Hi
Im new here, and new to Lexus having just bought my first ever Lexus after 100+ BMW's over the years. I'm loving the LS600hl but there is an issue or two I am trying to solve.

The one I want to tackle here is the fact that the passenger side of my car (RHD) will only blow out cold air no matter what I do to the controls.

I have been lurking on this forum doing research and heard low air con gas can cause this but my garage confirmed I had a full compliment of gas in there.

I then read up about the blend door and went for a look. When I got there someone has clearly been there before because the 'lid' to the filter moves very freely but doesnt lift up when pressing the air recirculation button, so I assume it's either been broken before or it's out of line?

Surely though if I move the lid to the filter up by hand and use the recirculation feature I should be getting heat to all air vents no, because I'm not, I;m still suffering from cold passenger vents.

Here;s a pic or two of what I found when I looked.

Any help in assessing what I should do to fix the problem is gratefully received because my Mrs is refusing to sit in the car until it's fixed ha ha!




https://imgur.com/a/EGJ66hZ

 

i do not think blend door working or not working will effect the heat only comng from THOSE vents. i assume you have 4 zone control? so if you disable 4 zone control by disengaging the button in the middle of the up and down temp button closest to you ... what happens all the vents, yours the ones in the back blow hot air except that front passenger one?

Also check your coolant level when the car is cold, it has to be at full.

 

Hi - thanks for the reply.

I have 4 zone control yes. What I think happens (I will go out and check again now though) is that regardless of all settings I cannot get heat out of the passenger side of the car. All vents whether face, floor or the little rear ones in the door pillar blow cold air. I've tried turning the 4 zone off, tried it with the recirculation both on and off and tried a combination of vent settings (floor, face, mixture) and I get cold air only on one side of the car (both front and back).

I had been reading that the blend door could cause this phenomenon but maybe not?

I'll go check the coolant level now because I know the PO did at some point change the radiator....

 

OK, sit rep.

The engine coolant is on max and is a nice pink colour so I know it's full of decent coolant not just water.

I've just tried turning the 4 zone off and trying different settings and nothing is providing warm air to the passenger side of the car (right hand drive).

I had heard of this being fairly common, but in most cases the air con gas level was low.

What exactly does this blend door do then - does it only regulate the recirculation function??

 

when the recirculate is on the blend door is down. when outside air is allowed in, it is pushed through the filters behind the blend door.

That doesnt affect heat.

So on your side and behind you, you get heat?

 

Whether The filter door is open or closed you should still get heat. It's not actually a blend for heat. Hold the recirculate button and the big Auto button when you start the car and then wait until the AC diagnostic starts. All the light will blink and if any actuators are bad the temp screen will output a 2 digit code. Post them here if you get any.

 

thank you you very much for that tip!!!

ive posted a video of what happened.

at first the display said 88.8, then scrolled through 0-9 whilst displaying different areas of the vent system, and then spat out the codes 21, 24, 28 and 76. I think it might also have said 74...?

 

 

I had a similar issue, I resolved it by unplugging in the AC amplifier , pulling a tiny bit more slack in the wiring harness reconnecting it, then running the AC servo calibration in techstream (not even sure if the techstream step is needed). Did it a few months ago and no problems.

my issue was caused by the ac amplifier connectors being installed tightly. pulled hard and the pins weren't making a reliable ground connection (verified with a continuity test).

You might try it. It's free to try (except if you don't have a techstream cable) and might solve your issues. Maybe not, but worth a shot.

 

whilst it sounds like a long shot I’m up for giving it a go!!
is the amplifier easy to get at? Any pics or idea where it’s located please?

 

Don't worry about 21,24 and 28 those are solar sensor codes that turn on if you run the test while it's dark out. You can Google 75 and 76 or wait until I can check my manual in about an hour.

 

One question- when you start the car does it always say AC Off on the screen (after a few seconds),and revert to 75°F?
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I couldn't find any entries in the manual I have for 75 or 76, or their respective B1475/B1476 ac codes, Maybe Sha4000 can find them.

Super easy to get to. I don't have a diagram, but it's right underneath the glovebox. You can Google what the AC amplifier looks like to see what you're looking for. There's a cover you have to pop off and then it's right in front of your face. I couldn't find a good diagram for the location. It's a huge connector. Unplug it, see if you can get a little slack on the harness, inspect that all the wires are straight and their pins aren't pulling out, then reinstall the connector.

When i had my issue, I mostly got b1497 (code 97) but it would throw random codes on occasion. I would have issues where the inside/outside air door wouldn't close, and I'd only get hot air on the driver side and AC on the passenger side.

I just probed around with my multimeter and found I'd only get some ground continuity when I pushed on the wire harness. Without all the grounds working, you end up with noise in the circuit and the computers don't know what to do with it. It could be any of the 20 (or so) wires though. Im sure others have had this issue, and following a troubleshooting tree it tells you to replace the AC amplifier. I work on electronics for a living, so I wanted to repair the module if possible. I didn't even need to get that far. I'm sure most mechanics would do the same thing, replace the AC amp, and inadvertently repair the connector when they removed it and think that the AC amplifier was the issue. This kind of thing happens a lot in any repairs.
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If you have techstream,you'll be able to run the servo calibration, and that fixes AC things on occasion.

 

Thanks both, I very much appreciate your assistance in this. When I bought the Lexus everyone asked why I was departing from BMW’s and I proudly exclaimed that I wanted to get this LS to 300K+ and they were built for it. I now need to get the car to a point where it is highly likely to do that without the day to day annoyances that stop you from keeping hold of a car.

anyway, I’ll have a good look at the system tomorrow and test the car on start up as described. I did some Googling on codes 75 and 76 and came up blank but wasn’t sure if it was how I was searching.

fingers crossed tomorrow because the longer I own this car the more it’s starting to gel with me!

 

I see you have a right hand drive car so maybe that's where the code 75 and 76 come into play. On my US car you have to remove the glove box to get access to the AC amplifier. You can just disconnect the 3 plugs but it's still tight in there. There's no mention of those codes in my US manual either.

 

Ok I did a little digging and it seems codes 75 and 76 are specific to the hybrid system. I could only find it in a Prius AC diagnostic document.