how do I know what speed my C5 radiator fans are set at?

how do I adjust to set them to fastest speed?

thanks....

 

Cooling Fan Control

The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. The ground path is provided at G102.


During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.


During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.


The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).

 

well, when it is hot (90 plus) in South Carolina and I am idling in traffic the temp goes over 250*....with the car running at 40 mph steady with no stops it will drop to 215* but I think that is do to air flow into the car and not the fans.....both fans run but it does not seem they are running fast when the car is hot and idling in my drive way and the coolant temp keeps climbing....how can I tell if they are running at low speed or high speed?

 

Best way to really clean your radiator and the A/C condenser is to REMOVE the radiator... you might consider a 160 degree stat for your region during the summer months...

 

had to replace damage air damper (piece of black plastic in front of car) and did the cleaning while it was off....
it has a 160 in it now....when temps below 90 there is no sweat or when A/C is off....

 

SO, you removed your radiator and cleaned it?

 

I would like to install an overide switch for the low and high speed functions. I understand that out of the PCM, number 42 (dark green) is the low speed ground and number 33 (dark blue) is the high speed grownd. Where is the best location to tap into those wires?