I know nothing about the system in my truck. The pump doesn't have a belt on it and when I spin the pump, it sounds like I'm shaking a jar full of ball bearings. I'd say that's pretty much puked. I think these old rigs had R-12 refrigerant. I think I need a new pump, but if I get a new pump, that means R-134a refrigerant?

Also, I notice there's an electrical receptacle or connector in the pump, but I cannot find a wire or connector that goes to it.

Is there any other part of the A/C system that takes refrigerant? Do I have to do a major overhaul to change refrigerants? Where should I start?

 

if you get a new pump, you can still get r-12 but you have to take it to a a/c shop to fill it. big mistake though, with the price of it vs r134a you would be crazy to stick with r12. the plug on the pump is the power for the clutch. the belt pulley spins freely, until power gets put to it then the clutch kicks in and spins the pump. the whole system gets filled with the charge. only thing you have to do when you convert to 134a is a can of oil thats called "first charge oil" autozone, kragen ect will have it. then a few cans of the 134a. synthetic is supposed to be a lot colder. standard works well though. cold as hell in my truck.

 

oh, and the plug that goes into the pump comes off the harness that goes to your alternator, tack sensor and a/c compressor. all one line.

 

also, you need the conversion tips. its a 3 piece aluminum pack, about $14. it just threads onto your high and low side fittings and turns it into a schrader valve type system. the a/c charge valves just chuck right onto it like your air compressor fittings. and the fill will only fit on the low side, so you dont gotta worry about that.

 

Can I just buy an R-134a ready pump? Is the pump the only deal that takes refrigerant?

I'll have to look around for that wire and connector. There's some wire that's all taped up on top of the alternator wire. That's probably it.

I thought it was the seals that need to be replace in order to handle the hire pressure for 134a

 

The compressors are the same for either R12 or 134. But you want to match the oil to the type of refrigerant you are using. The compressor you buy should give you a spec on how much oil to add to it. The oil will circulate through the entire system for lubrication. Each component has a certain amount of oil to add, but it depends on the vehicle.

The system pressures run pretty close with 12 and 134. But on a system that hasn't been used in a long time, it is a good idea to replace as many of the orings that you can now with the system open to save trouble down the road.

I would replace the compressor and clutch, accumulator/drier, orifice tube, orings, and install the conversion fittings. And then take it to a shop to have it pressure checked, evacuated (vacuumed) and recharged with R134a.

Early 134 conversions didn't work as well. I'm not sure if they have changed the formula for it, but I have had good luck with 134 in R12 systems. On an 85 deg F ambient, a typical system might get to 40-45 deg F. On a really good system, I've seen them get down to the mid to high 20's. But that is pretty rare. I've heard that if you can get 30-35 below ambient, that is sufficient.

Jason

 

Gotta swap the oil in refrigerant for the change to r134a. the seals aren't always compatible either so you'd need to swap them.

if you take it apart try your best to seal off the lines you don't want air/moisture in the system if you can help it.

Been a long while since I was into HVAC but I'll try and rmeember more

 

Do they sell a kit to install new seals and o-rings wherever necessary to make the conversion a success?

 

just measure the old ones and order some more that are 134a oil compatible. I don't know if there is a kit you can order with everything you need to convert it. just some homework to do on it

 

I've been so busy with other stuff I have not been able to take care of my A/C.

I spoke to a guy at work yesterday and found out he's licensed for handling R-12 (HVAC Journeyman Tech)... Should I just replace the bearing in my pump and get an o-ring kit to reseal everything and have him charge it w/ R12 or just buy new and go R134A?

Sorry for the random questions, but knowing this guy handles R12 changes variables / options.

The electrical wire and harness that connects to the pump is MIA. I can't hunt it down. It appears to have been removed.

What's and Orifice Tube/Expansion Valve and Drier? I need to replace them in order to prove any warranty claim on a new or rebuilt unit.

 

R12 is like liquid gold. It will cost you a lot to charge it. (At least with actual R12) R12 is an ozone depleting refrigerant and was therefore put on the chopping block years ago. No new R12 freon has been produced in the US for years. This means virgin R12 is either EXTREMELY rare to find, or brought in from other countries in a black market. In either case it's $$$$. Most of the R12 that does get recharged is reclaimed/filtered/dried R12.

