PUT A/C oil high or low pressure side?
 

I just replaced my evaporator on a E320 Wagon 1995 and I am going to replace the compressor and dryer.

I researched the forum and manual and I need 120 ml of PAG oil of viscosity of 46!

Now the question is weather to put 60 ml into the high pressure side and 60 ml in the low pressure side or everything in one port and if does it matter which?

Thanks... Are there good instructions for a DIYer to charger the system. I have a pump and gauges. ... I would like to charge it with exactly the right amount but doing it with cans seems a hit and miss!

Thanks...

When I did this task on my 95 wagon, the A/C tech added the oil through the low side port. If you haven't changed the drier yet, it's a bunch easier if you remove the left side headlite assy.

With the system open and thoroughly flushed, distribute the oil with a little in each component such that it totals the proper volume. Put some in the evap, some in the condensor and some in the filter/drier. You can put just a little in the compressor.

After everything is all together before evacuation, turn the compressor 12 or 15 revolutions by hand to make sure it is not liquid locked.

How does liquid lock a compressor?

Tries to move through the outlet, but can't get there in time, causing damage to the hard parts.

I had a compressor apart and I don't see how that can happen. The reed valves should let any liquid just pass right out.

Fluids are not compressable, that is why your hydraulic brakes work.

I'm well aware of the almost incompressability of fluids. But the A/C compressor is not your brakes.

So...Chas,
 

Prove us all wrong ,fill your compressor with 2 Oz of Lubricant,
(Don't bother Vacuuming, the Compressor Will Blow),fill with refrigerant and
turn on the A/C.

Get back to us on your empirical results.

Why would I do that?
I already posted that 2oz of oil had been added to the low side by the A/C tech. Or can't you read?
BTW, the results are excellent.

It's not a smooth flow of fluid, or you would be correct. It is a very sharp impulse and the oil has too much inertia to just start moving so fast, if the chamber is full.

Aha! The oil has more inertia than gas. That makes sense.
It's nice to get a reasoned response to a question-Thanks.

Okay, just fill the compressor with liquid, don't turn it by hand to ensure that it is not liquid locked and crank it up. It's your compressor, so you have all the right in the world to destroy it if you like.

I would say that filling it with oil and not turning it by hand, you would have a chance of NOT liquid locking the compressor. I suggested, as you would find on any a/c web site, that you turn it by hand to ensure no liquid is present to destroy the compressor. I suggested this as a courtesy by sharing my personal experience with you in an effort to save you a compressor. That's what we do here on this site. We try to help each other.

For those who don't believe that we know what we are talking about, they can tell us that we are full of it and do what they like.

As to liquid lock being impossible because of a reed valve, how do you think that the compressor COMPRESSES? The reed valve closes on the compression stroke. With liquid in the cylinder something has got to give. Even if it's the reed valve that gives, you will still have to replace or repair the compressor. We are only trying to tell you how to prevent that.

Your explanation of a reed valve is completely wrong. A reed valve is a one way valve and offers no resistance to flow as the refrigerant is compressed. You don't know what you're talking about.

Okay, yes it's a one way valve. If it's direction is such that it does not seal on the compression stroke and rather RELEASES on the compression stroke, then tell me.... HOW does the compressor COMPRESS the refrigerant?

Please answer this question since I know nothing and you know everything, HMMMMM.....?

I'm not going to waste my time on your crap. Look it up.

ROTFLMAO

Okay, as you've already pointed out I'm stupid. Stupid people are unable to look things up. So, how about you just give me the quick summary?


Fella' the first time I ever saw a reed valve in a compressor was when I was about 12. I'm now 60 and during that time I've seen way too many of them. So PLEASE, explain to me in fourth grade language so that I can understand. How can you build compression with a reed valve that opens to RELIEVE pressure.

I might be old, but I'm sure that I've not yet seen it all, so enlighten me.

Answer
 

You do not add a full oil charge..
Drain the compressor, measuring what comes out. (write it down).
Drain the dryer, measuring what comes out. (write it down).

Add the two for a total.
I generally add 5 - 10 ML additional for system losses.

