I'm trouble shooting some AC issues and trying to understand how the AC Amplifier will react when error B1421 and B1424 occur.

A search said to ignore these error codes when indoors, but i have a question...

Will this error impact fan speed (Blowing through the vents) or r134a flow through the evaporator?

1 - If feels like there should be more air flow when on high
2 - The evaporator gets down to low 40's temp when air flow is on low, but when on high (Which still isn't blowing as hard as my son's 07 Accord), the evaporator is unable to maintain the low temps. Feels like something is restricting the flow of r134a.

Any thoughts?

ST

 

The AC amplifier powers the climate control/ac system. Not sure if replacing it solves your problem. Probably should have the dealer diagnose and find out what they suggest. It could also be related to a sensor.

 

Sit in the sun, reset the DTCs and see if they reappear.
If the 2nd one does, it could relate to a faulty solar sensor, or connection.

I don't know how the Lexus AC works but my old commodore would blow the air on high if it detected sun in automatic mode. If your system won't blow air hard on auto but will on manual then it's likely a sensor issue. If it won't blow hard on manual then you have a separate issue.

 

Thanks for the help! You were correct, the errors went away, when checked in sunlight.

The restricted r134a flow was caused by a faulty expansion valve.

Does anyone know how many RPMs the the blower should turn when on manual high?

• The blower speed varies correctly, based on the setting, low-med-high, but it feels like the range is dialed back proportionally.
• High, doesn't feel like it blows as much as my Subaru nor my son's 07 accord.
• I have a charcoal filter in it. Will that type of filter restrict airflow?

Maybe the fan speed is just in my head.

Thoughts?

 

If you feel the airflow is weak across the board, simply remove the AC filter, it takes 2 minutes. Check for debris around the filter and under the bonnet where the air intake likely is.