I have a 75 with factory A/C that presently does not work.

Compressor seems to work fine [no squeal, no noise] when the low pressure cut-out switch is jumped with a cotter pin.

This tells me it needs a charge.

Before charging, I plan to vacuum the system down for 45 minutes. I'd like to let it sit for a while to make sure there isn't a drastic leak in the system. I have a 134 retrofit I will be installing, which basically consists of fittings and oil.

My biggest question in this whole job is how many pounds of 134 should I anticipate? I'm charging from a 20 pound tank, so I need to know weight as opposed to the number of cans...

Thanks in advance. The forum has been great since I joined about a week ago. The hot/warm interior threads have been very insightful with my trying to get to the root of that problem.

 

cvd,

i'm no know it all but i do know a bit about automotive hvac systems.

to answer your question about the charge of 134a, it needs to be 80% of what the charge for r12 was. it should tell you this in your retro fit kit i'd think.

what kind of retro fit kit are you using? something off the shelf at pep boys is not the way to go. you will introduce air into the system which is an enemy of air conditioning systems.

i would hold the vacuum on that system for more like an hour. sounds like the system has probably been discharged for some time. you will need to replace the accumulator (or receiver dryer--i'm not sure what these cars have since mine is not a/c) b/c the dessicant in the accum. is old and will not react well with the new refrigerant. also beware that in all likelyhood the o-rings are dried out and will need to be replaced. change out the metering device too (cheap insurance).

i guess that's not really a quick reply but i hope it helps.

kbosland

 

I also am having A/C problems..it's a 134a swap as well...told previous owner the a/c wasn't working, response..."was working fine last summer"....OK, needs a charge, get a can at Advanced Auto, open valve to the highest green on tank meter...no cold...well more is better...right? Up it past the green...Well...the compressor starts making a horrible squealing noise, the idle drops to almost stall...like the compressor seized...removed the charging connection thingy, I assume I lost the 134a and everything went back to normal, or at least the way it was before I messed with it....probably blew up the compressor...and at some point I will take it to an a/c shop and face the music...I obviously do not understand this a/c stuff...
Anyway...maybe just take your car to the shop and avoid my blunder

 

with beer, more is better......

with AC refrigerant, more is not better. refrigerant needs to be at a specific ammount. too little is bad. too much is also bad. r12 is a little more forgiving than r134a as to the exact charge ammount required. when charging with 134a, sometimes you have to creep up on that perfect charge ammount.

when i was learning about this stuff, most people refered to these quick fix kits from pep boys and others as "death kits." mainly becuase they are a sure fire way to kill your system if done improperly. you are much better off getting a set of gages and doing it a little more properly.

ac systems are just like engines. it isn't always such a good idea to just jump in and try something. research it, ask questions, and learn something about it first so that you can do it once and do it right.

 

I know you have already purchased the parts for the retrofit, but I have to say you'll be better off in the long run having your system repaired properly and use R12 in it. The pressures with R134a are higher and it doesn't have the cooling ability because of that. R12 is available without any problem, sure it's a little more expensive but you're better off with it over the long haul.

Mine wasen't working either, turned out to be a bad hose. I replaced it and rebuilt the VIR valve at the same time and the system works as it was designed.

Good luck

Bill

 

I know a little about air conditioning (theory wise) but have zero experience working on them. Business has been slow and I do not want to spend more than I have to. That means I want to spend as little as possible but only want to do the job once. You are saying to replace the drier. I saw that Napa and Advance Auto both sell the dessicant in a kit for slighlty more than $20. This is a saving of $60 to $90 versus buying a rebuilt drier. Is there any reason why I should buy a whole assembly versus just a dessicant kit? Another question is in regards to o-rings. I believe there are a couple of them on the back of the compressor. Does anyone know where others are located and is this something you walk into a parts store with and they match them up? And one final question. When connecting the fitting, should any type of material such as teflon tape be used?
My system had a small leak and was esentially empty when I pulled the engine 6 months ago. I am planning on using the R12a and like original poster, I have no idea as to how much to put in. A freind works on HVAC systems and will probably have him charge the system but he works on residential/commerial buildings.

<http://www.partsamerica.com/ProductList.aspx?PartType=397&PTSet=A&Se archFor=Receiver%20Drier%20%2F%20Acumula tor>
<http://www.napaonline.com/masterpages/NOLMaster.aspx?PageId=430&Keyword=drier& KeywordCat=AC+VIR+Assembly&VehCode=Y>

 

Yup, you're right mdj21...with beer, more IS better
I found out the hard way, it isn't with a/c
BUT, in the same sense, I won't try brain surgery either...so the bottom line, take it to a shop and get either bad news or good news...besides, up here in NY, you get maybe a week or two of oppressive weather and then it's just 255 weather... (2 windows down, 55 mph) altho with the vette it might be 285

 

[QUOTE=mandm1200]I know a little about air conditioning (theory wise) but have zero experience working on them. Business has been slow and I do not want to spend more than I have to. That means I want to spend as little as possible but only want to do the job once. You are saying to replace the drier. I saw that Napa and Advance Auto both sell the dessicant in a kit for slighlty more than $20. This is a saving of $60 to $90 versus buying a rebuilt drier. Is there any reason why I should buy a whole assembly versus just a dessicant kit? Another question is in regards to o-rings. I believe there are a couple of them on the back of the compressor. Does anyone know where others are located and is this something you walk into a parts store with and they match them up? And one final question. When connecting the fitting, should any type of material such as teflon tape be used?
My system had a small leak and was esentially empty when I pulled the engine 6 months ago. I am planning on using the R12a and like original poster, I have no idea as to how much to put in. A freind works on HVAC systems and will probably have him charge the system but he works on residential/commerial buildings.

