Hi all.
My 92 shorty 3.0 A/C system is currently using Duracool and I seem to have an issue with the compressor not cycling like it should. The compressor engages as soon as the switch is turned on but at idle it never turns off and the system doesnt cool down much at all.
If I drive on the highway, the system does get cool and I can feel the compressor cycling as it should.
In my experience with undercharged systems, the compressor cycles too frequently, opposite to my condition.
Any ideas?

 

well, that should lead to the likely conclusion that it's overcharged or contaminated....

have you take low and high side pressure readings?

Under certain conditions, it's perfectly normal for the compressor to NOT cycle.

Steve

 

has it ran correctly on your R134a replacement before the troubles?

1 oz. of Duracool is equivalent to 2.5 ozs of R134a.
did you overcharge?

impossible to completely evacuate a dual a/c Aero system F&R without using a motor driven vacuum pump.

 

Unfortunatly aero has no climat controll that stops AC depending on air temperature. Ac is off when pressure too high ore WOT relay is actuated....

 

Duracool is not legal in the USA for use in mobil applications such as motor vehicles. Use R-134a instead. Duracool is dangerously flammable when used in motor vehicles and is made from a blend of hydrocarbons. Properly completed R-134a conversiosn work just fine. Based upon your desription of your problem, you have something more going on which may require the replacement of parts. However, it is almost impossible to diagnose your problem without a manifold gauge set and a thermometer.

 

I checked the pressure on the low side at idle with compressor engaged and it was way too high. I bled off some refrigerant until it was within spec (30-38 lbs according to Duracool) and it stopped cooling entirely. I then reved the engine to about 3000 rpm and the compressor began cycling very quickly, it would stay on for around 1.5 seconds then turn off again kind of like it was undercharged. I also noticed that when it was working marginally (before I did the bleed off) the pipe leading into the receiver drier tank would get cool but as soon as I turned off the compressor (by pulling off the electrical connector) the pipe would get hot right away, almost too hot to hold. Is this normal?
The A/C worked well at the start of summer then quit rather abruptly so there is definately somthing amiss here. Wife is not happy and you know what they say ... "Happy wife happy life". That being said, I have to fix it ASAP! Given the new info, does anyone have any ideas?

 

how expensive is R134a in Canada.
EPA is about to take it off market here because of environmental concerns. they have to find a reasonable efficient safe replacement first.

 

I had a similar scenario once where the system cooled down when I was at higher speeds on the highway. Would not cool when idling or driving slowly. Checked the discharge and suction pressure with a manifold gage set. Low discharge and high suction at low speed, no cooling. I then revved the engine from under the hood and both suction and discharge got a lot better. It turned out to be a bad compressor. I tore down the old compressor to see exactly what the problem was. The vanes which do the compressing of the gas, inside the unit, were made to slide outward by centrifugal force. Each vane had a rough spot on it. At low speed, low centrifugal force, the rough spot kept the vanes from moving/sliding properly. High speed, high cent force and the vanes moved as they should, overcoming the rough area. The vanes fit in a very close tolerance slot that must stay well oiled. I must have had an oil problem that started the whole issue. Changed the compressor and it works fine. I examined the entire system for debris and it was clean, very thankfully. This was about 2 years ago, still OK. You may have a similar problem.

 

Thanks. I expect that you could be correct, the compressor has been a little noisy and last year I replaced the condenser, receiver drier / liquid tank and the main tube off the back of the compressor all without adding oil.
I will price out a compressor today. Any tips on cleaning the system to make sure theres no debris that might clog things up?

 

Ok, to clean up the system, you will need a flushing tank, an air compressor to operate it (at least a 5 gallon air compressor), and a good flushing fluid.

You will need to remove all the hoses from the system. Flush the hoses individually. You also need to flush the condensor and evaporator, which you can do in the vehicle. Be sure you remove the orfice tube before trying to flush the evaporator.

The parts you need to replace are the orfice tube, accumulator, and all seals that you encounter.

 

Without a manifold gauge set, you still don't have any diagnosis. That means you're just guessing.

Get the gauges on there so you can see what is actually happening.

Noisy compressors are often caused by an improper charge. Why waste money on parts when you don't even know yet what is wrong?

 

Good advice and I agree completely. I have a set of guages but I just dont know how to read or interprit the pressures, What should I look for, what RPM should the motor be running at when I read the pressures?

 

Doesn't matter what RPM, you are looking for pressure relationships, and the behavior of the needle when the compressor is on, right as it turns off, and stuff like that. In a properly operating system with the compressor running, the low side pressure should be between 35 - 75 psi (depending on temperature), and the high side should be in the range indicated on the gauge. The needle should change with the compressor cycling, the high should stay high, while the low fluctuates with cabin temperature and the compressor. I know I'm being a little vague, I don't have the actual specs in front of me. If the high side is really high, then the high side is restricted, if the pressures are about the same, then the compressor is most likely bad, either because it cannot hold pressure do to internal leaks, or because the clutch may be slipping. There a lot of factors, but the pressure ranges are often indicated on the gauges. If both gauges are working in the correct ranges with the system running, then chances are possibly realted to something else, like bebris blocking airflow thought eh heater core, a bad blend door, or too many bugs plastered on the condensor. If the pressures are outside the desired range, or the needle bounces wildly, then there is a problem with a component in the cooling system.

Tell you what, let us know what kind of readings you are getting with the compressor on, with it of, and how the needle behaves as the compressor cycles.

 

Tried to hook up the guages but discovered that the high pressure fitting wouldent fit the guage set, will try to find an adapter tomorrow.
When some gas escaped while "trying" to fit the guage set onto the high pressure tube, black oil came out. Somehow that doesnt sound like a good sign?

 

an FX15 compressor Black Death
the teflon rings turned into mush

Aircondition.Com - What is Black Death?

suggest using only FX15 spec'd a/c coolants and compatible lubes.