Fresh Air Inspector
Member
- Joined
- Nov 4, 2018
- Location
- LaHave, Nova Scotia, Canada
Hello All,
The electric cooling fan on my 1994 940 is staying on after the car is shut down. I've traced the problem to a bad low pressure switch (bottom of the AC condenser). Pity as it's less than 2 years old.
As a stop gap I've unplugged the low pressure switch. Being winter here in the Great White North (aka Canada), I don't believe it will adversely affect the AC performance (only kicks in during Defrost cycle) or the cooling system temperature.
My understanding of how the cooling fan operates is as follows;
Engine Cooling
If the temp sensor in the cylinder head is triggered the ECU switches on the cooling fan. I assume this is high speed mode.
AC Cooling
The cooling fan is triggered by the pressure in the AC system. This is linked to the AC compressor engaging and/or the rise in R134a pressure in the system. Where I draw a blank is the purpose of the low and high pressure switches in the condenser.
So, hopefully someone can help me to understand how the low and high pressure switches function in relation to the cooling system as well as the AC system.
As always, any insight will be appreciated.
The electric cooling fan on my 1994 940 is staying on after the car is shut down. I've traced the problem to a bad low pressure switch (bottom of the AC condenser). Pity as it's less than 2 years old.
As a stop gap I've unplugged the low pressure switch. Being winter here in the Great White North (aka Canada), I don't believe it will adversely affect the AC performance (only kicks in during Defrost cycle) or the cooling system temperature.
My understanding of how the cooling fan operates is as follows;
Engine Cooling
If the temp sensor in the cylinder head is triggered the ECU switches on the cooling fan. I assume this is high speed mode.
AC Cooling
The cooling fan is triggered by the pressure in the AC system. This is linked to the AC compressor engaging and/or the rise in R134a pressure in the system. Where I draw a blank is the purpose of the low and high pressure switches in the condenser.
So, hopefully someone can help me to understand how the low and high pressure switches function in relation to the cooling system as well as the AC system.
As always, any insight will be appreciated.