'96 LS400 A/C restricted air flow? Freezing up?
 

Good day everyone!

I am the third owner of a very well maintained 1996 LS400, just short of 300,000KMS. I have owned it for about six years, never a problem - with ANYthing...

Just had the A/C charged and it is blowing colder than ever.

Yesterday my wife and I were traveling into town, about a 30 minute drive on about a 75F day and 20 minutes into the trip the air flow diminishes to nothing. I had the fan set on Speed 2 (of 5). I increased the fan (blower) speed to 5 (Max Setting) and the airflow did not increase. The small amount of air coming from the vents was still cool, but barely flowing from the vents.

I turned off the A/C and the air flow gradually increased to full flow and stayed cool for about ten minutes. I adjusted the fan speed back to Speed setting 2. When the air temperature began to warm I turned the A/C back on and all was well for about ten minutes then the air flow again began to become restricted somehow? I repeated the procedure by again switching off the A/C - air flow returned, etc....

Is my A/C system freezing up? Why does the airflow on a normal A/C setting on a moderate day become restricted yet remain cool, and why does airflow return to normal when I switch off the A/C? Cabin filter is brand new. I tried all vent settings and the symptoms remain.

Please help all!

Thank you!

you might try having your system evacuated and recharged with the proper "freon", they are not all alike, you should have a label (R134/?) under hood stating what is in it.. as an after thought, I would remove the new cabin filter first and try it without one for a few days (that would be free) and compare what happens.. if it is not freezing up then your air flow is restricted... good luck

Thanks for your suggestions.
- it was topped off with R134A refrigerant matching the factory
- tried running it without the cabin filter and the same symptoms occurs exactly as described in my thread

So what would cause air flow restriction in the situation as detailed? This seems very odd to me. I live five hours away from any Lexus dealership.

Hoping for more suggestions please all.

Please - any other suggestions or possibilities?

this is common knowledge for AC systems... not directed at your car, but you can follow the thought pattern :
It’s good to start with the basics but if the cabin air filter and the blower are not the cause of low airflow, then an actuator or HVAC door could be the problem. Sometimes an actuator which is a small electric motor or vacuum operated device for moving the doors within the case can fail. Without the actuators working properly the air isn’t directed the way it’s supposed to go causing low airflow or incorrect airflow. Other times the door itself can break causing similar problems. If the fresh air/recirculate door breaks, it can sometimes fall down over the blower fan almost restricting the airflow completely.
good luck..
edit: as an afterthought, I owned a repair shop for 30 years, BUT, I retired at 62, 80 now, that is 18 years since I was active.. so my thoughts may not be up to date with our LS's, just cut me a little slack..

You'd better check the pressure of low side and high side when the problem is happening?
I worry about the gas was not charged properly and precisely?

Also reading the DIAG code for the A/C will help but this needs a service manual to perform. I only have a thick Japanese manual and I can't show it to you.

It sounds like your evaporator is freezing up. I suspect that the condensate drain is plugged up not allowing condensation to drain. The drain hose is pictured here:

https://www.clublexus.com/forums/3064102-post5.html

I you run your A/C while parked, do you see water dripping under your car? If not, use compressed air to try and unplug it.

Thanks! I will give that a try!

That is a pic of the radiator coolant drain hose.

Yes it is, my mistake, sorry. I see that clearly now but didn't pay much attention when posting.

I believe there are two of them and they are back by firewall. You'll prolly need to put the car up on jack stands to get to them.

Check the freon charge
 

If the system provides good cabin airflow at the dash vents, you don't have a restricted air handler. It may be possible the blower fan is somehow bypassing the evaporator, and drawing air from somewhere else, but I haven't seen that happen before. Plugged evaporator drains do not cause icing; they cause wet carpets. You most likely have a low refrigerant charge, check the sight glass at the condenser (in front of the radiator). Search for the proper indicators and process in this forum.

It's not a problem, that drain hose is located somewhere around the passenger foot well/firewall area. Like you said it's easy to spot if you have the AC running while parked.

The key is probably in the first post: "Just had the A/C charged" etc. Before it was charged, was it blowing normally? Could be it is overcharged and if you raise the hood when it's blowing slowly you will likely find ice on or near the drier.

Keep us posted.

No the A/C was very weak prior to the charge.
Now the A/C is icy cold, at least for the first half hour.
Another thing I note since the change is that the compressor whines when the A/C is engaged, it didn't before the charge.
I charge the A/C myself with a kit. I do not know what pressure it charged to. I could take it to a local fellow to check the A/C line pressure.
What should the pressures be?
When should I check them? Running? Not engine running?
Thanks all!