Recharging A/C after compressor/filter replacement.

[mattd1979]

How many cans are necessary to recharge the A/C system in a 1990 Q45?

[Infinitiguy19]

R12 or R134a?

[qship96]

should be professionally evacuated to boil off all moisture and refilled to exact weight specced in manual - forget "cans"

[mattd1979]

It is using all of the r12 components with the r-134a high and low side fittings. I did the conversion right after I bought the car back in 2006 when I replaced the compressor the first time.

[mattd1979]

My uncle is helping me with it. He is a retired a/c man. We have a vacuum pump but just don't have the scale. I did this back in 2006 and it has worked well until the compressor went bad.

[qship96]

Well you could look in the service manual for freon weight in ounces, but since you converted to r134 the amount may be different as compared to r12. Your uncle should know how to get it close and dial it in by pressure and vent temps{ but the best way is by weight if using the refrigerant the system was specced for}

[mattd1979]

Yeah. I know. I just wanted to know how many cans I will need. My spending is a little tight right now so trying to avoid spending more then necessary.

[qship96]

The later 94-96Q that originally came stock with r134 held about 27 ounces of r134 if I recall- so maybe get 3 12 oz cans to be sure you have a little more on hand than you actually need

[Q451990]

Sounds about right. I always buy more than I need and then return the unused portion. It makes it much easier than stopping half way through the process to run to the store to get more if you need it...

Heath

[mattd1979]

I am going to have to add oil to the compressor before I install it. I was reading the specs in the service manual and they seem a bit confusing. First off it says that prior to opening up the system for repairs, the system must be stabilized for correct oil replenishment. Here are the steps for "Oil-return" operation..

1. Set a manifold gauge in position.2. Start engine and set engine speed and air conditioning system as follows: Test conditions: Engine speed: 1,000 - 1,500 rpm AUTO switch: "ON" Blower speed: 4-speed Intake: REC

3. High pressure is regulated to stabilize oil distribution with compressor held at full-stroke length.

High side pressure gauge must register at least 85 psi.

4. Conduct the "oil-return" operation for approximately 10 minutes.5. Stop engine.

Oil level check

1. After the "oil-return" operation, remove compressor from vehicle.2. Measure compressor oil level.3. Check test results. Total oil quantity in system: 8.0 fl oz Oil returned to compressor from system: 3.2 fl oz (For reference) Oil left in compressor (service part): 8.0 fl oz

The above measurements to me seem a bit confusing. If the total system capacity for oil is 8 oz, how can there be 8 oz left in the compressor?

Also, why is the above operation called "oil-return"? Return to where?

Matt


Modified by mattd1979 at 12:20 AM 4/11/2010

[qship96]

Infiniti brand new or rebuilt compressors come with 7-8 ounces of NEW oil already installed in the compressor. When you get the new compressor, drain this oil out and save it in a clean container marked in ounces.

Take old compressor off of car and drain the old oil out into a container marked in ounces, note how many ounces came out and put this exact amount of NEW OIL plus 1 extra ounce{to make up for the 1 ounce of oil trapped in old dryer you are replacing} back into the NEW compressor and install compressor on car.

The above assumes that the cars a/c system contained the correct amount of oil before you started the entire procedure, which is next to impossible to be sure of if you have had massive leaks or untrained people along the way mess with the system.The only way to "start from fresh" is to disconnect everything and flush out all oil from condensor,evaporator, lines, then add the 8 ounce charge along with new dryer and compressor.....a huge job.

[mattd1979]

I replaced the compressor yesterday and I added 2.3 oz of PAG-100 R-134a compressor oil in the compressor. I also replaced the filter of course. My uncle came over and hooked up the vacuum pump and pulled a vacuum for an hour. We let it sit for about 10 minutes and the vacuum held. He then added all 3 cans with no problem. I read later on that it was best to use Ester oil. Will this cause a problem? I believe the oil that was put in the system almost 4 years ago was also PAG oil.

[qship96]

Did you purchase a new, rebuilt, or used compressor? Brand? how is the cooling performance and vent temps?

[mattd1979]

The compressor is a rebuilt unit. It is working fine. Today it was around 94 in the car and it didn't take hardly anytime before it was comfortable. I was just wondering if the oil that I used will be OK.

[Drake57]

Matt, I wouldn't worry. What are you going to do what sounds like limited facilities? Vent some refrigerant? 99.9 % of compressors new and rebuilt today come w oil, any reputable supplier will tell you type and quantity of oil in compressor.

Ester is more compatible w mineral oil than is PAG, but unless you remove evap, flush and remove all oil from evap & condenser, replace dryer, you are only guessing at oil qty remaining in system. I don't know about ester/PAG compatibility.

So given that you are DIY (and don't get me wrong, I believe in DIY) with apparently limited facilities, what's done is done, and unless you're prepared to do a complete flush, purge, and evacuation, if you are getting good results, I wouldn't worry too much.

You may want to write down date, qty and type oil and refrigerant used, etc., so that if you have to go through it again, you will have records. Most shops doing r12 to r134a conversions record such on a label.

[mattd1979]

Yeah, the re-manufactured compressor came dry. It said that I would need to add oil to it. When I replaced the last compressor about 4 years ago, I did all that you mentioned. I removed the evap and the condenser along with all of the lines and used about 3 to 4 cans of this highly evaporative cleaner to flush the system before I installed the reman compressor, new filter, and expansion valve. I just wasn't sure what oil I used. I seem to think that it was PAG before because when I bought the oil the other day, the name looked familiar. I am going to open up the old compressor to see what exactly went wrong with it.

Matt

[Garceaud]

Service manual calls for 40 - 44oz if your starting with an empty system. 90-93