J.
Click to expand...

So it's the condenser? I always figured newer cars that use R134a just have more of it in a larger compressor.
 
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