Automotive Air Conditioning Information Forum

Hello,

Hello,

2001 Lexus GS300

Bought this car recently and the AC wasn't working from the beginning. Decided to pull vaccum using a shops machine, which it held and also charged it per specification. My friend did it as a favor so i just left quickly due to the late night. The clutch engages and stays on however it does not blow cold. Based on what the gauges are showing, I am leaning towards a faulty AC compressor.

High Side - 100 Psi
Low Side - 56 psi
RPM - 650
Outside Temperature - 76 F

Please let me know your thoughts and opinions.

Thank you!

You may be correct.
The hi side pressure you give leans toward that.
However, you have done the testing at 650RPM.

We test auto AC by having the RPM at 1500-1800.
Repeat your testing at that RPM. A compressor does very little work, if any, at such a low RPM

Also, how many miles on the car? You are lucky if you can get more than 100K miles from a comp.
The system held vacuum, but can still leak under pressure. A leak check with a sniffer would be advisable. Pay particular attention to the comp shaft seal. To do this , put a shower cap around the comp overnight, then slip the probe of the sniffer inside the cap the next day

Hello!

Thank you for the response!

I ran outside and redid the test at 1500 RPM

The low side only dropped by 5psi and the high remained the same.

The car has 216,000 miles but the engine has 65k miles. It's a 2JZGTE VVTi JDM engine from a Toyota Aristo of same year. It's a direct swapped and the ac compressor are identical from the US non turbo engine to the Japanese one. The engine itself has over 65k miles.

I have never used a sniffer before. Do you have a reccomended brand?

Thank you!

tbirdtbird wrote: ↑Sat Apr 06, 2024 10:42 am You may be correct.
The hi side pressure you give leans toward that.
However, you have done the testing at 650RPM.

We test auto AC by having the RPM at 1500-1800.
Repeat your testing at that RPM. A compressor does very little work, if any, at such a low RPM

Also, how many miles on the car? You are lucky if you can get more than 100K miles from a comp.
The system held vacuum, but can still leak under pressure. A leak check with a sniffer would be advisable. Pay particular attention to the comp shaft seal. To do this , put a shower cap around the comp overnight, then slip the probe of the sniffer inside the cap the next day

Just to add, the pressures remain the same after the car is shut off. It's been one hour.

I think the comp is NG, assuming it actually has refrigerant still inside

what is your country

I think any sniffer from a so-called big box store would do for the random user

tbirdtbird wrote: ↑Sat Apr 06, 2024 1:18 pm I think the comp is NG, assuming it actually has refrigerant still inside

what is your country

I think any sniffer from a so-called big box store would do for the random user

It does still have refrigerant as it spits a bunch when I remove high Side line.

United States. I was just asking if there was a reccomended brand. Nothing cheapo that'll give me bad readings.

Appreciate the help!

tbirdtbird wrote: ↑Sat Apr 06, 2024 1:18 pm I think the comp is NG, assuming it actually has refrigerant still inside

what is your country

I think any sniffer from a so-called big box store would do for the random user

And just to clarify, the pressure reading do not change on the gauges after I shut it off. They remain the same ass 100 and 56 Does this have anything to do with the expansion valve or is this normal behavior?

After one hour, the HP and LP sides should equalize. If they don't, the cause is usually a defective metering device—in this instance, the TXV—and/or a blockage someplace.

Presuming a full charge of refrigerant, if you're seeing only 100 PSI on the high side at an ambient temperature of 76°F, it does appear that the compressor is worn out. A low-side reading of 56 PSI translates to an evaporator temperature of about 60°F, which explains no measurable cooling at the same ambient.

JohnHere wrote: ↑Sat Apr 06, 2024 3:51 pm After one hour, the HP and LP sides should equalize. If they don't, the cause is usually a defective metering device—in this instance, the TXV—and/or a blockage someplace.

Presuming a full charge of refrigerant, if you're seeing only 100 PSI on the high side at an ambient temperature of 76°F, it does appear that the compressor is worn out. A low-side reading of 56 PSI translates to an evaporator temperature of about 60°F, which explains no measurable cooling at the same ambient.

Appreciate the help! I will be ordering a TXV and an AC compressor. Probably even an evaporator core because I have to remove th3 dash to access the TXV anyways. Once again, thank you for your time and knowledge.

I believe your car has a variable-displacement compressor. If so, you could try replacing only the compressor's control valve first. But with that amount of mileage on the car, I too would go ahead and replace the entire compressor/clutch assembly.

I strongly recommend replacing both the condenser and R/D as well. (If you buy a new condenser, the R/D is integral with it.) In fact, most if not all manufacturers require condenser and R/D replacement, along with the new compressor, for warranty purposes.

Speaking of which, always go with a brand-new, not rebuilt compressor.

If you're going to replace the H-type TXV (Denso is the OEM for your car), try to get a Denso unit, if available, to ensure trouble-free performance.

The specs that I have for your car are as follows: 21-23.0 ounces net weight of R-134a, and 7.0 fluid ounces of PAG-46 oil. However, the under-hood decal takes precedence if different.

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