A/C not cold in idle

[batich]

Please advise!

1993 Lexus ES300. 

In the idle on low RPM  AC blows warm air. On a higher RPM or while moving - the AC becomes cold.

Also the car overheats after 45 minutes with AC on.  Without AC it does not overheat. I am not sure if these two events are related.

Please assist!

 

[1990LS400]

The first thing I would check are the drive belts.  Maybe the belt(s) driving the AC compressor and water pump are slipping.

[Mike B.]

Your condenser fan is not working. Either the electric fan has failed or the relay may not be working. It works as you drive because you get airflow over the condensor, when you are not moving no airflow and this causes head pressure to rise until it shuts off the compressor. I'd venture a guess that both are related, I can't remember anymore but based on your symptoms I'm guessing it has a single fan so it pulls double duty. It isn't working so airflow over the condenser and radiator is insufficient.

[batich]

2 minutes ago, Mike B. said:

Your condenser fan is not working. Either the electric fan has failed or the relay may not be working. It works as you drive because you get airflow over the condensor, when you are not moving no airflow and this causes head pressure to rise until it shuts off the compressor. I'd venture a guess that both are related, I can't remember anymore but based on your symptoms I'm guessing it has a single fan so it pulls double duty. It isn't working so airflow over the condenser and radiator is insufficient.

Mike! It was my first guess too. Until I tried to rev up the engine up to 2500 RPM  IN NEUTRAL. In place. Not in driving. And the air flow became COLD. At 1000 RPM it is warm.

 

[batich]

30 minutes ago, 1990LS400 said:

The first thing I would check are the drive belts.  Maybe the belt(s) driving the AC compressor and water pump are slipping.

I was thinking of this too. How to check the belts for slipping?

[1990LS400]

5 minutes ago, batich said:

I was thinking of this too. How to check the belts for slipping?

The belts should not flex much when you push a finger against them - WHILE THE ENGINE IS OFF!

Sorry, but forgot I was in an ES forum which has a transverse V6.  The electric fan(s) behind the radiator are super important - verify it or they are working.  I'm more familiar with V8 Lexus vehicles in which the electrical fans are supplemental and run when it is very hot and then mainly when the vehicle is not moving.

[Mike B.]

10 hours ago, batich said:

 

Difficult to diagnose a car over the internet but based on what you've posted I would be looking at a possible low charge, partially blocked condenser or a failing compressor. Possible the expansion valve is clogged as well. You need to hook up gauges and read high/low side pressure. That will give you a starting point.