Lavrishevo

iTrader: (1)

So, on another topic. I just purchased a can of 134a with the gauge to check the AC system. It only test the low side. From what I understand, the low side should be between 22 - 26 psi on my 99. I am getting between 45 - 55 psi at the low side. I don't have a high side tester.

The AC is cool but not as cold I would like it. Something is not right here is it? Can a leak cause the low side to be too high? Not sure how this all works but would love some advice. Trying to avoid too much cost from a shop or dealer if I can fix it myself. Should I be worried that the low side is that high in pressure?

Lavrishevo

iTrader: (1)

Alright now I am even more confused. The can says at 85 degree temperature the low side should between 45 and 55 PSI. So I follow the procedure again. Let her idle for 3 min with AC on high and was sitting right at 45. When I added freon the pressure actually went down and then back up to 40 - 45. Lol. I have no clue what's up.

timmy0tool

iTrader: (7)

when you add freon the pressure fluctuates depending on the piercing valve's position. this is normal from my experience, just don't over pressurize it.

i know there are other AC techs here that will chime in and tell you the proper way, and it's not with a can of 134a from the auto store.

LScowboyLS

unfortunately, one of the things that makes A/C difficult is that there is no "dipstick" and no certain pressure that is correct on the low or high side pressure, due to many variables such as temperature, fan clutch condition (on fan clutch equipped models) condenser condition, evaporator condition, whether the expansion valve is at its stock setting and many other factors.

the only definitive way to know if you have the correct about of refrigerant in a vehicle, is to evacuate the system and weigh in the correct factory charge - any other way is a guess

my favorite "easy" way is to watch the sight glass which is located in the top of the dryer, a silvery aluminum can about the size of a can of Red Bull in front of the condenser (what most folks mistakenly think is the radiator) drivers side down below battery and charge until you no longer see any bubbles in the refrigerant when viewed peering down in the sight glass - clean sight glass with alcohol soaked wash cloth and use a flashlight for better viewing of bubbles, and be patient, bubbles can take a while to cycle around to the point in the system (high side) that you are viewing. (as much as 3 or 4 minutes)

Lavrishevo

iTrader: (1)

OK, I did confuse myself a bit. 22 - 26 is amount of oz of freon in the system. Not the low pressure side. I really need to get a reading on my high pressure side. I went ahead and put the whole can in as as the pressure actually dropped as I was putting freon in. I am guessing the freon help push some air out something. It was an 18 oz can too. The pressure dropped as I was adding freon so logically I think it is not over pressurized. The AC does feel colder and after a 15 mile drive home I put her in park, ac on coldest and the pressure if fluctuating between 30 and 35. Which seems low now as the temp outside was 89 at that point.

Lavrishevo

iTrader: (1)

Yeah, I was looking at that sight glass at the high pressure side. I was seeing bubbles before I added freon.

LScowboyLS

I edited my instructions - refresh page and reread

Lavrishevo

iTrader: (1)

Just ran her for 5 min and no more bubbles in the window. Before, it was constant bubbles. Had no clue that was the way it was supposed to be.

Lavrishevo

iTrader: (1)

I am hearing a swooshing sound from inside the car. I can only hear it with the fan on low from inside the car with it parked. Turning the recirculate on and off does not affect it. It's almost like I am hearing the condenser or something. Kind of like a whoosh sound and then nothing but the fan, then whoosh again. I first thought it was the compressor turning on and off but it is not disengaging when I hear this sound (it does have a clutch). I'm also staying right around 30 - 35 psi on the low side which still makes me think it might be low on freon because everything I have read says I should be around 45-55 with the ambient temperature hitting 90 degree's. Anyone else hear this in their LS?

LScowboyLS

if the refrigerant is low, you will eventually see bubbles in the sight glass, though it could take 5 minutes or watching patiently for them to cycle around, you can also have a friend rev the motor a bit during that time and see if any appear

you should never have bubbles in the sight glass, but don't overfill it either, especially without a high side pressure reading, as this will lose the cooling you are trying to achieve and could even overheat the car and/or prematurely wear the compressor though

fortunately, another cool thing about the LS400 is, not only do we have the most reliable transmission and engine ever made, but also the most reliable A/C compressor, the legendary NipponDenso 10PA20C