AC help please! So hot. I need proper pressures.

[immajackuup]

Final system pressures idle @110-115ish ambient temps in the garage.

you're killing the compressor just to let you know.

[agent]

What is reccomended for a conversion such as this is ester oil.

I was given that same info by two separate people (bimmerteck being one of them) and used ester in mine.

[scottinAZ]

Small amounts of oil leave the compressor with refrigerant and circulate through the system while the majority sits in the compressor. A good flush should have removed residual oil from the system. Since you're concerned with oil mixing and ran the compressor with both oils present, you really should drain the compressor and refill with the prescribed quantity of PAG.



Correct. And if you really want to get anal in this situation, you'd pump the system down and dump the oil a couple more times after running it to minimize the presence of old oil.

What is reccomended for a conversion such as this is ester oil. will not react with the residual oil left in the system (no way to get it truly all out) the way that PAG and mineral will (totally unmiscable, so can cause issues with lack of lube)

[bben76]

Think I'll pull the compressor and let it drain overnight just be sure.

In the interest of doing everything right this time do you think it matters that I flushed the evap backwards? It was easier for me to run flush agent and compressed air through in reverse direction of what freon runs through it b/c I couldn't get the end of the air compressor and blow nozzle under the dash. I can't see why this would matter but just thought I'd throw it out there for comment. I ran it through until it until it ran clear.

[Ryann]

Should I assume that the oil that has been put in is all still there even though I've flushed the system? Does the oil circulate or only remain in the compressor?

Small amounts of oil leave the compressor with refrigerant and circulate through the system while the majority sits in the compressor. A good flush should have removed residual oil from the system. Since you're concerned with oil mixing and ran the compressor with both oils present, you really should drain the compressor and refill with the prescribed quantity of PAG.

But if it's got mineral oil in it, last I checked PAG is not compatible. Correct?

Correct. And if you really want to get anal in this situation, you'd pump the system down and dump the oil a couple more times after running it to minimize the presence of old oil.

[nrubenstein]

(bben)I see. Props to you though for tackling it yourself.



If you'd like to drain the compressor you can remove it from the car and tip it over into a container, most of the oil will pour out of the suction port. Measure what comes out and replace with the same quantity of PAG and you're good to go.

But if it's got mineral oil in it, last I checked PAG is not compatible. Correct?

[bben76]

Ryann: ok thanks for the info on draining. I think I might just leave it as is. If I don't drain it do I need to put any oil back in when I charge the system? Should I assume that the oil that has been put in is all still there even though I've flushed the system? Does the oil circulate or only remain in the compressor?

[Ryann]

(bben)I see. Props to you though for tackling it yourself.

My only concern is about the gunk that might be leftover in the compressor because I don't know how to drain it.

If you'd like to drain the compressor you can remove it from the car and tip it over into a container, most of the oil will pour out of the suction port. Measure what comes out and replace with the same quantity of PAG and you're good to go.

[agent]

Just finished a friends car in Nashville this morning. The heat/humidity was brutal but system's all happy now.

[bben76]

Ryann, when I started I didn't know I needed to flush the system, I only had it evac'd. I charged it up only to discover the compressor was locked up (I had left the original compressor on). So, I replaced the compressor with a rebuilt one but this time didn't have it evac'd b/c I had just had it done previously - a complete noob at a/c. I guess I didn't understand fully what vacuuming did.

Admitting my lame-ass mistakes here so hopefully to assist other noobs who rush in.

I've got everything flushed now, my new receiver/drier arrives Tues. Try to do it right this time, I'll vac it down and hopefully now that the system is clean I'll have good luck. My only concern is about the gunk that might be leftover in the compressor because I don't know how to drain it.

[Ryann]

Still learning the gauges, trying to interpret what they mean.

Now I'm waiting on a new receiver/drier and will pull a vacuum and recharge and see what happens.

What's going on here? You flushed the system and then turned it on before evac. and recharge?

Either switching out to a higher CFM aux fan or swapping to a higher speed resistor on the stock aux. fan brings the head pressure right into line at around 240-250.

Agreed. even at 100F+ ambient 300 psi is too high for 134a imo.

[bben76]

Another tip, Napa has a big catalog of a/c repair parts and tools: www.napaonline.com

[bimmerteck]

Just finished a friends car in Nashville this morning. The heat/humidity was brutal but system's all happy now. Entire system was evacuated with a 5 cfm pump for 1 hour, lines on my guages were pre-charged with r134a so no atmospheric air was introduced to into the system. For those wondering about the high head pressure it's not overfilled(look at the suction). This is why I install lower resistance fan resistors in many of the cars I've converted around here. The high humidity combined with the heat kills efficiency and runs the high side slightly north of my preferred < 2.5x ambient. Either switching out to a higher CFM aux fan or swapping to a higher speed resistor on the stock aux. fan brings the head pressure right into line at around 240-250.

Vent temp when car was pulled in


Vent temp after charging, fan speed 2, recirc engaged 100+ ambient, RH=60%


BMW OBC registering 41.5 degrees Celsius (106.7 F)


Final system pressures idle @110-115ish ambient temps in the garage.

[bben76]

Got all the lines flushed and the evaporator and condensor. The A/C Pro flush seemed to clear out a lot of gunk, I watched as the fluid drained as I compressed air through and I saw it turn from dirty to clear ...most of the effluent was a dirty gold color. I feel like I got everything clean, but the directions said not to flush the compressor - is there a way to drain it or flush it?

Before starting today I took a static pressure reading and a reading while running just for reference. Here are what I had....

Static:


While engine running with a/c on (car was only running for 5 mins):



Still learning the gauges, trying to interpret what they mean.

Now I'm waiting on a new receiver/drier and will pull a vacuum and recharge and see what happens.

Whew! There seems to be a lot of mis-information and conflicting theories/opinions on e30 A/C ...for example check out the Pelican Parts thread (http://www.pelicanparts.com/bmw/tech...Recharging.htm) and the e30tech forum (http://www.e30tech.com/forum/showthread.php?t=58110) thread ...I'm leaning towards Ryann's info and advice in all areas - appears to be better grounded in science and experience than these. This is why r3vlimited is the bomb dot com.

[mistertonylee]

The cheap vac worked well for me. I was able to pull -1 atm for half an hour with no problem.