I was charging my a/c system with Dura cool and put alittle too much in. When I was bleeding the excess off (slowly)I noticed alot of green dyed oil.
I have the pressure right at 35psi (suction) it cools ok but not Great.
I pulled a full 28" vacuum. I was wondering if previous owner put too much oil in. Can too much oil in system keep it from cooling like it should? Thanks, Ken

I'm thinking you are a bit undercharged at 35. Try going to 45, which will drop to about 42 as the x-valve cycles. This is what I am running on both the 300d and the 240d with duracool. Took 2 cans exactly on the 240, 2 and about a quarter on the 300d.

When you check the pressure is it done at idle or at a higher rpm?

the pressure I gave you is at an idle. At higher rpm it will drop to about 35-38 low side. At idle I have 42-45 low, 148-155 high. I have had good results with duracool in the few weeks I have used it. Started with it in a 64 t-bird and was so happy with the way it was working I converted both the MB's over to it. Noticed a big drop in the power hit when the A/C kicked on compared to the 134a that was in them.

The color you see in the oil is probably UV dye.

I have read that too much oil is not good for the compressor and it can indeed prevent it from cooling as well. A very experienced AC guy told me, however, that too much oil does not hurt anything as long as the system cools okay.

This guy has a large automotive A/C repair business and sells parts as well. That's all he does and is a very helpful person when I'm buying parts from him. He seemed to dispute much of what I have read and have been told regarding auto A/C.

For what it's worth,

Thank you. Your all very helpful. Ken

You are supposed to be checking your pressures with the engine turning about 1500rpm, not at idle. 35psi at 1500rpm is way too high and probably indicates an over-charge. In these systems you only need about 34oz of gas, and you ideally want 25psi low-side at 1500rpm. There is a direct correlation between pressure and cooling ability. Too high on the low side and it won't cool well, and too low (below 25psi) it won't cool either. Check out some of the automotive a/c webpages if you want to confirm what I am saying.

Good Luck,

Greg

Yes, www.aircondition.com then click on "straight to the board" and then scroll down.

Good luck,

This is a duracool system. The amount of gas at full charge is about 14oz. It is a very light gas, not anywhere close to the weight of r12 or r134. I got the coldest vent temps at the pressures I posted running at normal idle. Also when using duracool you can't go by the sight glass. It looks to be way undercharged, but if you push it to being a clear glass it is way overcharged.

Sounds like you're charging it according to vent temp and that's the right way to go IMHO. Once you change to an alternative or replacement refrigerant, the sight glass means nothing.

Good luck,

I just talked to Don at Dura-Cool. He said to charge to 35psi at 1500 RPM. I was charging to 35psi at idle. at 1500RPM it drops to 20psi. I was under charged. Thank again guys. Ken

I'm curious.... what are you guys going to do if your "Dura-cool" systems need to be discharged in order to service the compressor, expansion value of hoses at some point in the future?

All of these alternative R12 blends require dedicated seperate A/C service equipment. Do you have an A/C service shop that will service a "Dura-Cool" system? Around here nobody will touch a system unless its R12 or R134.

Tim

In the case of a seal failure the problem is solved. If it came down to removal there are a couple of ways to do it. First is to use a modified propane tank, pull a vacuum and suck the stuff out. This is the legal way as the feds see it. As I see it we have filled our systems with propane and isobutane. Neither is in anyway a harmful ozone destroying gas. People vent it all the time when they fire up a gas stove, gas grill, propane torch etc. Don't think my 12oz of gas is going to hurt anything so if it came down to it I would vent it.

Can the sight glass be used with an R-134a system?

I've got R-134 put in my 300D along with new O-rings and whatnot, and I'm thinking the system may be low...but my aux fan isn't working, so that may play a part...


Thanks!

__________________
2001 VW Jetta TDI, 5 speed, daily driver
1991 Ford F-350, work in progress
1984 Ford F-250 4x4, 6.9l turbo diesel, 5 speed manual
Previous oilburners: 1980 IH Scout, 1984 E-350, 1985 M-B 300D, 1979 M-B 300SD, 1983 M-B 300D
Spark-free since 1999

The Warden: Do not use the sightglass for anything. It is meaningless. When you fill an a/c system you need to fill it according to high and low side pressure, in conjuction with vent temps. It is impossible to accurately charge your system by looking at that sight glass - I would dare say this statement is true even for r-12.

Greg
300D