mandm1200
I'll try and answer your questions briefly but i don't want to hijack CVD's thread:
to be honest, i didn't know that any parts stores sold a seperate dessicant kit. what i would ask is, how do you get the old dessicant out of the old accumulator and put the new stuff in? in my experience(i've worked on a few) the unit (accum or receiver/dryer) is one piece. the old dessicant is something like X5 which will not work with R-134a refrigerant. New dessicant is either X7 or X9. i believe that trying to save money on an a/c system repair or upgrade is really wasted money in the long run. believe me, i know what it's like to not have the money to spend on the vette. i won't begin to tell you my story. a rebuilt dryer or accum. is well worth the extra insurance. new is even better than that.

as far as o-rings go--yes, there should be a couple on the compressor where the suction and discharge lines go. the other ones will be wherever hard lines are joined together. you can take them out and bring them to a parts store to match up. it shouldn't be that difficult to find these i wouldn't think.
As far as the fittings are concerned, the answer is NO! (Don't mean to shout just emphasize). You don't need any kind of thread sealant when connecting a charging machine to your R12 fittings and you should never use any on a retrofit to R-134a.

you want to know how much R12 to put in right? Ideally, there should be a sticker under the hood of your car that tells you this info. I'm assuming that's long gone. I would check out a Haynes or Chilton's repair manual. If you don't have one, maybe someone on here can look it up for your car. I have a Haynes for 68-82 (I think) and i will try and find it for you.

Lastly, if your friend doesn't use R-12 to charge A/C systems in those residential and commercial buildings and you're not doing a retrofit, then pony up the $$ for R-12 from a shop. It will cost a bit but the so called "replacement refrigerants" like R-22 and such are not approved by the EPA for automotive use (no i'm not a tree hugger just telling ya what i know) and worse yet, if you have to have this system worked on by a repair shop down the road, most likely a good one won't want to touch your system if they find different refrigerant than either R-12 or R-134a.

Phew, that was long (hope this helps you too CVD) hope it works out.

kbosland

 

The place to go for information on a/c is this forum.

http://www.autoacforum.com/

These guys are great. Will help you out. Its like the corvette forum for
a/c....

 

well i guess everything has gone up since i was a kid. we used to call it "using the 440 AC." (4 windows and 40 MPH.)

 

mandm1200

i checked my haynes manual and there was no spec. for the refrigerant charge. there has to be somewhere that you can find this. sorry i didn't have it.

kbosland

 

I have chilton book. I not at the stage of charging the system back up. Cleatus Van Damme originally brought up the question. I didn't want to hi-jack the thread but since I had had some questions that were related to this thread I though I would ask them here instead of starting a new thread.
Going back to the dessicant, I am not sure what that stuff is. But evidently it is replacable in certain uints. Napa part #TEM208517, which is made for part #TEM261501. Looking at the unit, it looks like it should come apart.
In another thread I read that there are other replacements for R12 other than R134a, which cool better than the R134a.

 

I think I'll take everyone's advice and stick with the R12 in lieu of swapping it out to 134.

I had the vacuum on the system last night and it wouldn't drop below a few pounds. There's obviously a leak. We'll start by pulling the hoses and replacing all of the o-rings. Since I'm going that far, I'm reading other posts that the VIR should be serviced or replaced.

Is the re-build as good as a new unit? The rebuild kit from Ecklers shows a few o-rings and new desiccant, along with a couple of odd looking small parts. The rebuild kit is like $30 and a new VIR unit is $120. I just don't want to go through the hassle and expense of tearing everything apart to re-build the VIR and go through the entire process again, only to find that I should have bought a new VIR to begin with...

Also, Ecklers is showing a VIR elimination kit. What's the difference between the elimination kit and the VIR?

It's not that money isn't a issue, I just can't stand doing the same job twice because it wasn't done right the first time.

 

I have a 76, and the VIR thing is located behind the fender on the passenger side. It looks like a royal pain to get out. It seems the air conditioning was the last thing GM 'engineered and stuck this where there was room. It was definetly installed before the front end was put on. I just had the interior apart for the heater core and removing this item seems to be twice the job. From what I can tell the evaporator will also have to come out which means tearing the right side dash apart.
If you do yours, can you let me know how its done?

 

Me and my BIL looked at this last night. Didn't look to be overly difficult to get out, we both think if you pull the coolant recovery bottle we'll have enough room to slide it up and through the hole.

Haven't tried yet though. There may be some other readers out there with experience in this. I am not in favor of pulling the dash and the heater core box.... That's more of a winter/off-season project.

 

A/C is for mini vans, not hot rods...

j/k..

 

Remove the front screw on the rocker panel to gain access to a couple of bolts that hold on the bottom shield right under the VIR. With the shield removed you can gain pretty good acess to the valve.

Bill

 

I was under the car getting ready to attach the new heater hoses. That's when I realized how to get it out. I removed the aluminum rocker trim and the four bolts that hold the sheild on. A couple of lines can be removed from the top and the remainder from the bottom. It came out but I know getting it back together will be harder. I took the bottom can off the VIR. All that is there is a tube sticking down with a mesh filter on it and a bag (must be dessicant). I plan on buying the $20 kit and reinstalling it, plus new O-rings.
I'm still not sure if I am going with R-12 or R-12a; certainly not going with R-134a.

 

R12a is a flammable substitute for R12 and is made from propane.

Bill

 

Now that's nice!!!

That's very good to know. I saw that in some of my searches and was going to consider it... but no way now...