Where is the switch that triggers the high speed cooling fan relay?

If you make a jumper wire and jump the load side of the relay and the fans work, it might be the relay or it might be the control side of the relay not getting the signal from the temperature switch. If you jump the load side and the fans don't work it's either the fan motors or a wiring issue between the relay and the fans.

No switch - the radiator cooling fans are controlled by the PCM which receives a signal from the coolant temperature sensor located at the passenger side end of the engine at the lower right.

Possible bad fuse, relay or switch.

ENGINE HOT - AC OFF
Cooling System Description and Operation

you must have a cooling system problem of some sort !

Do the cooling fans come on when A/C is switched on ? Fan's should come on ! Does your vehicle have two or three cooling fan's ?
Cooling Fan Control - Two Fan System
The engine cooling fan system consists of 2 puller type electrical cooling fans and 3 fan relays. The relays are arranged in a series parallel (S/P) configuration that allows the engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block. The ground path is provided at G104.
During low speed operation, the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the low fan fuse 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 S/P relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. After a 3 second delay, the ECM supplies a ground path for the high speed fan relay and the cooling fan S/P relay through the high speed cooling fan relay control circuit. This energizes the cooling fan S/P relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time, the high speed fan relay coil is energized closing the relay contacts, and provides battery positive voltage from the high fan fuse on the cooling fan motor supply voltage circuit, to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.
The ECM commands the low speed cooling fans ON under the following conditions:
• Engine coolant temperature exceeds approximately 94.5°C (202°F).
• A/C refrigerant pressure exceeds 1447 kPa (210 psi).
• After the vehicle is shut OFF, if the engine coolant temperature at key-off is greater than 101°C (214°F), the low speed fans will run for a minimum of 60 seconds. After 60 seconds, if the coolant temperature drops below 101°C (214°F), the fans will shut OFF. The fans will automatically shut OFF after 3 minutes, regardless of coolant temperature.
The ECM commands the high speed fans ON under the following conditions:
• Engine coolant temperature exceeds approximately 104.25°C (220°F).
• A/C refrigerant pressure exceeds approximately 1824 kPa (265 psi).
• When certain DTCs set
At idle and very low vehicle speeds the cooling fans are only allowed to increase in speed, if required. This ensures idle stability by preventing the fans from cycling between high and low speed.
Cooling

Having a qualified professional technician check it out would be your best bet ! Hooking up a factory or professional type scanner an check data input's an DTC'S - diagnostic trouble codes .

Diagnostic Starting Point - Engine Cooling
Begin the system diagnosis with the diagnostic system check. Refer to Diagnostic System Check - Vehicle . The Diagnostic System Check - Vehicle will provide the following information:
• The identification of the control modules which command the system
• The ability of the control modules to communicate through the serial data circuits
• The identification of any stored DTCs and their status
The use of the Diagnostic System Check - Vehicle will identify the correct procedure for diagnosing the system and where the procedure is located.

DTC P0480: Cooling Fan Relay 1 Control Circuit
DTC P0481: Cooling Fan Relay 2 Control Circuit
DTC P0480: Cooling Fan Relay 1 Control Circuit
DTC P0481: Cooling Fan Relay 2 Control Circuit
DTC P0691: Cooling Fan Relay 1 Control Circuit Low Voltage
DTC P0692: Cooling Fan Relay 1 Control Circuit High Voltage
DTC P0693: Cooling Fan Relay 2 Control Circuit Low Voltage
DTC P0694: Cooling Fan Relay 2 Control Circuit High Voltage
DTC P1258: Engine Coolant Overtemperature - Protection Mode Active
DTC P2600: Auxiliary Coolant Pump Relay Control Circuit
DTC P2601: Auxiliary Coolant Pump Performance
DTC P2602: Auxiliary Coolant Pump Relay Control Circuit Low Voltage
DTC P2603: Auxiliary Coolant Pump Relay Control Circuit High Voltage

Why ? Did you test ? Hook up a scan tool to see if the PCM/ECM - engine computer is reading coolant temp. ? Testing not guessing ? Do you even know how the system works .

