Hello 
If you have a 419 code, and the compressor is seized, you need to remove the compressor, expansion valve (that is in the evaporator, access through the firewall), receiver/drier, and have the hoses/pipes flushed. When the compressor is seized, small metallic particles broken from it, can be lodged in the expansion valve, and the receiver/drier, or have potential to block the system if not flushed, before the components replacement. You can get someone else do the flush but they need to remove the above components, and replacing them with new ones will not be very labor intensive.
To answer your question, the expansion valve, as the name implies causes the liquid refrigerant to expand into gas in the evaporator, so that the expansion process cools the airflow through the evaporator cores. It controls the liquid to gas conversion, so the evaporator core never freezes.
The replacement compressor comes with the clutch and pulley and if you select the correct one, it will come with the correct size pulley. It is plug and play. I recommend genuine Denso brand, as the cheap ones tend to have quality issues.
If the compressor is seized, then there is really no need to check the voltage on the compressor. It is dead, and the coil fuse is opened to disengage the pulley from the clutch, to prevent belt damage.
If you have a 419 code, and the compressor is seized, you need to remove the compressor, expansion valve (that is in the evaporator, access through the firewall), receiver/drier, and have the hoses/pipes flushed. When the compressor is seized, small metallic particles broken from it, can be lodged in the expansion valve, and the receiver/drier, or have potential to block the system if not flushed, before the components replacement. You can get someone else do the flush but they need to remove the above components, and replacing them with new ones will not be very labor intensive.
To answer your question, the expansion valve, as the name implies causes the liquid refrigerant to expand into gas in the evaporator, so that the expansion process cools the airflow through the evaporator cores. It controls the liquid to gas conversion, so the evaporator core never freezes.
The replacement compressor comes with the clutch and pulley and if you select the correct one, it will come with the correct size pulley. It is plug and play. I recommend genuine Denso brand, as the cheap ones tend to have quality issues.
If the compressor is seized, then there is really no need to check the voltage on the compressor. It is dead, and the coil fuse is opened to disengage the pulley from the clutch, to prevent belt damage.
