This is my first time ever working on an A/C system and so I could definitely use some help.

I bought this truck (2003 2.3L Ranger) about 1.5 years ago but have never needed to use the A/C in it. However this year was the first time it got hot enough to need it. When using the A/C I notice the pump cycles very frequently. About every 5 seconds or so. The electric fan kicks on when the A/C is in use so I know that's good.

I bought a set of R134a gauges and just hooked them up this morning. I let the A/C run for a few minutes and then took my readings. Here's what I'm getting and it's confusing me.

Outside temp = 63*F

Low side: 60psi no pump - 80psi with pump
High side: 65psi no pump - 85psi with pump

Vent temp was 38*F.

no pump = compressor turns off
with pump = compressor kicks on

I was completely expecting the low side to be really low and the high side to be really high but it's the complete opposite. I don't know if this means that, yes, I am low on refrigerant or the system actually has a problem.

By the way, I'm not sure if this is normal but when I was evacuating my gauges a crap ton of this neon yellow oily stuff came out. And man does it stink. Washed my hands really good and they still stink like this stuff.

I sure could use some help. Thanks!

 

Too cool for effective troubleshooting. Wait for an 80+ day.

Those readings are essentially the same given some margin for error. Your gauge readings indicate that you are cross-circuiting in the manifold, probably because both valves are not closed (user error) or there are defective seals in the manifold (defective manifold).
A "short-cycling" compressor clutch is almost always caused by low refrigerant charge.

You will likely find both sides are going to be "low" once you resolve the issue with the manifold.

Leak detector dye. Shine a UV light on it and it will glow.

 

Thanks projectSHO89. That helped me immensely.

Chalk this up to user error and a learning experience. The manifold gauge set I have has two valves on each side; one up on the manifold and one down at the orifice. This time around I only opened the valve at the low side and high side orifice and left closed the valves on the manifold. I took a new reading and got the expected values:

65* ambient
Low side - 20psi compressor on - 37psi compressor off
High side - 70psi compressor on - 105psi compressor off

If I understand those readings correctly, they indicate that it is low on refrigerant.

 

Well, it sucked down 1 small can of refrigerant (only bought one) and apparently it needs more. Compressor will run and while it does, if I raise the idle to 2000 rpm the low side needle drops from 35 slowly down to 20 and then the compressor kicks off. High side jumps up to around 150 now before the compressor kicks off. If I just let the engine idle the low side gauge hovers around 21-22 psi and high side around 145'ish.

Ambient temp was 74*F.

If the system were properly charged the low side needle would be more stable correct?

 

Did you vacuum the system before you started putting more r134 in? Overfilled systems will cycle on and off like that too.

A sealed a/c system is in a vacuum state, so overfilling it is very easy to do. If it is overfilled, it will cycle on and off same as under filled and can burn out your compressor and burst seals.

 

Actually I didn't vacuum it down.

I had just assumed that a system that was overfilled would have had a lot higher pressures.

I will say that before I put the can in, the compressor would kick on and off frequently at idle (like every 5 seconds or so). But now, after the can, the compressor runs much longer at idle. I didn't time it but I'd say at least a minute.

 

Ok, if you opened the system, like when R134 sprayed on you and smells bad, you have lost vacuum and may have gotten air in the system, both things you don't want to do. I can tell you the Easiest, fastest, most straight forward way to do it.

 

First, go to AutoZone or O'reillys and rent a vacuum pump. If you have never rented a tool it is very easy. You ask to rent it, they make you pay the full amount and when you bring it back, they refund your money. Check the vacuum pump in the store at the counter before you leave. Take it out of the box, and check the oil level. If it is not at the line, make them add oil to the line. There is no need to buy oil as long as you leave with it at the line.

 

Heres the short version because I am leaving, I will come back.

1)Vacuum the system for 30 minutes.

2) shut off pump and see if the system holds vac for 15-30 minutes.

3) if if it does, fill the system with 30 ounces of R134 and you are done.

There really isnt a need to understand the manifold gauges unless you have a leak or a component failure. You can cause a component failure by having more or less than 30 ounces in the system.

 

Cool! Thanks Jklnhyd.

Yeah, I've rented tools before from Auto Zone. I'll hit up A.Z. tomorrow and see if they have a vacuum pump to rent.

For refrigerant I figure I don't need anything special right? Just 30oz of the normal stuff?

Oh, quick question: When pulling a vacuum do I do that from the low side?

 

You have the manifold hooked up to the high and low, but they are closed at the manifold. Open them up at the ports. Then hook up the vacuum and turn it on. After it starts running, you will open the high and low at the manifold.

Let it run for 1 hour.

BEFORE turning off the vacuum, close the high and low valves on the manifold. Then turn off the vacuum.

The high pressure gauge will read zero, you dont care about that. The low pressure gauge will be below zero, showing a vacuumed state in hg. You can googled what hg it should be at, iirc it has to do with sea level, but that really doesnt matter. You just want to see what it is, and make sure it is the same after 30 minutes.

If it is the same after 30 minutes, your system is sealed tight, you are happy.

If it has dropped, or you think it mighta coulda, wait another 30 to confirm it. If it has obviously dropped, then you have to find the leak. I doubt your system has a leak if it was taken r134 before and cycling at all. So you should be fine.
If for ANY reason, you accidently open the system, reevac it using the pump. You need the system under a vacuum.

Since the system is under vacuum, it will suck in the R134. It is easy now because you need 30 ounces, should be 2.5 cans, right? So dont follow the instructions on the can that says 12 oclock to 3 oclock. Simply invert the can, bottom up, and shake it and the vacuum that you now, created, will suck it in. Repeat that with the second can. The third can, you can watch your filler gauge and get it between the arrows.

You will still have vacuum in the system, which is how the R134 is able to compress and expand. No vacuum, and it can't.

Buy the cheapest r134 that you can. It is federally regulated so r134 is r134, there is no superior contentration, lol.

Now you know exactly how much r134 is in your system, not guessing.

There is a question of oil and if you should add it. I did the first time I did this on my own, and burned up a compressor and then again with a $400 replacement compressor, and havent added any since.

Oh, and here is the site that I used to get your refrigerant capacity.
http://www.techchoiceparts.com/refri...rd-light-truck

 

Wow, thanks Jklnhyd. I really appreciate the info.

One more question; Do I need to discharge the system of refrigerant prior to pulling a vacuum on it or will the pump evacuate the refrigerant for me?

 

The vacuum pump is discharging the system. And of course you are containing the evacuated r134 in a proper container because although it is environmentally safe, it may be against the law to vent it into the atmosphere like I allegedly did.

 

Thanks again. Oh and yes, I will be collecting it in an approved container.

 

No need to pull a vacuum here. I don't see where the OP said he opened the system up and let air in. He just said he's low on refrigerant. In that case, just add more refrigerant. However, if you're low on refrigerant, you have a leak. You should find and fix the leak first, otherwise that refrigerant is just gonna leak right back out again.