I swear, I’ve never had a car with this finicky of a heater, and I’ve owned several piles of junk. Specifically, my heater runs cold when the engine is not revving (like at stoplights), A quick search reveals this is a common and well-known issue relating to the design of the engine cooling system. It may just need more coolant (although it doesn’t look low) but I am surprised at this being so prevalent. Like I’ve said, I don’t recall ever owning a car where this was an issue. I’m no engineer, but heating a car does not seem like a really difficult proposition. Seems odd to me, especially for a flagship luxury car, but I guess there is a reason they designed things this way.

Also, is there really no way to turn the A/C on and off without some serious menu diving? Seems like something they would want to make more accessible.

 

If it runs cold at stop lights that’s not normal if you have extended idle day 20 mins it might run cold. Check the coolant level a tiny bit low even will affect how it behaves

 

I have no issue with heating what so ever.

In order to turn off AC, press on "Climate" and then the "A/C" button (2007-12).

 

Thanks, I probably wasn’t clear above — I understand that’s not how the heat is *supposed* to work. And I will add more coolant. I am just surprised a car of this sort is this picky and even small deficits in coolant will render the heater barely usable.

 

Can I do some divination here? You're losing coolant in the valley (all LS'es do that at some point). Another telltale sign is hearing fluid moving behind dash (pass side) when starting car cold (indicates critically low coolant level).

 

That seems reasonable. But in the 13-17 (which is what I have) it appears like the only way to do it is Menu —> Climate —-> A/C —-> on/off. All using the Lexus mouse (no touchscreen). Which is cumbersome, to say the least. I wish there was just an A/C on/off button on the dash like in my old Camry.

 

Air in the coolant system can cause this symptom. There's a plastic Torx type nut on top of a fitting just aft of the radiator top side to let out air.

 

You do need to establish if you are loosing coolant or not. If you are, no amount of coolant can fix the issue. As it was stated, valley plate leak is very common with such engine. I would inspect the radiator as well especially at top of the radiator and the water pump.

 

It's kinda hard to pinpoint the valley leak, esp on rwd cars. We usually lift the car then use inspection scope and feed it towards the top of engine-tranny joining area (it's right behind the valley area), then look for spots left by coolant. On AWD it's a bit easier as we can usually feed the inspection camera to the same area but from under the hood.

Attaching pics to demonstrate the scope of the problem - that's from my previous 2010 AWD 460L that only had 95000miles on it. Nothing were visible before taking off intake, just some dried coolant spots on the tranny bell....

 

My 2012 does not that problem. For what it's worth, my car has this:

COLD WEATHER PKG
includes: windshield wiper deicer, enhanced interior heater, high-capacity battery

And I always wondered what that means. Is there an auxillary electric heater? I've searched here and don't remember anyone having an exact answer.

 

Cold weather pkg consists of: windshield with heated wiper area + PTC-heater (Peltier heater unit, that helps heating interior up quickly) + bigger battery (96 i think)

 

I have cold weather package. I had a serious leak at 150k miles, though I am not sure how long it is being there.

 

First, check your coolant level.

My 2010 LWB just exhibited the same symptoms, I added some coolant and it is back to normal.

Even a little bit of low coolant can cause this problem.

You can figure out later if have a leak or not.

 

AC needs to stay on all the time BTW, but no what you're experiencing isnt normal

 

This, make sure that you have no air in the system as well. It can be somewhat difficult to bleed vs a more normal/older car