Compressor Cycles With Correct Amount of Freon

[sean9721]

Last week I finally decided to fix the a/c in my Ranger. I replaced the orifice tube and charged it up. I have a little less than 1lb 9oz of freon in it. When I rev it up to 2,000rpm, the compressor will cycle every 5 - 10 seconds, like it's low on freon. At idle the low pressure was about 47. At idle, the high pressure was about 250. To me, those pressures are a little too high. But if I take any freon out, it will cycle more. When I rev up to 2,000rpm, the low pressure drops pretty quickly. The air blowing out of the vents is decently cool. Water is dripping from the evaporator. The lines coming out of the accumulator are barely cool when I touch them.

When I replaced the orifice tube, there was a decent amount of metal shavings in it. I am leaning towards a bad compressor. The low pressure switch is causing the compressor to cycle. It cuts off at 25. I can jump the low pressure switch and it won't cycle every 5 - 10 seconds.

I do a/c work on ambulances so I somewhat know how a system works. The pressure readings from my truck really have me confused.

 

[TimR]

was the orifice tube the only replacement? How long was the system inoperative/open to atmosphere?

 

[sean9721]

Yea all I replaced was the orifice tube, and a busted o-ring. When I replaced the orifice tube, a good bit of oil came out that was a brownish color (which tells me rust). I didn't use the system for about 2 - 3 years before last week.

What do you mean "open to the atmosphere?" All the lines were connected while I wasn't using it.

 

[TimR]

you need to flush the system, and add a new accumulator / dryer. as to open, the amount of water indicates high humidity. While open, or inactive with a bad o-ring, the dryer will try to do it's job, and remove moisture, and become contaminated.

 

[sean9721]

Thanks for the advice. I'll replace the accumulator and see what happens.

 

[killj0y]

Yea this is the reason most autoparts stores wont warranty compressors unless you get a new orifice and dryer at the same time and change them out in sets. Also don't forget to vacuum the system when the dryer and everything else gets changed. Moisture in the system could be causing the refrigerant to not be able to compress properly.

 

[v8318cid]

Ok, a couple of things to consider here. First, metal shavings are never a good sign. Chunks would be worse, but you're losing material somewhere, most likely the compressor as you indicated. However, if you're getting head pressures of 250 psi or so (assuming max fan/blower speed at the time), your compressor is still functional. As for 47 psi suction, that isn't unusual if the outside temp is high (say, around 90F or higher). Revving the engine higher increases the compressor's suction pressure which will cause faster cycling times, although 5-10 seconds does seem a little faster than normal. It is possible that you have a restriction somewhere, albeit a small one. Still, I would not recommend leaving the pressure switch bypassed for an length of time. If you aren't already aware, bypassing the switch will eventually lead the system to pull into a vacuum on the low side, resulting in oil starvation and eventually a grenaded compressor. Then all you can do is replace the entire system (only guarantee the system will be free of debris).
Second, condensation on the lines is a fair indicator that the system is working, even if not at peak efficiency. If you haven't vacuumed the system out prior to charging, this could explain why the accumulator lines don't seem as cold as they should be.
I would advise you to use some sort of temperature gauge to see where the outlet temps are. If you're getting to or below 50F and are using a regular fixed orifice tube, you are probably doing ok.
Last, if you open the system again, I would strongly advise you to switch to a variable orifice tube. They work significantly better than the traditional fixed orifice tube at idle, at the expense of maybe a degree or two at road speed. A little more expensive, but worth the investment, in my opinion.

 

[sean9721]

I've never seen a system have the low pressure drop as fast as mine, which had me thinking something is up. I only jumped the low pressure switch to see if the cycling stopped, which it did. Before I charged the system, I had ran a 20 minute vacuum. The vents inside were putting out 47 when revving and then 60 something at idle.

I'm gonna replace the accumulator, and then go from there.

 

[sean9721]

Replaced the accumulator today. The compressor still clicks every 5 - 10 seconds. Low pressure at idle was 40. High pressure was 225. The air did seem a little colder on the way home. When I got home, I noticed a decent amount of moisture on the lines coming from the accumulator. The next step I'm gonna take is flushing everything. I checked the orifice tube and it was clear.

 

[killj0y]

Strange you have basically eliminated most of the common problems, besides a flush i suppose the only other culprit could be the compressor or condenser.

 

[TimR]

replace the low pressure switch. you shouldn't have to lose the freon to replace it, as it should have a shrader valve behind it.

 

[BRUTUS_T_HOG]

you need to replace the compressor, condenser, accumulator, orifice tube, and then flush the lines.

you should have stopped when you saw metal shavings.

250 is a bit high on the high side and indicates lack of airflow across the condenser or a plugged orifice tube

 

[sean9721]

Flushed everything out today. Charged to 1.38lbs. Low pressure was 45 and high was 230 at idle. No more cycling going down the road. The lines by the accumulator and the one going into the compressor get nice and cold.

 

[killj0y]

Woot Solved!