Okay, I am at a loss and so confused, I have had intermittent ac issues where the AC would not blow out cold air, more often then not. Sometimes it will others it won't, I thought maybe something was wrong with the r134a level's so I went out and bought one of these to check my high and low pressure, and to fill it if needed:

http://www.autozone.com/autozone/acc...er=436027_0_0_

Before I attach this and put it on, the car is off, and before it was turned off, the air was blowing non cold, as soon as I turn my car on with the attachment attached.....my air kicks on, and stays on very cold for at least 5 engine cycles (after I check my levels and they are at perfect levels, and detach tool, replace caps, and drive, then it stop's being cold.

Now if I reattach the tool, turn the engine on again, and let it run to test the level's it kicks back on.......using this tool for some reason kicks my ac into working, but when I stop using it, after a few cycles the air stops being cold?

Do you guys have any clue? Because I am stumped lol.

 

Do you have power at the AC clutch pin connector when vehicle running and ac on but not working? If so, the clutch is a little worn and you need to remove a shim.

How bout the pressure switch, any power there?

 

I don't have the proper tool to test it I don't think, but I did try to switch around matching relay's to see if it was the relay itself, with no luck, And i'm sorry, i'm pretty novice to most thing's under the hood, where is the pressure switch lol. I'm trying to fix it myself ot save a huge bill if it is simple.

 

You need a test light or a multimeter to test voltage. That will help you eliminate or pinpoint the problem. You can pick up either at a parts store or hardware store.

 

Okay, i'll get one later today, for future reference though, where is the pressure switch? And to test the AC Clutch relay, I just take the tool and touch it inside of that specific relay correct, and see if it is getting power.

Also, why would the ac kick into full power, and last for a few engine cycles after testing the pressure in the high and low valves?

 

No, remove the plug from the AC clutch and pressure switch, see if theres voltage at the terminals in the plug. If there is voltage and clutch not engaged, bingo. Do clutch first.

 

Ah, so we aren't talking about the relay's then? We are talking about the two plugs connected to the compressor itself correct? The key will have to be in the on position correct in the cab, but doesn't have to have the engine turned over?

And if there is power getting to the unit, through both connections, it mean's a shim will have to be removed correct?

What confuses me is why the AC kicks on and stays cold for a few engine cycles after testing the pressure level's lol.

 

Motor needs to be running for voltage to be present (later models), yes the plug on the compressor.

Lets just deal with the compressor for now, yes if voltage present clutch should be engaged, if it's not remove one shim. Also if voltage present, low pressure switch is fine, no need to check. It's located on top of the silver canister (accumulator) next to the radiator.

Recommend you download the factory service manual from the stickies on the main page, it's free, read the AC section, lots of good info in there, tell you exactly how to find your problem.

 

Okay weirdest thing, I ran one more high/low pressure test on the truck, and now all the sudden (knock on wood) the compressor clutch engages every time, and the air is ice cold. I have ran about 20ish turn over's with turning air on/off going from hot to cold, and each time it has gone to ice cold ^_^. Even driving the clutch stays engaged.

I am beginning to think that maybe the system was topped with a tad too much r134a, and it prevented the clutch from kicking on, even though the pressure gauges read perfect level's, maybe the r134a released from the pressure test's released the right amount of r134a to allow thew clutch to engage, because there was no high pressure?

 

What year is your truck?