A C Mistake Made Today

[icanfixall]

So today I decided to recharge my AC system with R12 because I have lots of it and willonly use that. Our systems were not made for 134 but they do work kinda... Ask Towcat about that... Any way I pulled around 27 inches of vacuum and it held fine. So I added 340 grams of R12 on a dead system. Started the second 340 grams and turned on the motor so the ac pump would cycle. It did.... Then I noticed the freon stopped flowing out of the can.. Funny because it takes 4 cans or 3 lbs. My cans only show they are 340 grams per can. So anyway I'm feeling that something is about to happen when it does... The high pressure relief valve lets go so I bottle things up and shut it down. I have a new pump, orfice tube and everything worked fine before I did the serpentine belt changeover. I feel the high side discharge hose and it is hot.. The line going to the orfice tube is also hot. Now the system is about half full but things are not right.... Then I see what is wrong.... I don't have any air flow over the condenser because the fan is still off the truck..... Funny how just some air flow over the aluminum condenser will coll things down enough to work... So tomorrow I will suit up again and finish this off. Word to the wise... Don't think the ac will work too well without some air flow over the condenser....

 

[NJKen]

Id bet that is what your problem was. It takes some seriously high pressure to blow that valve open! Your lucky it didnt rupture the high side hose or gauge on the gaugeset.
Ken

 

[160k87F250]

Id bet that is what your problem was. It takes some seriously high pressure to blow that valve open! Your lucky it didnt rupture the high side hose or gauge on the gaugeset.
Ken

The pressure release valve is suppose to prevent damage to the other components. It should be OK. I gaurantee thats the problem. No airflow over the condenser.
John

 

[Truck#3]

I run a garden hose over the condenser to keep itcool

 

[icanfixall]

The garden hose seems like a good idea but what happens when your down and driving in traffic??? I have never had a reliefe valve open before but.. I always had air flow over the condenser too. Kinda funny how :things" really depend on each other to work.... I usually fill till the low side pressure reaches 55 lbs. Been doing it like that for many-o-years....

 

[towcat]

Id bet that is what your problem was. It takes some seriously high pressure to blow that valve open! Your lucky it didnt rupture the high side hose or gauge on the gaugeset.
Ken

letmee tell ya......
it's no fun at all when the system does vent. try sitting at a light in 120deg Barstow morning and all of a sudden all hell breaks loose under your hood and this noxious cloud pours out from every crack and crevice..........
R134 has higher pop pressures sooner than R12 does.

 

[RLDSL]

At the very least you are going to have to rig an electric pusher on there is you plan on going ahead with the fan experiment and you also want AC. You have to have air flow over the condenser of the head pressure will go bonzo just like that everytime you stop unless you rig a trinary switch in the pressure line that is set to cutout the compressor when the pressure rises and drops
You can install a switch in the high pressure line that you can wire the compressor clutch through that will shut it down when the pressure rises, or the switch can be wired to a fan to kick it on when the pressure rises.

 

[The Warden]

Just wondering, is the pressure relief valve meant to blow only once? i.e. if it blows, should you replace the valve (and, therefore, that part of the manifold)?

I've had my valve pop off a few times now, mostly from idling too long in hot weather. God, I wish I could afford to go back to R-12...

 

[DaytonaBill]

I've heard that propane can replace R-12 with satisfactory results, but I'm not sure about the orifice valve size??? You don't need a license to buy propane and you can vent it safely.

But even with this stuff, you still need air passing thru the condenser...;p

 

[sassyrel]

Just wondering, is the pressure relief valve meant to blow only once? i.e. if it blows, should you replace the valve (and, therefore, that part of the manifold)?

no, it will keep popping as nec---not a one time item--

 

[sassyrel]

I've heard that propane can replace R-12 with satisfactory results, but I'm not sure about the orifice valve size??? You don't need a license to buy propane and you can vent it safely.

not a good idea----and dangerous as h !!!

 

[NJKen]

I've heard that propane can replace R-12 with satisfactory results, but I'm not sure about the orifice valve size??? You don't need a license to buy propane and you can vent it safely.

not a good idea----and dangerous as h !!!

Vent a cloud of propane under the hood on a hot day and you will have a runaway diesel. really not good if you are sitting in traffic and have an automatice. The truck will simply run over whatever is in front of it.
Ken

 

[icanfixall]

What a differance a fan makes...... Oh yeah..... Here the tune now.... Anyway, I installed the fan today with plenty of blur loctite and torque. Let it set for an hour and started the motor. AC dropped pressure on the low side so I finished off adding the balance of the three lbs that it usually takes. No high pressure blow off or any other problems. That little bit of air flowing over the condenser really makes a big diffreance. I feel the charge is just a little low because I can't mearure what was vented so I will drive it and watch. The low side pressure is 45 to 47 lbs and the low pressure line going back to the compresser is cold but not frosty. Been there when I had too much R12 in the system and the heat trandfer was still happening in the low pressure hose going back to the compresser. Just a waste of good freon. Glad its up and runnin... As said before... "Things are looken up"....

 

[david85]

Yeah the fan does make a big difference. I removed mine for most of this winter and one weekend while I was checking everything I turned the AC on just as a mattery of diligence. I suspected there might be a problem with cooling so I kept an eye on it and sure enough it started getting warmer, not colder. Didn't let it get to the point of overheating and simply had the cycling switch unplugged for the rest of the winter.

Put the fan back on because I thought hot weather was comming and I wanted to be able to use the AC (yes, I know how that sounds!). All is normal now, but then the weather got cold again. It will actually make ice under the hood if I want to adjust it that far (duracool refrigerant).

 

[DragRag]

Most of you don't know this so I thought I would share. You can drop in other R12 replacements besides 134a. I have been using R409a for years. It acts just like 12, pressures are about the same. Charge liquid only due to being a blend. You must have an EPA license to buy it will be the draw back to the public, but if you have one give it a shot. Down side number two, 30# canisters only, no small cans. I always have it around, so no big deal for me being in the commercial refrigeration business. ANyway, just thought I would share that with you. If you are close to me, I am in Hollister Ca, I can give you a shot of it at my cost if you need. You come to me though if you need it. I can't buy you a jug though it is against the law for me to do so.