New to playing with A/C systems. Which port do I hook up my can of 134A with a guage to check the A/C system?

I found a black cap on an A/C line on the passenger side and toward the front of the engine (is this the correct place)?

There also appears to be a port on the tin can looking thing up by the firewall.

Any help wld be appreciated.

97 F-150 XLT with 4.6 V8

 

That one. The other is the high side port that your adapter wouldn't fit anyway.

Take a static reading first to see if you even need a recharge. You need a minimum of 45 psi at your ambient temperature in order to "make" the cycling pressure switch and enable compressor clutch engagement.

Steve

 

The first one should be helpful - the 2nd might be too technical, and probably not useful for you anyway.

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Thanks guys. I will be out in the garage playing around tody.

 

Thanks again. Over 10 years of service on my 97 and the 134A level was up to where it should be. I love to tinker with things so I felt I just had to know which port to check.

 

Hey I just checked mine and it is right at 45-46, but my guage says that is full and not to add anymore, what do you think? Am I ok, should I add more, I don't want to overfill it by any means

 

Sounds like you have a POS low-side only guage.... It's like trying to listen to stereo music while being deaf in one ear.

Static pressure with 90F ambient underhood temp should be around 100-110 psi, not 45 or so.

You are substantially undercharged.

The low side guage reading is for while the compressor is operating...and it's still like being deaf in one ear since you will have no idea when the proper chrage lelvel is reached.

Steve

 

Thanks Steve, but I have a question, Since all I have is the low side guage, and it read 45-46 when the engine was on and the AC was on the max setting how much more do you recommend that I add? What PSI should I fill it to on my low side guage?

 

You cannot accurately charge a system with only a low-side gauge. I thought I made that clear. I cannot make ANY recommendation as to how much you need based solely on your single reading.

However, if you are reading the same value whether the A/C compressor is running or not and the reading is what you supplied, you are charged below the minimum required to even activate the compressor clutch.

If the compressor were cycling, you'd see the low side reading drop down to around 22-23 psi, the clutch would disengage, the low side pressure would rise back up to around 45 psi, and the cycle would repeat. The frequency of the cycle would be determined by several factors including the charge in the system, the ambient temperature, and the heat load being transferred. During more extreme conditions, it might never cycle (it would stay on constantly) and would still be normal.

Are you seeing any evidence that the compressor is engaging or not?

Steve

 

Check the o-rings in that gauge set.

 

Thanks for the information, I didn't know the compressor and clutch cycled like that. When I got my reading I just snapped the guage on and took it right back off, maybe I should put it on and watch it for a few minutes and see if it dips down, if the pressure dips down I guess the clutch is engauging therefore I must have enough coolant to at least keep the system going. If it just stays at the 45-46psi mark and never dips I might add a little because that will mean the clutch isn't engauging correct?

 

You can hear the clutch engage, the engine will change tone due to the load, and you'll see the front of the compressor start spinning.

 

I have the same question except for on a 1999 f-150 5.4L. Any help to locate the low pressure side port?

 

You'd better be wearing your fire-retardent suit because you're going to get flamed for asking a question I already answered IN THIS THREAD.