R134a is the standard in cars now. As mentioned before you can run R134 in an R12 system. Napa sells an R134 conversion kit that has everything you need (including the new HNBR O-rings) If you're converting to R134a make sure to get a new accumulator (receiver/dryer) that has R134 compatible dessicant.

The connector on the front of your compressor should have 2 leads. One lead goes to the black/yellow striped side of the pressure cycling switch on the accumulator (the power side of the switch should be a light green and should have 12v when the fan is on and the a/c is on) This switch will keep the compressor turned off until there's some pressure in the system so you'll have to get some charge in it first before it'll start running. The other lead from the compressor is grounded out to complete the circuit.

The "Drier" is the big round can thing on the passenger side with the switch on it. The big suction line to the compressor attaches to it.

The Orifice Tube and Expansion Valve are two different items but one of the same. Our trucks use an orifice tube. An Expansion Valve (Sometimes called a TXV for Thermal Expansion Valve) releases the freon at a rate based on the evaporator temperature. An Orifice Tube just releases the freon at a controlled rate.

Think of the Orifice tube as a plug in the system with a tiny hole drilled in it. The compressor pumps the freon up in pressure (The "High Side" typically will be around 175-200 psi depending on temp and humidity etc). The freon exits the pump on the Discharge side (sometimes marked with a D, on our trucks it's the passenger side of the pump) Pressurizing it all builds up a lot of heat and so the next stop is the condenser up front. This cools the freon down and causes it to condense into a liquid - hence the name. After it exits the condenser it travels to the passenger side through a smaller high pressure line. It's next stop is the orifice tube. The principle in how it works is just like why a gas grill tank gets cold when you use it. The orifice tube causes a pressure differential in the system. The high pressure liquid on the high side of the orifice tube squeezes through the orifice tube to the low pressure side. When it hits the low pressure side the freon evaporates, which is what causes the cooling effect inside the Evaporator (Hey another part appropriately named!) When it comes out of the evaporator it's next stop is the accumulator, also known as the receiver/dryer. This items purpose in life is to remove and trap any moisture in the system. Moisture inside the a/c system is no friend and can cause quite a few issues. As stated before this is also where you'll find the a/c pressure cycling switch. And after it's trip through the accumulator it's off through the big hose back to the suction side of the compressor (drivers side)

If the a/c system has been open to the air for quite some time you'll want to make sure the lines are all clean and pull a vacuum on the system for at least 30 minutes before you charge the system to get the moisture out.

As Oreo stated, you can get R134a recharge kits at walmart and parts stores in SOME states (ok, MOST states) A few states (like Wisconsin) are retarded and even though it's not an ozone depleting HCFC like R12, they put a full on ban on refrigerant requiring a federal/state MVAC 609 certification to buy the stuff. So I bend over and buy it in the 30lb canisters (about 175 bucks right now) Fortunately they do quite a few cars and last me a few years.

I just did the R12>R134 conversion last night. I'd say maybe 2 hours in total to replace the accumulator, the o-rings and the oil. Then pull a vac of 30inHg for 30 min and then I let the system sit under vacuum for at least 15 minutes to check for leaks before I charge it. It was much nicer driving it to work today. But then my speedometer started acting up...

Oh and if he'll recharge it, he may recharge it with an R12 replacement, such as Freeze 12, or one of the other handful of replacements. I'm pretty sure R12 is controlled in every state requiring a certification to get it. Both type 609 MVAC and 608 HVAC certs can get R12 I think.

 

Awesome write up and explanation!! Any chance you can take some, pics of the process to do a swapover? Changing things like O-rings etc are something (in a drained system) that most of us should be able to do, even if we then have to get an AC tech to pull the vacuum and recharge things after.

I know I'd like to learn how to do them properly, so many places want to charge high prices to 'throw a can in' and it only lasts a short while anyway.

 

i dont understand why all the hassle.for $80 you can just buy freeze 12 and be done.
i seem to remember spending more for my car than that when i recharged its 134a system.
i dunno.im just going freeze 12 mech.

 

after you convert your system its only $30 to charge your system with 134a. in the long run its a better option.

 

All right, now we're talking.

FORDF250HDXLT, when I spin the pump sheave, it sounds like a jar half full of nuts and bolts being shaken vigorously. Something is obviously wrong and I can't just recharge it with R12 and expect it to work.

What is done when the A/C pump is "rebuilt"? Do they just replace the sheave bearing, o-rings and seals you get in the conversion kit and repaint it?