AC no cold air pressures measured insight please (1 Viewer)

[Biga27110]

Hey guys,

I no longer have front or rear ac but the compressor still kicks on. Rear ac never really cooled. I read as many posts on the forums as I could. I bought some guages and need help for the next step. First pic is max ac at idle showing 5psi low side. Second pic is at 2k rpm showing 0psi low side. Ambient is 75f. Im thinking I need to add r134a as my first step to see if it holds pressure, can't find any obvious leaks and see if I get cold air.

Compressor makes a little noise not sure as it's not significant and seems to work.

Sight glass shows some bubbles with AC on.

 

[AFei]

I'm also working on my AC and my share some experience. It may not be correct but you can try.

If this happen to my car, I'd suspect no enough R134A in the system. Did you check the glass sight and see if bubble there?
See the picture I attached in my thread: 2004 LX470: AC compressor not engaging with self diagnostic code 21 & 23

 

[Biga27110]

I'm also working on my AC and my share some experience. It may not be correct but you can try.

If this happen to my car, I'd suspect no enough R134A in the system. Did you check the glass sight and see if bubble there?
See the picture I attached in my thread: 2004 LX470: AC compressor not engaging with self diagnostic code 21 & 23

Ya there are bubbles.

 

[AFei]

So according to the FSM, there is no insufficient refrigerant if there is bubble. You can buy some R134A to recharge, better with UV dye for future leakage detection.

Since you won't be able to tell how much refrigerant to charge by weight, you may have to either check the pressure or use the glass sight:

As far as the right pressure at the low side, I really didn't figure out the right number. I heard it depends on lots of variable like air temperature, humidity, and so on.

This thread summaries the steps to recharge: No AC FAQ ?


Hopefully it helps and good luck!

 

[nissanh]

I go by the gas-slight glass located on the filter. I fill it until I see just a bubble or two. Keep windows open and AC on Max while adding refregerent.

 

[ramangain]

One can of this recharged my AC system for over a year now, all year use in FL too.

 

[BadReligion]

Refrigerant is not a consumable. If you are low, you have a leak. If you run your system low, you will eventually burn out your compressor....which upon failure will spew metal debris throughout your entire AC system. Locate the leak and fix it.

 

[Biga27110]

Refrigerant is not a consumable. If you are low, you have a leak. If you run your system low, you will eventually burn out your compressor....which upon failure will spew metal debris throughout your entire AC system. Locate the leak and fix it.

I need to recharge it to find the leak right?

Thats my current plan. Now that i see my pressures are low.

 

[BadReligion]

I need to recharge it to find the leak right?

Thats my current plan. Now that i see my pressures are low.

Yes. My comment was directed at those who just like to "recharge" their AC system yearly and call it good.

Recharge and see if pressure drops (which it will). Spend some time inspecting all of the lines and look for any oily residue. Sometimes the leak is at the front evaporator where it is hard to visually confirm a leak.

 

[Biga27110]

Yes. My comment was directed at those who just like to "recharge" their AC system yearly and call it good.

Recharge and see if pressure drops (which it will). Spend some time inspecting all of the lines and look for any oily residue. Sometimes the leak is at the front evaporator where it is hard to visually confirm a leak.

Thanks for the location tips. My car is a socal car there is no rust so im surprised a leak has formed somewhere. Strange thing is it has low side at 0-5psi but the compressor still kicks on. I thought there is a low pressure switch.

 

[Biga27110]

@flintknapper

 

[BadReligion]

@flintknapper

Good call. He knows AC systems very well and helped me rebuild mine.

 

[DTCsk8er]

I had a very slow leak I chased down for almost 2 years... leaked out a 12oz can ever few months. Tried dye several times, and never saw a single bit of dye anywhere on the lines/compressor, evap drain etc. I saw that Harbor Freight had a cheap refrigerant leak tester (sniffer), so gave it a go all over the truck. It threw a tiny bit of an alarm at one of the ports on the condenser, but it was intermittent at best. I replaced the o-ring on that line, as that was the easiest culprit.. pulled vac, and again it leaked out another can over several months. I finally ended up pulling the grill off, and spraying brake cleaner to clean out the condenser a bit so I could get a better look.. and while doing this, I saw a tiny jet of gas shoot out of a fin as the brake cleaner passed it. Again, no oil, no dye present. Put the leak detector right on this gas jet, and sure enough, a tiny leak was detected. Replaced the condenser, and I've been good for about 10 months.

