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Discussion Starter #1
What's the procedure to run an AC module self diagnosis? For other Lexus models i see you have to press at the same time Auto + Recirculate. However, the IS doesn't have an auto button (just a position on the dial).

Problem is i'm getting no heat (or extremely little heat) in the winter - and the AC is blowing lukewarm air in the summer.

The interior temp sensor is working fine - tested it with a heat source, the temperature servo motor starts moving (as it should - i think...).

So to the temperature motor / stepper / servo or whatever it's called is working fine (i even tried removing it and moving the lever attached to it by hand - still no heat, no matter the position).

The ac mode position servo is also working, the recirculation servo is working and so is the fan.

The heater pipes - one of them is not insulated - could not check properly if it was hot or not, but the other pipe (not insulated) was hot.

Trying to diagnose this thing before i start tearing the dashboard apart... any help would be appreciated.
 

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What's the procedure to run an AC module self diagnosis? For other Lexus models i see you have to press at the same time Auto + Recirculate. However, the IS doesn't have an auto button (just a position on the dial).

Problem is i'm getting no heat (or extremely little heat) in the winter - and the AC is blowing lukewarm air in the summer.

The interior temp sensor is working fine - tested it with a heat source, the temperature servo motor starts moving (as it should - i think...).

So to the temperature motor / stepper / servo or whatever it's called is working fine (i even tried removing it and moving the lever attached to it by hand - still no heat, no matter the position).

The ac mode position servo is also working, the recirculation servo is working and so is the fan.

The heater pipes - one of them is not insulated - could not check properly if it was hot or not, but the other pipe (not insulated) was hot.

Trying to diagnose this thing before i start tearing the dashboard apart... any help would be appreciated.
You may have moved the mode lever. The air mode servo it near the firewall . Behind the mode servo. Both can move by hand care fully. The trick is the motor inside must move it.
 

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Discussion Starter #3
levers were in place when i first opened up the glove compartment, took a close look, both were moving and moving the arms they were attached to...
 

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Discussion Starter #5
turns out the levers and stepper motors are working fine, but the heater radiator is not - i have checked the 2 pipes from under the dashboard, one is hot, one is not (i guess the return pipe is the cold one).

coolant level is fine...

clogged radiator? can i use some radiator additive flush to clean it? or do i have to flush is properly (remove pipes and then do a straight flush) ?
 

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turns out the levers and stepper motors are working fine, but the heater radiator is not - i have checked the 2 pipes from under the dashboard, one is hot, one is not (i guess the return pipe is the cold one).

coolant level is fine...

clogged radiator? can i use some radiator additive flush to clean it? or do i have to flush is properly (remove pipes and then do a straight flush) ?
You can try to flush it. But I would replace the heater core.
 

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Discussion Starter #7
a new heater core is expensive and replacing it is a pain in the ass - removing the whole dashboard and stuff...
 

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I've been using the heater for about a week, but it's now starting to do the same thing. I can run the heater for 30 minutes or so and then it'll shut off for a couple hours.
 
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