Any A/C experts out there?

Doug_Scott · May 6, 2012

Sorry hit send. Vacum pump. This will remove moisture out of system. According to size of pump how long to evacuate system. Plus outside temp. But I would pull vacum as long as possible Less moisture colder air. Also it takes 15% less134 than R.12. Overfill with 134 and no cold air. You can find out how much 134 to use at parts house. Accumalator/dryer are not expensive here in miss 25.00 to 35.00 and they keep air cold by removing moisture. GOOD LUCK ! 96 degrees here today your gonna need good air this year

Just to add something to make it more clear... with a vacuum pump applied to the closed a/c system, once you get about 29 inches of vacuum, any moisture in the system will boil out. Water when subjected to about 30 inches of vacuum will boil at room temp. You keep the vacuum applied for 30 minutes to ensure all moisture is removed.

Rogue Leader · May 7, 2012

Hi all thanks for the replies. I was trying to mess with it to get it working before the race this weekend but I got too busy. Truck towed about 7000 pounds (in the bed plus car & Trailer)for a 6 hour drive there and back, pretty good for 208k miles original 350 in it.

What I did manage to do was empty 2 more cans in plus a can of oil. I figured out my problem being that you need to shake the hell out of the cans to get them to empty. What the compressor started doing was running longer before cycling, so I figured one more can may do it, but I got too busy. That said it may all be leaking right out as well, but I am able to get vaguely cold air out of it.

I'm gonna try one more can and see if it stays on, and if so I'm golden, if not I will start working on what is described in here and see if I can get this working.

jseabolt · May 14, 2012

I'm not an A/C expert by no means but I did put together an A/C system for my Fiat Spider using parts off Ebay about a year ago.

http://s222.photobuc...ider AC system/

I asked an A/C tech about charging it up for me and he said if I built the system, he would tell me how to charge it. Which was a surprise because most A/C techs want you to believe they are the only ones who are qualified to do it. He also had no idea how much R134a to add because it was a custom system. He said the least it would take was probably two cans.

I pulled vacuum on the system for 30 minutes using a vacuum pump I got at Harbor Freight for $12 and added one can while monitoring the temperature and pressures. At around 92F, the temperature coming out of the vents was around 45F and 40 PSI on the low side. I added a second can and saw no difference in pressure or temperature. So I stopped at two cans.

Who knows I could probably add a third can but didn't want to overfill the system.

There is supposeably a formula out there where you figure in the condensor size, evaporator size and length of hoses and it will tell you but I haven't found it yet.

My 76 Chevy truck has a aftermarket system with a monster York compressor and I'm going to convert it over to R134a this summer. A new dryer is in order and I'll probably take the compressor off and dump the R12 oil out and replace it with R134a oil.

However I had a 96 Explorer that was doing funky things. The compressor was cycling on and off every one second.

Although it was reading something like 30 lbs on the low side, an extra can did not fix it. That turned out to be a clogged orfice tube and a bad low pressure switch.

By the way. Sometimes you can find good deals on R134a at Big Lots. Last summer they got in a big shipment and I picked up several for $8 a can! I decided to buy $100 worth.

I had three cans of R12 I had been hanging onto since the early 90s and decided to sell them on Ebay and got $80 for them. I paid $2.00 a can for the stuff in 1991!! So that supplimented my investiment.

Some say R12 cools better than R134a but the only advantage I have found is R12 oil does not cloud up the sightglass in the dryer where R134a makes it impossible to see if it's properly charged. In other words with R12 when you see no more bubbles, the system is charged. With R134a you pretty much have to know the volume, if not then the only other means is by pressures.

Rogue Leader · May 14, 2012

I went at it a little bit more this weekend but at this point I think I'm just tossing money (cans of 134) at it and not helping. I turned on the AC and the compressor didn't cycle. I added a can and the compressor cycled on and off about 10-20 seconds each which is longer than it was doing. I'm sure if I go try it in a week it will be dead which means theres a leak somewhere, but at least I know the compressor works.

I'm gonna replace the lines as suggested, I saw them for about $50 on rockauto, and maybe even the accumulator as well as it was like 15 bucks. To me it seems there must be a leak as the compressor does cycle so I see no need to replace it. I also put a link to the drier below but where is that located? I only see the accumulator on the firewall.

http://www.partsgeek.com/catalog/1996/gmc/k2500/climate_control/a-fs-c_hose.html

http://www.partsgeek.com/catalog/1996/gmc/k2500/climate_control/a-fs-c_receiver_drier.html

http://www.partsgeek.com/catalog/1996/gmc/k2500/climate_control/a-fs-c_accumulator.html

jseabolt · May 14, 2012

The accumulator and dryer are the same thing.

