Quick HVAC Question

[zukirider21]

Hey guys, I'm replacing the ac compressor on a friends car. It's a 2001 mitsubishi eclipse 4 banger. The old pump was fine, just the clutch failed. The chilton manual says it needs 4oz of PAG oil, but i figure since i'm just replacing the pump, not all of the oil will be removed from the system. She refuses to take it to a place to get it evacuated and filled the right way, so i guess i gotta wing it. where do i put the oil? i know not all of it should go straight in to the compressor to prevent hydrolocking of the pump, but shouldn't a little bit go in to prevent a dry start? then where should the rest go? in the accumulator right? should I try to measure how much oil comes out of the old pump so i know how much was lost from the system? what happens if theres an ounce or two extra?

lastly, all i have is a basic recharge kit with a bunch of cans of r134a, it has a gauge, but i do not have a proper manifold setup. i'm pretty confident i know how to fill it, but if someone would be kind enough just to review the steps once more i would really appreciate it.

sorry for all the questions, i just dont wanna mess this up. thanks in advance!

oh and i know the accumulator should be replaced whenever the system is opened. but she refuses.

 

[gwaii]

this doesn't exactly answer your question,but why are you replacing the pump if it's just the clutch that's failed?while i haven't dealt with that particular model,i've replaced the clutch on many a/c pumps....without openning the system.

 

[03ranger4x4]

Hey guys, I'm replacing the ac compressor on a friends car. It's a 2001 mitsubishi eclipse 4 banger. The old pump was fine, just the clutch failed. The chilton manual says it needs 4oz of PAG oil, but i figure since i'm just replacing the pump, not all of the oil will be removed from the system. She refuses to take it to a place to get it evacuated and filled the right way, so i guess i gotta wing it. where do i put the oil? i know not all of it should go straight in to the compressor to prevent hydrolocking of the pump, but shouldn't a little bit go in to prevent a dry start? then where should the rest go? in the accumulator right? should I try to measure how much oil comes out of the old pump so i know how much was lost from the system? what happens if theres an ounce or two extra?

lastly, all i have is a basic recharge kit with a bunch of cans of r134a, it has a gauge, but i do not have a proper manifold setup. i'm pretty confident i know how to fill it, but if someone would be kind enough just to review the steps once more i would really appreciate it.

sorry for all the questions, i just dont wanna mess this up. thanks in advance!

oh and i know the accumulator should be replaced whenever the system is opened. but she refuses.

Find out how much oil came out of the original pump, and put that same amount inside the new pump. Now dont quote me on this, but you should put all the oil in the intake of the pump...Dont be to afraid to hydrolock the pump, and the intake port more likely then not, doesnt go DIRECTLY to the pistons/head of the pump. Reason being, if the intake and exhuast of the pump were sealed from the rest of the pump then how would the systems oil be able to lube the rotating assembly of the pump? (i.e. the connecting rods, bearings, etc) I would bet that intake is the side not directly connected to the pump itself on the inside, or else the pumps case pressure would be that of the system highside pressure...which would make the seals work harder to keep the system from leaking....

I have never taken one of these types of compressors apart to see exactly how they work, but I do know that residental and commercial hermetic compressors have the intake of the pump open inside the casing and the exhuast has a hard line from the pump itself to the output tube coming out of the case....and how you fill those with oil is by letting the pump suck the oil up. I know cuase ive done this before, and the reason it doesnt hydrolock is becuase you would need to overfill the hell out of it for the oil level inside the case to actually reach the pumps intake port(s)...

As far as filling it, connect the line to the lowside port, WITHOUT starting the system open the valve and let the refrigerant flow in (keep the can upright, you only want vapor going in, NOT liquid), wait about 15-30 mins for the pressure to equalize. Then start the system and add the freon slowly until you get the desired lowside pressure. If it is not indicated on your guage, i think the correct pressure for lowside is about 130psi, again better to look that up as im not positive.

Just my two cents hope it helps.

 

[97RangerXLT]

as said, pour some directly into the pump suction port before putting it in the vehicle. turn the compressor by hand to circulate the oil a few times.

The reason to replace the pump/ clutch as an assembly is simplicity. most clutches you will have to shim them to make sure they are the right tolerances between the clutch material and the pulley. pain in the butt, and most pumps you can get with the clutch and pulley systems just as cheap as the pump unit itself. If it is just the clutch going bad, I would consider a new or junkyard clutch and do the shimming just so you don't have to evacuate a fully charged system.

Another way to get oil in is you can get pressurized oil charges (just like the freon can, but has oil in it only) and have it pulled in by the a/c through your manifold gauge set. but if you are replacing the compressor, you want to make sure to add oil manually before it goes in to protect teh pumps.

