2011 LS460, 26,000 miles. About a year ago, the dealer changed the air filter for the a/c. (I believe it was the filter behind the glove box.) Since then, the a/c has done, among other things, at least once: Cold air through upper vent, though temp was set for 72 and ambient tempt was 61; outside temp read 73 for hours, though the actual temp was colder; noisy fan at bottom vents, but very little air flow; cold air through top vent and warm air from bottom vents, simultaneously; cold air through top vent when starting, though setting was for 72, and outside temp was in the 60's.
I took it to my Lexus dealer, who says they "couldn't duplicate" anything abnormal with the a/c. I'd read, perhaps in Club Lexus, that a bad "a/c amp" could cause problems such as these. If memory serves, the amp is located in the area where the filter was replaced. The dealer won't replace the amp, because they "can't duplicate" a/c problems.

What do you think?

 

Is it because they don't want to warranty the service? Hold the BIG AUTO button and the recirculate button while starting the car and keep holding them until ALL the AC lights start to flash before letting them go. The display will give you 2 digit codes if anything is wrong with the servos. 00 means everything is working properly. You can ignore 21 24 and 28 because they are solar sensor codes and if you run the test when it's dark it sets them off.

 

It's not a matter of warranty, the car is way past that, it's that the odd things began happening right after they changed the a/c air filter. It's a lousy dealership, but the only one near me.

I'm not a DIY, and don't understand the parts of your message about codes. Do you think it could be the "amp"? Is the dealer right that if they can't duplicate an event they can't go further?

Thank you

 

You do seem to have a lot of different issues. I would suspect the ac amplifier. But first I would check to make sure the door that controls outside vs inside air is moving as it should. My AC was exhibiting similar issues randomly blowing hot or cold on different sides or not at all. The ac amp took me about 30 minutes to replace. It is behind the glove box near the stereo. The stereo does not need to be removed. I picked a used one up on ebay with a warranty for around $75.

If I were in your shoes I'd probably buy a used ac amp and pay someone to install it. I'd guess a small shop or mobile mechanic could swap it out for $100.

 

Thank you for sharing your expertise. I've not yet finished with the dealer. I picked up the car today, after they'd said they couldn't duplicate the events, and therefore did nothing. Outside temp was 64 degrees. The a/c was set for 73 degrees AUTO. COLD air gushed from the dash vents at fan HI. I gave it a few minutes to see if it would adjust, it didn't. I had to manually set desired temp to 76 degrees before cold air stopped.

I'll be speaking to the "Master Certified Service Consultant" (remember when they were "service writers"?) next week.

 

Update. I discovered that when the outside air temp was 63 degrees, inside the car temp 66 degrees, a/c set on AUTO 75 degrees, DUAL, cold air came from the two driver side upper vents, the passenger side vents blew warm air. Does this give anyone a clue to the problem?
Dealer Assistant Service Manager insists (via phone) that as they were not able to duplicate any of the many a/c problems I reported, they can do nothing more. They'll change the a/c amp, if I wish, at my expense.
Of course, COVID-19 is what's really important, but I intend to follow up when/if things return to a semblance of normal.

 

So you have DUAL set, are the temperature settings on both the driver and passenger side set to the same temp?

 

Yes, they are.

 

If you turn dual off, does it still blow hot air out one side and cold out the other?

 

I don't know. When I next take the car for its weekly 20-minute freeway run (I don't use it daily while on lockdown) I'll check and report. This is just one of the problems with the a/c since they changed the air filter (details above.)

 

I checked: Both side temp settings were 75 degrees. The air from the driver's side vents was very cold. I hope to take the car for a run soon, and will see what the a/c is doing.

 

It gets more weird. A couple of weeks ago, it was cold air from the driver's side upper vents, warm air from passenger side upper vents.
Four days ago, when I next drove, it was warm air from the driver's side upper vents. no air from the passenger side vents. The icon showed air to both the upper and lower vents, but nothingwas coming from the lower vents
Switching DUO on and off had no effect.
Both times, a/c was set for 75 degrees, outdoor temps 55>63, interior temps about the same.
It was raining, and the windshield wipers didn't turn on automatically, as they always have. I had to turn them on manually.

The dealer service assistant chief, who previously had said they couldn't duplicate a/c problems and that was that, now says she will give the latest info to the shop foreman, and I should bring the car in when social distancing permits.

.

 

again...I had the same issues changing my ac amplifier fixed them. All of these settings get fed through the ac amp. You will find it will randomly do many different combinations the worse it gets.

cold air from the driver's side upper vents, warm air from passenger side upper vents.
Four days ago, when I next drove, it was warm air from the driver's side upper vents. no air from the passenger side vents. The icon showed air to both the upper and lower vents, but nothingwas coming from the lower vents

https://www.ebay.com/itm/07-12-Lexus...UAAOSwROleTsi~

$35 free shipping and a 60 day return. Then pay a shop for 30 minutes of labor to put in it.

Or if it makes you feel better your dealer should be happy put a new one in for $1500.

 

Thank you. Is there anything about a bad amp that would keep the auto windshield wiper function from working? The problems began immediately after the cabin air filter (behind the glove box, I believe) was changed. Do you think the amp could have been damaged by the mechanic changing filter, is it located in that area? Was the eBay amp you purchased used? A 60-day warranty isn't long, and if it fails, I'd have to pay the shop to uninstall it, then to reinstall the replacement.

 

No, the two issues are not related