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block.
During low speed operation, the ECM supplies the ground path for the low speed fan relay, which is Fan 1 Relay, through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from Fan 1 Fuse 29 through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the Series/Parallel relay, which is the Fan 2 Relay, and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. The ECM supplies a ground path for the high speed fan relay, which is the Fan 3 Relay, and the Series/Parallel through the high speed cooling fan relay control circuit. This energizes the Series/Parallel relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the Fan 3 Relay coil is energized, the relay contacts close to provide battery positive voltage from Fan 2 Fuse 33 on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.
When the request for fan activation is withdrawn, the fan may not turn OFF until the ignition switch is moved to the OFF position or the vehicle speed exceeds approximately 10 mph. This is to prevent a fan from cycling ON and OFF excessively at idle.

Cooling fan switch ? The cooling fans (2) on that motor are controlled by three relays . A coolant temp. sensor gives temp info to the PCM - engine computer .
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 S/P relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 2 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan S/P relay coil is energized closing the relay contacts and provides battery positive voltage from the cool fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.
The PCM commands Low Speed Fans on under the following conditions:
• Engine coolant temperature exceeds approximately 106°C (223°F).
• When A/C is requested and the ambient temperature is more than 50°C (122°F).
• A/C refrigerant pressure exceeds 1 310 kPa (190 psi).
• After the vehicle is shut off if the engine coolant temperature at key-off is more than 140°C (284°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.
The PCM commands High Speed Fans on under the following conditions:
• Engine coolant temperature reaches 110°C (230°F).
• A/C refrigerant pressure exceeds 1 655 kPa (240 psi).
• When certain DTCs set .
Watch this video ,it shows how it works !
Relay Driven Dual Cooling Fan Diagnostics

Are the fans running on low or high ?
Circuit/System Description
The engine control module (ECM) commands the fans ON in either high speed or low speed, depending on cooling requirements. In low speed, both fans are turned ON at a reduced speed. High speed has both fans turned ON at full speed.
In low speed operation, the ECM applies ground to the coil side of the fan low relay. This energizes the coil and applies voltage directly to the left cooling fan through the switch side of the fan low relay, which is fed by the fan 1 fuse. The right fan is connected in series to the left fan through the de-energized fan control relay so that both operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the fan low relay, the fan control relay , and the fan high relay. On the fan high relay, the energized coil closes the switch side of the relay and applies voltage directly to the right cooling fan through the switch side of the relay, which is fed by the fan 2 fuse. At the same time, the ECM energizes fan control relay pulling the switch side over, providing a direct path to ground for the left cooling fan, which has voltage applied through the energized fan low relay. In high speed mode, the fans are operated as a parallel circuit with full voltage applied to each.
You should have it hooked up to a scan tool that can read engine sensor data parameters . Check for DTC'S - diagnostic trouble codes etc...
Circuit/System Verification

1. If DTCs P0480 or P0481 are set, perform those diagnostics first.
2. Ignition ON, verify with a scan tool that the control module is not commanding fan activation.
3. Ignition ON, observe that the fans are not activated.

Your best bet is to take it to a ASE certified repair shop !

The engine cooling fan system consists of 2 electrical cooling fans and 3 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 from the underhood accessory wiring junction block. The ground path is provided at G113. The relays are located in the underhood fuse / relay box .
So ,what's the problem Paul , car overheating ? Fans not working ?
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 from the cool fan 1 fuse through the cooling fan motor supply voltage circuit to the right cooling fan. The ground path for the right cooling fan is through the cooling fan 2 relay and the left 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 2 relay coil, closes the relay contacts, and provides a ground path for the right cooling fan. At the same time the cooling fan 3 relay coil is energized closing the relay contacts and provides battery positive voltage from the cool fan 2 fuse on the cooling fan motor supply voltage circuit to the left 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 PCM commands Low Speed Fans on under the following conditions:
?€¢
Engine coolant temperature exceeds approximately 106?°C (223?°F).

?€¢
When the A/C is requested and the ambient temperature is more than 50?°C (122?°F).

?€¢
A/C refrigerant pressure exceeds 1310 kPa (190 psi).

?€¢
After the vehicle is shut off if the engine coolant temperature at key-off is greater than 140?°C (284?°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.

The PCM commands High Speed Fans on under the following conditions:
?€¢
Engine coolant temperature reaches 110?°C (230?°F).

?€¢
A/C refrigerant pressure exceeds 1655 kPa (240 psi).

?€¢
When certain DTCs set.

So

alldata.com
question one, is what engine.
diffr, engines use different cooling, systems.

The thermostat may be stuck. If it dosent open then the engine will overheat. If you turn the ac on then the air rushing around the engine will help cool it down. Replace the thermostat and it should fix it