huesero

I have a 1997 300 ES with 125K mi. This is a problem thats been going on for a while now and getting progressively worse. Now that summer is coming, Im finally going have to get it fixed. I thought I would pick the brains of the expert enthusiasts before I lay down some coin.

When the car is idling or relatively cold, and running level, the A/C works with the green light on the button.
When the car heats-up, or runs on a grade, the light on the button goes out, and so does the A/C.
If you push the button twice, the green light goes on, and so does the A/C, for a while, and it cycles all over again.
You can hear and feel the compressor cycling on and off with this maneuver.
When it first started happening, the time lasted longer. Now it seems that the cold air is only on for a few minutes before it happens.

I searched the threads and posts and these are some of the responses I've seen:
1) Replace A/C filter
2) Refrigerant deficiency
3) Magnetic clutch relay dysfunction
4) Compressor malfunction

I opened my A/C filter housing only to discover there was no filter in there.
While putting one in will help my lungs, somehow, I doubt putting one in will solve this problem.

Charging the system seems easy enough, but its not an issue of being cold enough, as it seems to be cool when it actually works.

What and where is the magnetic clutch relay?
Is it costly? Can you replace it yourself?
Is there anyway to differentiate this switching mechanism from the actual compressor?

Replacing a compressor sounds the most expensive. What is a reasonable cost to install? I imagine this would also require re-charging the system.

Finally, I seem to remember seeing someone being able to display diagnostic codes on their radio by pushing a combination of buttons during start-up on an LS model. Is this possible with my ES?

Any tips are much appreciated.

RTIS250

iTrader: (9)

You are correct, there are a few things i would definately look at. Your A/C could be under or over charged, causing the A/C to turn off. It's definately not your cabin air filter. Im guessing that most likely you have a bad A/C clutch or a compressor that is beginning to seize. You can look at the A/C sight glass and see if there are bubbles in the line, which would indicate a low charge. But it sounds to me like the A/C does work well when its working, so that leads me back to the clutch slipping or compressor seizing.. You should be able to let your car idle, with the A/C on, pop your hood, walk around to the passenger side front of the engine, thats where the a/c compressor is located.. with a flashlight, you should be able to see and hear the clutch slipping when you reach over and rev the engine.

mitsuguy

iTrader: (2)

I would look into having the system pressures checked... if the high side pressures are getting too high, the system will cut itself off trying to save itself... you need to first make sure that the cooling system is in top shape, and the cooling fans are both working...

your problem very well could be something as simple as a cooling fan not working causing a/c head pressure to get too high, causing the system to shut itself off in an effort to save itself...

so, before you start in on a/c stuff, make sure everything else is working properly - radiator is free from defects and car is maintaining proper temperature, both cooling fans are working, so on and so forth... once its established that the engine cooling system is working properly, then its time to get into the air conditioning system...

here, we want to look at high and low side pressures... somewhere around 35 psi on the low side, and 250 psi on the high side... as much as 300 is acceptable, depending on weather, but if high side gets above that, then something is wrong... on the low side, if you see much below 25 psi, then good chance the system is low...

here's where it gets tricky though - if the fans are working and the high side is very high, then more troubleshooting... get this stuff checked out first and report back...

edit: being as your car is R134a refrigerant, looking at the sight glass won't tell you anything usable from a diagnostic standpoint - most manufacturers in fact did away with the sight glass on 134 systems because it's just not a reliable indicator of charge status like it was with R12 systems...

98LexLs

I would check your ac drive belt, not enough tension would cause ac clutch slippage also try spraying the belt with water and see if the light starts to flash.

scargo

Thanks for the great suggestions here. This must be a tricky problem. Our RX300 suddenly stopped cooling (just blows warm air), and our Manhattan Lexus servicemen have not been able to fix it. They have tried 3 times, including replacing the compressor. We've been charged a whole lot of money, but the situation is still exactly the same.
Needless to say, we're angry and disappointed.

mitsuguy

iTrader: (2)

I hate when A/C guys guess at the problem by just replacing the compressor... there are so many other parts that can fail, but typically don't, so they get overlooked all the time...