What controls the A/C button on the dashboard?

If your tail lights are not working on your 2019 Toyota Sienna, but your headlights and flashers are, and multiple warning lights have also come on, it could indicate a problem with the vehicle's electrical system. Here are a few things you can try to troubleshoot the issue:

1. Check the wiring and connections. Make sure that all the wiring and connections for the tail lights are clean, tight and free from damage.
2. Check the tail light relay. The relay switches the power to the tail lights, if it's faulty, it can cause the tail lights to not work.
3. Check the body control module (BCM). The BCM is responsible for controlling the lights, if it's faulty, it can cause the tail lights to not work and also trigger warning lights on the dashboard.
4. Check the vehicle's software. Sometimes, the problem can be caused by a software issue. It's recommended to take the vehicle to the dealership and have them check the software.
5. If the above steps don't solve the problem, it could indicate a more serious issue with the vehicle's electrical system. It's recommended to contact the Toyota dealership or a professional technician for further assistance.

It's important to follow the manufacturer's instructions and guidelines when performing any maintenance or repairs on the vehicle, to ensure the safety and proper functioning of the car.
It's also important to check the vehicle's warranty status and the manufacturer's instructions to ensure that the repair or replacement will not void the warranty.
Keep in mind that troubleshooting and repairing electrical systems can be dangerous if you are not familiar with the proper procedures.

The compressor has a clutch, the clutch engages to a rotating pulley by the use of a clutch. The clutch is an electric solenoid, or plunger.
This clutch, or solenoid clutch gets 12 volts from the controls. From a thermostat, thru refrigerant pressure switch, thru coolant temperature switch, thru ambient temperature switch, fuses and control switch.
Where is the ac magnetic relay? i think it's the clutch you are refering to.

Probably needs recharge or high or low pressure switch is bad.

First of all check the freon pressure, if the pressure is low the compressor clutch will not turn on. The pressure should be between 30-40 PSI.

If the a/c is not working, it's most likely the clutch relay. Under the hood next to the battery, there is a fuse and relay box. One will be marked magnetic clutch or an abbreviation of that. If the part number is 90987-02022,it should be changed out to the updated relay with a part number of 90987-02028. It 's around $70 from Toyota or you could find an aftermarket one for about $17 at your local automotive parts store.

The Sienna has had problems with the relay that controls the clutch going bad. Under the hood, next to the battery, there is a fuse and relay box. One will be marked magnetic clutch or an abbreviation of that. If the part number is 90987-02022, it should be changed out to the updated relay with a part number of 90987-02028. It 's around $70 from Toyota or you could find an aftermarket one for about $17 at your local automotive parts store. On some models the a/c light will blink if this is the case but not on all. You could swap it with the fog or possibly the horn relay to see if this is the problem.

Its the white relay in the fuse box under the hood of the van its marked (ccm) for compressure clutch magnet.

What happens when you leave the relay out? Your fan control module may have a shott.

Hello, I am a tec. from Puerto Rico your problem does sound like the magnetic clutch. It is located directly on the compresor, over here we change them for around $150 including materials and work.

Replace your magnetic clutch relay.
TSB EL011-05 : A/C LIGHT FLASHING - MAGNETIC CLUTCH RELAY 6/3/2005 - 2001 – 2004 Toyota Camry, ECHO, & Celica. 2002 – 2004 4Runner, Corolla, & MR2 Spyder. 2003 – 2004 Matrix, Sienna, & Solara. This bulletin is to provide information regarding countermeasures to the A/C magnetic clutch relay for A/C light flashing (inoperative A/C) issues on some vehicles equipped with a magnetic clutch compressor.
Applicable Warranty*:
This repair is covered under the Toyota Comprehensive Warranty. This warranty is in effect for 36 months or 36,000 miles, Whichever occurs first, from the vehicle’s in-service date.
* Warranty application is limited to correction of a problem based upon a customer’s specific complaint