My point is, these small leaks are a complete ass to find. Even with proper tools, it was luck that brought me to it. Either way, it is not normal to loose refrigerant, as it is a closed system.

That being said, it seems normal to have the compressor kick on (on these trucks) when the low side is very low (<10psi). Never seemed to have damaged my compressor, but as soon as the AC stopped blowing cold, I wouldn't even turn on the compressor anymore. Anytime the high side is around 100-150, the rear AC will definitely not blow cold at all.. below 100, you can then expect the front AC to not blow cold as well.

Normal gauge pressures for mine now are around 30-40 on the low, and >220 on the high side, depending on the day. I measured the cans weight, and used the factor spec for how much to put in.

 

[AFei]

Strange thing is it has low side at 0-5psi but the compressor still kicks on. I thought there is a low pressure switch.

Have you tried the self on-board diagnostic to see what code the AC system may throw?
It seems to me that FSM said the L side should have 28 psi for the pressure switch to turn on the compressor.

Compressor makes a little noise not sure as it's not significant and seems to work.

I couldn't recall if I can hear any special noise from compressor.

I need to recharge it to find the leak right?

As I mentioned in floor 4, I'd recommend to add some UV dye during recharge to assist the future leakage detection, if that's your plan.

I go by the gas-slight glass located on the filter. I fill it until I see just a bubble or two.

Just fully recharged the totally-leaked AC to factory spec of 1100g, and the Glass Sight doesn't have any bubble.

 

[jay3253]

When mine went it leaked out once a year for about three or four years. I took it to many places that couldn't find the leak. Then one spring it went down when I was refilling it so fast it sounded like a tire was going flat. Found the hard lines from front AC to back AC had rubbed through from the factory hold downs. The dealer wanted $1700 just for the lines. I took the old lines out cut about a foot off the ends and found a place that would make soft lines from my old parts. Haven't had a leak since and it's been over a year.

 

[Biga27110]

Will update when recharged with dye.

 

[flintknapper]

Will update when recharged with dye.

I don't know what to attribute the compressor running at low pressure to, except possibly a faulty Trinary Switch (pressure switch) or inaccurate low side gauge on your manifold set.

You can check your gauges by taking the 'static' pressure of your system (assuming there is some amount of liquid refrigerant present). With engine OFF and system cool...the two sides (low and high side) will try to 'equalize'. So you should see roughly the same pressure indicated on each gauge . For instance...if it were 75°F 'ambient' temp outside then both of your gauges should have a static pressure reading of about 78 psi. IF your low side gauge does not closely match that of the high side then we need to investigate why.

After determining that your manifold set is accurate, then yes...it wouldn't hurt to introduce some refrigerant (and dye) into the system for starters.

Let us know what you find and we will try to help.

Flint.

 

[Biga27110]

I don't know what to attribute the compressor running at low pressure to, except possibly a faulty Trinary Switch (pressure switch) or inaccurate low side gauge on your manifold set.

You can check your gauges by taking the 'static' pressure of your system (assuming there is some amount of liquid refrigerant present). With engine OFF and system cool...the two sides (low and high side) will try to 'equalize'. So you should see roughly the same pressure indicated on each gauge . For instance...if it were 75°F 'ambient' temp outside then both of your gauges should have a static pressure reading of about 78 psi. IF your low side gauge does not closely match that of the high side then we need to investigate why.

After determining that your manifold set is accurate, then yes...it wouldn't hurt to introduce some refrigerant (and dye) into the system for starters.

Let us know what you find and we will try to help.

Flint.

Cold engine never started after sitting over night. Engine off and connected to gauges here are the results. These are cheap Amazon gauges so accuracy is probably lacking.

 

[AFei]

You may cross reference the gauge on another car with good running AC to have an idea on how accurate it's . It looks we got the same gauge from Amazon, and I'm pretty confident it's relatively accurate and good enough for non-professional to use.

 

[AFei]

It made sense to me that your compressor should kick in as the pressure is 58 psi at the beginning. When the compressor got spin, you should have cold air, and the L side pressure may drop. Once the it's below the threshold of 28 psi, I guess the pressure switch may turn off the compressor at that point. Not sure, just guess.

Anyhow, at least you know more R134A is desired for now.