WARNING:
The only time you ever add a full oil charge is a totally NEW/virgin system..
A used system distributes oil throughout every component, and you end up with excess oil charge = reduced refrigerent charge.

excess oil charge ac compressor
http://www.google.com/search?hl=en&rls=com.microsoft%3Aen-us&q=excess+oil+charge+ac+compressor.&btnG=Search&aq=f&oq=&aqi=

excess oil ac
http://www.google.com/search?hl=en&rls=com.microsoft%3Aen-us&q=excess+oil+ac&btnG=Search&aq=f&oq=&aqi=

excess oil Air Conditioning
http://www.google.com/search?hl=en&rls=com.microsoft%3Aen-us&q=excess+oil+Air+Conditioning+&btnG=Search&aq=f&oq=&aqi=

Automotive Air Conditioning Systems
http://www.familycar.com/ac1.htm

Aircondition.Com
http://aircondition.com/knowledge_base/Home.html



Have a great day..

Dude, this thread is getting way messed up. A simple review of compressor operation clearly shows that the presence of liquid in a compressor (whether oil or refrigerant) would damage it in short order: http://www.mistermatic.co.uk/aircon/systems.htm

Hey - I did not want to cause a strom in a tea cup...
 

However, there is now confussing information on the thread..

From my perspective of doing the job and risking the compressor I am perfectly happy to turn it after I have added the oil that is the question...

I am putting in a new dryer and compressor and just replaced the evaporator!

I flushed the condensor and as many hoses I could get too without disconnecting the evaporator again..

The manual says add 120 mL to the compressor and 10 ml to the dryer which I planned on doing. The big question now is

COULD there be enough oil in the hoses to cause too much oil in the system to be ineffective!

I would appreciate some constructive contributions

I would need some answer pretty quick since I need to get my A/C going to get my wife of my back in this TN heat ...

thanks and cheer up...

Did you flush the evaporator? If not, and you put in the specified amount of oil, then you do indeed have too much oil in the system. The evaporator can trap a good bit of oil.

If I understand you correctly and you added the oil only to the compressor and the filter drier, then you should be able to disconnect the evaporator lines, immediately sealing them so as to minimize the amount of moisture that will reach your new r/d, and then flush the evaporator thoroughly. THEN thoroughly blow out the flushing agent from the evaporator and reconnect the lines.

Assuming that I understand correctly that you flushed everything else, then your oil amount should be okay. Since you added the oil the compressor, the last thing you need to do before evacuation or certainly before starting the system, turn the compressor by hand at least a couple of dozen turns. That much oil in the compressor alone requires you to be careful.

Good luck,

Add oil to the A/C system.... ?
 

Hi Forum gurus...

Here is how we started... (1995 wagon - E320) I had a leak in the evaporator

- therefore replace the evaporator

then I decided to change the dryer and the compressor before recharging the system.

I read the manual and it instructs us to put 120 mL of oil into the compressor but I was not sure weather the low or high pressure side ... I should have done some homework on how compressors work and then it would have been obvious to add it to the suction (low pressure) port.

Now the confusion started on the forum weather to turn or not to turn the compressor with THAT much oil in it!

Here is what I did...

I filled it with exactly the recommended amount of oil (120 mL) since I had a new evaporator, flushed the system and installed a new dryer (with 10 mL of oil as instructed by the manual).

With the compressor held in one hand I turned the compressor and oil started to come out the other port! I stopped turning and caught the oil dripping out. I added the oil which came out to into the hose connecting to the high pressure port. The oil which came out were about 20 mL. Not a big deal.

I assembled everything evacuated it over night. It pumped down fine and I wait till tomorrow to see if it will hold the vacuum.

So here is how I would answer my original question in retrospect...

- Make sure you flush the system and dry it completely with air...

- Now you can assume you have no oil in the system

- Add 120 mL to the suction side of the compressor...

- get it all connected AND the turn it by hand... a couple of turns to keep the excess oil in the compressor from causing a potential damage

- replace the dryer add oil

- evacuate and then refill

I hope this is helpful to generations to come!

Thanks Forum... there is no need to get aggregated :-)

Cheers

It sounds as if I was not clear about turning the compressor. What I mean when I say that is AFTER everything is all together with the correct oil volume et al, turn the compressor by hand. I did not mean to say to turn the compressor with everything disconnected.

