Occasional A/c Issue

[V-10]

Hi All

First of all, thanks for the time and moolah saving tips I've gleaned from many of you.

I've had an intermittent air conditioning problem. When driving cross country for 100 miles or more the center a/c vents don't seem to put out much air volume. They will work fine most of the time or around town but after a few hours on the road it doesn't blow like it should. One time I even had a electrical smelling vapor coming out of the vents. Only happened once?

I've replaced the interior cabin filter but I can't figure this one out.

Suggestions would be appreciated.

Best

Steve

[flanker271]

I have the same problem on my 92 LS. The two center vents, occationally, hardly have any air coming out of it. When I set fan speed to mid, it seems like the setting was on low. When I set the fan speed on high, I can hear very loud whirling fan noise, but there is still very small volume of air coming out of the vents.

Haven't got the faintest idea why. Also, my side vents seems to blow 10 degrees hotter than my two center vents.

Could the problems be bad a/c control unit or does it have something to do with a valve somewhere?

[wwest]

I have had this happen to two separate 92 LS400, both times while traveling over mountain passes during hot weather. The first time, June 92, was over the Continental divide westbound out of Helena MT. Since the A/C was doing no good, virtually no airflow, I turned it off. When I turned it back on west o fthe pass it worked fine and has ever since.

Last year I drove a 92 from Tucson to Seattle and just north of Mt Shasta had the same thing happen again. Suspected the same problem so I turned it off for a few miles and then it worked fine when I turned it back on.

On many occassions, for both cars, I have noticed that the refrigerant return line to the compressor will ice over with rime ice up to at least 3/8" thick. So I suspect that for some reason the evaporator is icing up and blocking all or most of the incoming airflow.

Lexus, on the 92, does not directly prevent the evaporator surface temperature from reaching freezing level. They only regulate the pressure gradient downstream of the evaporator and my guess is that atmospheric pressures in high mountain areas somehow "fool" the regulating device.

Side vents hotter....

Lexus lays claim to the use of a bi-level climate control system wherein the airflow in the lower parts of the cabin is typically 20F warmer than the airflow into the upper parts of the cabin. For whatever reason the side vents are considered to distribute airflow to the lower portion and therefore is connected via the lower airflow outflow path.

That 20F difference is also why your windshield will be much more prone to fog over in the wintertime, with comfortably warm airflow coming from the footwell vents the airflow to keep the windshield warm will be as much as 20F colder. And be careful and attentive to the fact that the climate control system wil automatically switch to cooling mode on the coldest night in the dead of winter once the cabin temperature approaches and/or reaches your comfort setpoint level.

At that point the windshield will be recieving virtually no airflow at all and the impinging COLD outside airflow will soon chill it to the dewpoint of the interior atmosphere. You will soon see little wisps of condensation on the inside of the lower portion of the windshield and like most of us you will instinctively react by activating the defrost/defog/demist mode.

Then.....

ZAP!

Fogged over windshield!

Completely! No forward vision!

Don't EVER let the system switch to cooling mode on a COLD day.

The new RX330 has a C-best open that can be set to prevent the automatic switch to cooling mode for exactly the above stated reason. Maybe next year the entire Lexus line will have that feature and maybe even be shipped, at least to the northern regions, already set correctly.

[flanker271]

How do I make sure that it doesn't switch to cooling mode? By not pressing the "Auto" button?

Also, on cold days ~30-40 F, despite the fact that I set the temperature to 70F (A/C off), the vents will still blow warm air. I turned the temperature all the way down to 65F, and this has no affect on the air from the vents....still hot air coming in. Is this an auto feature or is it malfunctioning?

All these features really made me confused.

For whatever reason the side vents are considered to distribute airflow to the lower portion and therefore is connected via the lower airflow outflow path.

So it's normal for the side vents to blow warmer than center vents correct?

[flanker271]

One more thing to add: After driving for a while, the hot air will change into normal room temperature air flow automatically without me adjusting the temperature dial.

All these are features, not malfunctioning, right?

[bstrope]

Hi there!

I recently purchased a 93 LS400 with A/C that seemed to blow very weak even when on HI. The previous owner told me he noticed the same thing for the last year or two but didn't know what was causing it. I called the local Lexus dealer and they told me to check the "Pollen Filter".

Under the dash on the passenger side....you have to drop down the pannel just above the passengers feet. (it's a pain to get down but you'll see...)

When you get the panel clear, you should see two wing nuts.....take these off and you should be able to pull the filter down and out. My 93 had 190,000+ when I got it. The filter was badly clogged. I tried to clean it but it's rather fragile. The dealer wants $58.00 for a new one. I decided to put it back together without the filter. (...never had one in any of my other vehicles ...and I ain't dead yet! )

Darn thing blows like a wind tunnel, now! Gets the inside so cold, I don't put it above medium....even on 100 degree days. Hope this helps!

Regards,

Bryan

Post Falls, ID

[wwest]

In automatic mode if the interior is cold when you start it up and set the temperature control to 72 the airflow will be moderately high and almost uncomfortablely warm (actually uncomfortable if the outside temperature is COLD) until the interior rises to about 5 to 10 degrees within the 72F setpoint. Once it reaches the setpoint it will automatically switch to cooling mode and now the airflow to your face and upper body will be discomforting by the coolness and dryness of the airflow.

In the wintertime the best procedure is to first put the system in automatic and then place the airflow routing, outflow, to the footwell mode. all other functions will remain in automatic mode but the outflow will be locked.

[chuckb]

I have a 95es that had similar prob.

After you drove it for about an hour or more the air would start blowing warm. Also started to blow warm out of driver's side vent first.

If you drove under hour air blew ice cold.

I took it to my mechanic and he found no prob as it was an intermittent prob.

I finally got it to act up near his shop & went right there.

He checked and it showed a BAD EXPANSION VALVE. I made an appoitment to get fixed. When I brought it in for repair it was blowing ice cold in 90 degree weather.

But the fix worked!

[flanker271]

Thank you all for the input. I'll check both the pollen filter and the expansion valve tomorrow, and will let you all know what I find. Also, my two rear vents doesn't have any air coming out (yes I tried the knob to the right :) ). Which airflow outflow path is the two rear vents connected to?

Moreover, what exactly does the expansion valve do anyway?

[flanker271]

Just learned that 90-92 isn't equipped with a pollen filter. hmmmm........