AJ

 

[97RangerXLT]

After re-reading your post again, I would ONLY replace the clutch. if she refuses to have the accumulator/dryer replaced, you are asking for a failure down the road. any time you open a system you allow moisture to get in. most of this you will remove when you put the vacuum on the system prior to filling it, the accumulator dryer gets the rest. if you don't get the moisture out, it will freeze up and cause your compressor to lock up intermittantly, and then eventually fail. most accumulator/dryers are around 20 to 30 bucks, maybe 70 if it is one of the expensive ones.

So unless she is willing to put a bit more money into it, just replace the clutch...

AJ

 

[97RangerXLT]

Here is a link to a write up that I did for the Dodge intrepid A/C repair. much of this will be the same in theory to what you are doing, you will just have to modify some of the tools and repair methods to match the car you are working on... but the A/C system in general works the same..

http://www.lhforums.net/forums/showthread.php?t=5520

 

[kimcrwbr1]

I dont know it sounds like she is setting you up. If you drain the system charge you will need to evac it before you add any refrigerant and you can add the oil while it is a deep vacuum or put it in the accumulator before you vac it down. It is recommended you put a new filter drier any time you open a system up and take it into a deep vacuum for the specified time to remove all the moisture. Do it correct or she will blame you when it takes a dump do the research and you will need a vacuum pump or tell her you wont do it. It will fail and destroy the compressor and fill the system with acid. one drop of water is all it takes.

 

[adsm08]

Hold your old compressor upside down over a container of some sort. An old measuring cup is a good choice. Spin it over by hand until no more oil comes out. That's how much to put in the new one.


Also, the drier doesn't need to be replaced just because the system is opened. That used to be true, but modern ones can be exposed for up to a week before exposure destroys them.

 

[LearjetMinako]

If the A/C clutch is gone out, replace just the clutch. But if you insist on replacing the compressor, the compressor comes pre-oiled with usually 2oz of oil in it. Add the rest of the oil in the acculmator/drier.

 

[03ranger4x4]

I dont know it sounds like she is setting you up. If you drain the system charge you will need to evac it before you add any refrigerant and you can add the oil while it is a deep vacuum or put it in the accumulator before you vac it down. It is recommended you put a new filter drier any time you open a system up and take it into a deep vacuum for the specified time to remove all the moisture. Do it correct or she will blame you when it takes a dump do the research and you will need a vacuum pump or tell her you wont do it. It will fail and destroy the compressor and fill the system with acid. one drop of water is all it takes.

Will moisture create an acid in the system? Just wondering, becuase when i was in school for this i dont remember them saying anything about water making acid. The two things i do know for sure make the system acidic is the wrong type of oil (r-12 oil in an r-134a system for example) or a winding burnout, which is obviously impossible on a belt driven compressor...

 

[zukirider21]

alright guys well i got everything together, filled it up, and it seems to be blowing cold, but the compressor is cycling on and off ALOT (every 5 seconds) and im not quite sure what to do. at first, i thought there was too much refrigerant in there so i let a little out and it seemed to cycle with longer intervals. but now im down to basically 10 psi in the low side while its running. this cant be right? oh and its about 25-30F out here so i know it's gonna be a bit lower than when its warm out, but 10psi just seems too low.

 

[97RangerXLT]

fast cycling is usually an indicator of low refrigerant. but i would not mess with it until you get a day over 70 degrees to test it...

aj

 

[97RangerXLT]

your ac refrigerant pressure is highly dependant on the outside air temperature, and to get a truly accurate reading the outside temp needs to be above 70 degrees.

AJ

 

[zukirider21]

yeah thats the conclusion i ended up coming to. it's too damn cold to get a proper low side reading. i could pump a ton of refrigerant in to get the right low side pressure now and i'm sure it would cycle properly, but then when it gets warm out there's gonna be too much pressure and the hi side pressure shutoff is gonna trip. so i just left it at about 15lbs low side while running. worst case ill top it off when it gets warm out.

the funny part is as soon as i gave her car back, a TOTALLY UNRELATED check engine code came on within 10 minutes of her driving it, making me look like a douche and a half. i had to try to explain that p0421 catalyst inefficiency has nothing to do with the ac system hahaha

i cant thank you guys enough, you really saved my ass today. god i love trs and how you can get multiple top-notch articles of advice within minutes of asking your question. i think im gonna go for a premium membership one of these days

 

[BRUTUS_T_HOG]

She refuses to take it to a place to get it evacuated and filled the right way

don't even do it. the a/c will never work right unless you evacuate all the air out and remove the moisture from the system.

most new pumps come pre-filled with oil so its USUALLY just a quick remove and replace.

also if you don't replace the o-rings that you disturb there is a high chance they will leak.

your basic recharge kit might fill the system, probably not enough or maybe too much.

i'd just replace the compressor and drive it to a shop to have it evac'd and recharged correctly, then you can't be blamed when the new compressor and the entire a/c system fails from the acidic sludge that is created from moisture mixing with PAG oil.


OR

just replace the clutch