Where are these arrogant people coming from these days? Why do we have to endure it? Too many of them. May be time to leave.

And if it were me, I would put the oil in the dryer rather than the compressor. Adding that much oil to the intake of a compressor makes me nervous...even if it won't hurt a compressor to put a liquid in it. :rolleyes:

I replaced the compressor in my '82 380SL about a month ago, and the instructions that came with the new compressor said to pour the entire amount of new oil into the low pressure side of the compressor, then position the compressor so that the nose of the compressor is pointed down and leave it that way for at least 15 min. to ensure that oil gets to the shaft seal, then turn the input shaft at least 15 turns, then install the compressor.
This info is right off the four seasons instructions. Not trying to dispute anyone's instructions here, just providing the manufacturer's instructions. Keep in mind that this is for the older style compressor, and may not apply to the newer style ones.

The two most important issues are that you have the right quantity of oil in the system AND that there is no liquid in the compressor to cause a lock. To prevent the lock you should ALWAYS turn the compressor by hand before starting the engine. Just do this as a standard practice after major a/c surgery.

Distributing the correct amount of oil throughout the system is good practice and at least a smidgeon the compressor so that it is not bone dry upon startup is also a good idea. Just pay attention to the criteria in the first paragraph and everything lubrication wise should work out okay.

:bsflag:

Truth is, what you are saying is backward. The valve offers resistance WHILE the refrigerant is being compressed. If there was no resistance as you say, the would be no compression - and we would not call the component a COMPRESSOR. I don't know what we WOULD call it, because it would be useless. Maybe we would call it a door stop or a paper weight.

The way you describe it would be like having the spark plugs fire in the engine while the valves are open, which of course does not happen since if it did, the engine would not run and produce power.

All this is rather obvious to anyone, I would think.

You are just toying with us, right?

The reed valve offer very little resistance. This practical experience of boudenfj is an example-
"With the compressor held in one hand I turned the compressor and oil started to come out the other port! I stopped turning and caught the oil dripping out. I added the oil which came out to into the hose connecting to the high pressure port." The poster was able to pump oil through the compressor by the hand. That would not be possible if the commpressor were bulig prssure internally.
If you've ever had a compressor apart, you would know the reed valves are made of thin material and could not be cause of any high pressure.
Pressure in the high side of an A/C system is not measured in the compressor but considerably upstream from it. That pressure is the result of throttling by the expansion valve.

OK, got it. It is not the compressor that compresses the gas and forces it through the condenser where in condenses into a liquid.

I have now learned that it is the expansion valve that does the compressing, and not the compressor.

Just curious. When the mixture in the engine is compressed before ignition, is it the muffler that actually does the compressing, through the miracle of back pressure?

An internal combustion engine is not an A/C compressor. Please start a new thread for those questions.
An air compressor would be a good comparison. If the outlet of the compressor is not connected to a tank, just venting to the atmosphere, there is very little pressure made. Connecting the compressor to a tank causes pressure to build. If we then connect an air hose to the tank and a blow-off nozzle, representing the expansion valve, we have cooled air-due to de-compression.
I hope you do better with the above explaination, because so far you have mis-read my previous post, and you have learned nothing.

I believe the question is about the compressor. Whether it is vented or not is irrelevant. It is still a compressor. The compressor compresses the refrigerant gas in an AC. The expansion valve does not compress the refrigerant, it simply meters the (now condensed liquid) compressed refrigerant into the evaporator.

Reminds me of an old saying...

For those who understand, no explanation is necessary.
For those who do not understand, no explanation is possible.

Have a nice day.

VERY GOOD!

Answer
 

FYI:

to flush or not to flush A/C ?
http://www.peachparts.com/shopforum/diesel-discussion/120649-flush-not-flush-c.html

Mineral Spirits as A/C Flush?
http://www.peachparts.com/shopforum/tech-help/166062-mineral-spirits-c-flush.html

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Question: COULD there be enough oil in the hoses to cause too much oil in the system to be ineffective!

Answer: If the system was flushed correctly, the answer is NO......

****************************************

Thank you for the new data (in bold).
You should need to replace the full oil charge.