Land Cruiser 2001 Model GXR, AC Low Suction Line Pressure

[JohnHere]

I have checked again with the engine at 1800 rpm with the doors open and fan on high speed, I got the following :
Low Side Pressure : 25
High Side Pressure : 380
Vent Temperature : 23
at Ambient Temperate 40c and Humidity 60%

In this phase of your testing, the high, high-side pressure indicates a condensing problem, which is probably causing the warm-ish 23°C (73°F) vent temperature. In other words, not enough air is flowing through the condenser. Were the fans running at a high speed and making a roaring sound while you were testing the pressures?

After Driving for 15 minutes with the Fan on High Speed at 2200 rpm the vent temperature dropped to 17c and when parked at 800rpm the vent temperature dropped to 15c, on low fan speed the vent temperature dropped to 8c.

While driving, the vent temperature was 17°C (63°F), so it's going in the right direction but still too warm in my opinion. The idle vent temperatures should be higher than the driving vent temperatures, so something seems out of whack. The 8°C (46°F) vent temperature is much better and more like what it should be while driving at your ambient temperature of 40°C (104°F).

A few issues come to mind that might be causing the higher than expected vent temperatures while driving:
—Poor airflow through the condenser caused by insects, debris, weak fans, missing insulation, etc., and also poor condenser heat transfer caused by corrosion between the fins and tubes.
—Air and moisture in the system.
—Defective TXV.

Was the TXV you installed an OEM part or aftermarket? The reason I ask is because some brand-new aftermarket TXV's have been known to malfunction right after installation.

[tbirdtbird]

"The idle vent temperatures should be higher than the driving vent temperatures, so something seems out of whack. The 8°C (46°F) vent temperature is much better and more like what it should be while driving at your ambient temperature of 40°C (104°F)."

Fan was on low

[JohnHere]

Fan was on low

Excuse the lack of clarity. My intended point was that the 8°C (46°F) vent temperature is more like it should have been while driving, not necessarily what it was at idle with the blower on low.

[tbirdtbird]

Sorry I questioned you

[sherqa]

Dear JohnHere,

Thanks for your time and detailed reply.

Yes the fans running at a high speed was making a roaring sound.

The OEM TXV was not available, I found aftermarket TXV and replaced the old one.

When I removed the Old TXV, the Adjustment Screw was lose not fully tight, Last year while replacing the Evaporator the mechanic removed the TXV screw and did some cleaning to the old TXV, I guess he didn't properly tighten the TXV adjustment screw because from that day the cooling was very poor.

[JohnHere]

Yes the fans running at a high speed was making a roaring sound.

That's a good sign.

The OEM TXV was not available, I found aftermarket TXV and replaced the old one.

Aftermarket TXV's have been known to malfunction from time to time right after installation. That's why I favor the OEM part whenever available. Hopefully, yours is okay.

When I removed the Old TXV, the Adjustment Screw was lose not fully tight, Last year while replacing the Evaporator the mechanic removed the TXV screw and did some cleaning to the old TXV, I guess he didn't properly tighten the TXV adjustment screw because from that day the cooling was very poor.

If the adjustment screw was loose, I'm not surprised that the system didn't cool well. The screw is called a "superheat adjustment screw" that regulates, in part, how much refrigerant the TXV allows to flow into the evaporator. It requires a specific adjustment for the TXV to work properly and should be fairly snug against its spring so that it doesn't move in service. Sounds like the mechanic didn't know about that important detail and unknowingly threw-off the factory setting.

Do you think that the system is working well enough now given your very hot daytime temperatures, or do you think it needs further diagnosing? If so, I'd look closely at the condenser next because the high-side pressure seemed rather high, which will compromise cooling as well. Did you find anything on the front of it that might be partially blocking airflow, like dead insects, plastic bags, leaves, or the like?

[sherqa]

I didn't find any dead insects or plastic bags on the front as I am flushing the condenser time to time with pressurized water.

The system is working much better now, my only concern is the high discharge pressure, I guess some blockage inside the condenser or the dryer filter.

I am planning to use it this summer as it is and open the condenser before the next summer and check if it requires replacement.

[tbirdtbird]

" I am flushing the condenser time to time with pressurized water."

Pressurized water, as in a garden hose, or as in a electric powered so-called pressure washer...

[JohnHere]

" I am flushing the condenser time to time with pressurized water."
Pressurized water, as in a garden hose, or as in a electric powered so-called pressure washer...

Good question, tbirdtbird. OP should remember that the condenser core is delicate, and the fins can be easily damaged by water, even at garden-hose pressure, and also by the stiff bristles of a scrub brush. The idea is to spray on your favorite detergent, wash gingerly, and rinse gently. A pressure washer should never be used.

The system is working much better now, my only concern is the high discharge pressure, I guess some blockage inside the condenser or the dryer filter.
I am planning to use it this summer as it is and open the condenser before the next summer and check if it requires replacement.

It will be hard to determine whether the condenser is blocked or partially blocked by examining it. Blockage typically occurs when a compressor begins to disintegrate internally and sends debris downstream that lodges in the condenser. But that hasn't happened to your compressor. If you have any doubt, I would go ahead and just replace the condenser, along with the R/D.

[sherqa]

" I am flushing the condenser time to time with pressurized water."

Pressurized water, as in a garden hose, or as in a electric powered so-called pressure washer...

Dear tbirdtbird, good question.

It is not an electric pressure washer, we have a water pump fixed to the water line for water supply, the water pressure is soft on the condenser just enough to remove the dust particles.