My truck is new to me this year and when I bought it in Feb there was no R-134a freon in the system so I assumed that there may be a leak somewhere b/c the Previous owner claimed it worked. So I charged it back at the beginning of the summer with dye and all and it cooled and worked great.

My current problem:
About a week ago my compressor started cycling again as it does when the freon gets low so I just bought a can and thought I'd just add it and get another 2 months out of it. The Cheap-O gauge that comes with some cans read that it was normal low sided pressure so I didn't add it and today I put it on a real set of gauges. and when the compressor is on both the high and low side read where they should but the compressor still cycles.

My Question:
I'm not at A/C expert but I have a feeling that the sensor (that reads the freon pressures and tells the compressor to kick off when low) has gone out if there is such a thing or is this just the sign the compressor is on its way out?

Is there anything else that could be going on? (cheaper than the compressor)

I dread changing one b/c of its location is it a big job?

has anyone done it, Any pointers. is it expensive?

Any other ideas appreciated!

Thank you

JT

 

try changing the hi and low pressure switches one is on the accumulator the other is down by the comp on the tubing from comp next to intercooler pipe. they can be removed with no loss of R134 there on schrader valves.

 

Unless you have it on max it is common. if its cooling I wouldnt mess with it. If it is too low the low press switch will not let it come on.

 

Well I did some reading and learning about how the A/C compressor works and with the advice here I saw that R-134A High pressures should be 2.2-2.5x the ambient Temp and since it was 95-98F that afternoon it should have read between 210-245. it was reading ~150. The low side when I studied it closer it was dropping below 40 when the compressor engaged and rising to "static pressure" when it was off which I had backwards. Another issue I ran into. At 90-95F ambient temp the low side should read 50-55 (one table I found) and I find that with the auto-part store cans that its fighting an uphill battle to try to raise to even 45 psi b/c the pressure in the can isn't high enough!

I was able to add most of one can and the compressor quit cycling and blew steady cool air! from what the gauges are still saying its still low but its above the low-pressure so it stays on. If I were to try it on a cooler day I would be able to add a little more b/c the low-sided pressures wouldn't be as high and the store-bought cans can be drawn in better!

IT appears I do have a leak and I did fill with dye at the beginning of the summer but I don't see any OBVIOUS leak under the hood. I'm going to just keep adding $3.99 cans each month till the end of the summer and if I feel like it I'll tackle the A/C leak over the winter!

I've heard of the dread evaporator under the dash as being common to require replacing but I'll add more dye next month so I should have a good mark as to where the leak is coming from!

if it was a matter of replacing one part I'd be tempted to just do it now so I'd have the rest of the summer to know if it works and it was the correct part but my NAPA told me that for them to honor their compressor warranty I had to show I replaced a few other parts in the cooling system as well because they said if they were "bad" they could cause premature failure of a new compressor. The price starts rising pretty quick at that point!

When I have an ominous need for tires coming soon and a clutch if I ever want to add more power to it I'm trying to save from dumping a ton into it at this point!

 

50-55 on the low side is way high for 134, anything between 15 to 40 is good, after you added refrigerant what were your pressures?