A/c Problems 91 Ls400 - Looked At All Other A/c Threads

[Pacerdonfl]

I have had a 91 LS400 for a little over a year, and starting to drive it more these days. Over the year, the A/C has "flashed-out" and stopped cooling very intermittently.

I'm sure it's not the compressor freezing up, or it would not begin again to run properly, as it does. There is no (obvious) rhyme/reason when it cuts out and begins blinking, but it does that maybe once a week or two. Later or next day, works and cools perfectly. I replaced the clutch relay and still goes out now and then. It was converted to 134 a couple of years ago by previous owner (father). The electric fan on the drivers's side runs very slowly????

Any ideas would be greatly appreciated....

Thank you,

/Don

[landar]

Hi Donald and welcome to LOC!

Although I cannot tell you precisely what is wrong with your car from 1000 miles away, I can give you some ideas.

Ok, so you sound like you know the basics...the compressor comes on when the clutch is engaged. And that clutch is controlled directly by the clutch relay (which you replaced).

Although you replaced the relay, the relay has to be 'told' to engage. Maybe it is not? And maybe it is not because the freon level is low. Maybe. There is a pressure switch in the system that tells the controller that the system is ok. Maybe the pressure switch is bad or freon level is low?

And then you have the clutch itself. Maybe it is being commanded to pull in but occasionally does not?

You might consider hooking up a 'trouble light' to the compressor clutch coil such that when the compressor is being fed 12v, the light is 'on'. You could rig it into the cabin so that you can quickly glance over at it when the cooling cuts out. If it is off and you are getting hot, then at least you know something is commanding the clutch to cut out. Intermittent issues like this require a good deal of patience and testing but you can nail it down with some logical, methodical testing.

There are many other things like expansion valve, dryer, damper doors and evaporator core but lets go for the easy stuff first.

Let us know what you find.

[Pacerdonfl]

Thank you very much for your time and suggestions, Randall. I'll try the trouble light thing. I will also check the operating pressures on each side of the compressor....

Is there a source for diagrams/pictures to show where "sensing" items are, i.e. - the compressor pressure switch.

Also, I've also been reading that maybe there is a temperature sensor that could be faulty and telling the compressor to dis-engage?

Also, what do you make of the driver-side electric fan spinning very slowly???

Thank much!

/Don

[Exhaustgases]

I think this is an easy one, well not so to fix, just to figure out. I also have a converted to 134 one the compressor was seized when I got the car. The reason it happens is because the oil for 12 is not compatible with 134 so it ruins the compressor. I guess the right way to convert would be to completely clean the oil from the system and compressor. The compressor is likely freezing up slowly from lack of lubrication.

[landar]

Don, I should have mentioned that I would be concerned about the fan too. It really should be spinning fast with authority such that you would not want to get your digits anywhere close. But it sounds like maybe it is pretty anemic? If so, then check into the motor. Maybe it is close to seizing up or bad motor or relay contacts? In any case, that could cause the temperature of your cooling system to rise and maybe start to shut things down. Makes sense that when you get moving again, all is well with airflow. So, definitely dig into why that fan is running so slowly.

I think the pressure sensor may be mounted on the dryer but not 100% sure. Do not know about the temp sensor. Will try to check my documents to see if there are any clues.

[landar]

Been reading bits and pieces of the service manual...seems that the low fan speed may be 'normal'. The fans go high speed only when the engine temp gets above 181F. Now, it could be that your water temp sensor is bad (reading too low). Is your gas mileage ok... or poor lately?

[VBdenny]

The 1990 LS400 I had did the same thing. Light flashed, AC no longer cold, compressor stopped. Had it converted to 134 at a dealer and it ran for another 5 or 6 months then gone again. Had a friend who works at Toyota have his boys check it out and it turned out the compressor had destructed and send metal throughout the system. That's the bad news, now the worse news. In order to replace the system, the dashboard must be removed to access the internal components. Finally, the even worse news (if you can imagine) was the cost to replace was right around $2500 at 3 different places.

I sold the car for $2500 to my friend's son who was driving a ragged out bikini top jeep. He thinks the LS is cool

I of course, still miss the car. Best car I've ever owned..

[Exhaustgases]

The reason the compressor first stopped was low refrigerant pressure, when it drops a pressure switch says NO clutch engage to the compressor clutch. The mistake was the conversion and the wrong oil in the system. Yeah not an easy fix.