Have you connected a set of guages to the compressor and see what sort of pressures you are running? With R134a 40 PSI on the low side is supposed to be normal. I can't remember what the high side is supposed to read but the guage usually has a mark on it that tells if you are in the danger zone. Pressures will vary with ambient temperature but I did not find them to vary too much.

Since the compressor is cycling worse after adding another can, it maybe the high pressure switch that is kicking it on and off because there is too much refrigerant in the system.

I jumpered the low pressure switch connector on my Explorer and it seemed to help somewhat but because the orfice tube was clogged, the A/C would work intermittantly. I wouldn't do this unless I knew that I had 40 PSI on the low side.

Rogue Leader · May 14, 2012

The accumulator and dryer are the same thing.

Have you connected a set of guages to the compressor and see what sort of pressures you are running? With R134a 40 PSI on the low side is supposed to be normal. I can't remember what the high side is supposed to read but the guage usually has a mark on it that tells if you are in the danger zone. Pressures will vary with ambient temperature but I did not find them to vary too much.

Since the compressor is cycling worse after adding another can, it maybe the high pressure switch that is kicking it on and off because there is too much refrigerant in the system.

I jumpered the low pressure switch connector on my Explorer and it seemed to help somewhat but because the orfice tube was clogged, the A/C would work intermittantly. I wouldn't do this unless I knew that I had 40 PSI on the low side.

Gauge shows normal, its not overfilled. It was doing better with a can added. Basically in the past week i have been adding cans, getting it to cycle, and then I come back to it a week later and it doesn't cycle anymore telling me its likely leaking out. Its hard to get a true solid reading though since with the compressor only cycling you don't know if it has more to go.

jseabolt · May 14, 2012

A guy I used to work with he took over his father's heatpump business says he uses stop leak in systems with hard to find/slow leaks. He says it works.

He was supposed to come back and add some to my heatpump but I haven't seen him since!

I'm pushing 27 years out of an old Trane heatpump. The problem is when the system is in heatmode, the evaporator becomes to condensor and is then on the highside so it leaks 2 lbs of refrigerant out every winter. But holds a charge as long as it's on cool mode. That coil has some serious electrolysis going on with it after 27 years being it's made of steel, alumnium and copper.

He told me Trane no longer makes replacement inside coils for this model and I'd have to get a custom one made which costs $1000!!! Or just replace the system. I'm going to try to stop leak method. The system is running on borrowed time anyway,

Rogue Leader · May 14, 2012

A guy I used to work with he took over his father's heatpump business says he uses stop leak in systems with hard to find/slow leaks. He says it works.

He was supposed to come back and add some to my heatpump but I haven't seen him since!

I'm pushing 27 years out of an old Trane heatpump. The problem is when the system is in heatmode, the evaporator becomes to condensor and is then on the highside so it leaks 2 lbs of refrigerant out every winter. But holds a charge as long as it's on cool mode. That coil has some serious electrolysis going on with it after 27 years being it's made of steel, alumnium and copper.

He told me Trane no longer makes replacement inside coils for this model and I'd have to get a custom one made which costs $1000!!! Or just replace the system. I'm going to try to stop leak method. The system is running on borrowed time anyway,

One of the cans I loaded had stop leak in it. I would assume the leak was too much to stop as it still doesn't work.

Rogue Leader · May 17, 2012

Ok parts are ordered, got the accumulator and hoses. Hoping this will cure it. I would assume if theres a leak its from there as I'm not running the AC but it sure is running out of refrigerant.

Rogue Leader · May 29, 2012

Well that was a bust, got the accumulator and hoses. Went to detach the hose from the condenser, its not budging. I think I'm gonna need to buy a new condenser as well.

Doug_Scott · May 30, 2012

Well that was a bust, got the accumulator and hoses. Went to detach the hose from the condenser, its not budging. I think I'm gonna need to buy a new condenser as well.

If the system is empty, you can heat the fitting with propane torch, do not try to get it red, it won't go red, it will just melt away. The system has to be completely empty. Refridgerant and a flame makes phosgene gas, you don't want that.

The compressor front seal is a common leaking point, if you have oil staining behind the front pulley, or wet grime there, chances are the compressor front seal is leaking.