Where is the relay for the motor cooling fan?

If you're experiencing issues with the cooling fan relay in your 1998 Plymouth Voyager, there could be several reasons behind it. The cooling fan relay is responsible for controlling the operation of the cooling fan, which helps regulate the engine temperature by dissipating heat.
Here are some common reasons why the cooling fan relay might be causing problems:

1. Relay Failure: Over time, relays can wear out or become damaged due to electrical faults or excessive heat. If the cooling fan relay has failed, it may not properly engage the cooling fan when needed, leading to overheating.
2. Electrical Issues: Faulty wiring or connections can disrupt the flow of electricity to the cooling fan relay, preventing it from functioning correctly. Inspect the wiring harness and connections for any signs of damage or corrosion.
3. Temperature Sensor Malfunction: The cooling fan relay is often triggered by signals from the engine's temperature sensor. If the sensor is faulty or sending incorrect signals, it may not activate the cooling fan relay when necessary.
4. Faulty Cooling Fan Motor: If the cooling fan motor itself is defective or worn out, it may not respond to signals from the relay, even if the relay is functioning correctly. Check the cooling fan motor for any signs of damage or wear.
5. Blown Fuse: In some cases, a blown fuse can cause the cooling fan relay to malfunction. Check the fuse box for any blown fuses related to the cooling fan system and replace them if necessary.

To diagnose the exact cause of the issue, you may need to perform some electrical tests or consult a mechanic with experience in automotive electrical systems. They can use diagnostic tools to pinpoint the problem and recommend the appropriate repairs or replacements.

Usually a bad relay. See this post on GM relays and cooling fans

https://ricksfreeautorepairadvice.com/car-overheating/

get a multi- meter so you can test the fan and coolant sensor

A/C Off For Engine Protection
Refer to Cooling System Description and Operation

DTC P1258: Engine Coolant Overtemperature - Protection Mode Active.
This is something you need to take to a qualified 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) or 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 junction block. The ground path is provided at G100.
During low speed operation, the PCM/ECM 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 maxifuse® 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 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/ECM 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/ECM supplies a ground path for the cooling fan 2 relay and the cooling fan relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 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 from the cool fan 2 maxifuse® 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 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 fuse block.
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 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 PCM 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 PCM 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 there own ground path. The result is a parallel circuit with both fans running at high speed.
Your best bet would be to take your vehicle to a qualified repair shop !
Relay Driven Dual Cooling Fan Diagnostics

In the engine compartment fuse block. Look at positions 7 and 8. There should be a diagram under the lid.

Replace the fan relays. The Radiator Cooling Fan Motor Relay is located: Under hood, driver side, front side of strut tower, mounted in relay panel
Application:
High speed The Radiator Cooling Fan Motor Relay is located: Under hood, driver side, front side of strut tower, mounted in relay panel
Application:
Low speed,here's a new part.
http://www.autozone.com/cooling-heating-and-climate-control/relay-radiator-cooling-fan-motor/duralast-relay-radiator-cooling-fan-motor/plymouth/voyager-2wd/1996/6-cylinders-3-3-0l-mfi/412240_0_0

there is 2 fuses that you have to check
one will be in the big fuse assembly in the engine bay, the other probably in the fuse assembly in the cab
If they prove ok then it is possible that the coolant temperature SENSOR is faulty and needs replacing
don't confuse it with the temperature sender which operates the temp gauge.

Check fuse for cooling fan, check temperature sensor functioning for cooling fan, check relay for the fan (if you have one), check cooling fan motor circuit with resistance check (should read low Ohms, less than 2 Ohms beacause the fan is a powerful motor with 10-20 Amps).
If everything is measured O.K. you should check the wiring. Disconnect the connector at the cooling fan motor, connect a test light to the harness from the car (not to the motor side) and run the engine. Watch the temperature gauge and before you the boiling (overheating) the bulb should lit up. If not you should go back with this test step by step to the relay. The relay can be tested if you can find a same one on your relay board and swap temporary (e.g. swap the AC clutch relay with the cooling fan relay)

fuse #9 protects the 2 cooling fan relays.

It looks like the hgh speed cooling fan realy is in a thin box mounted sideways between the battery and fender.

It has high speed relay, autolamp relay, autolamp headlamp relay, horn relay, washer motor relay, wiper hi/lo relay, wiper park relay.

Section 03-03: Engine Cooling 1999 Taurus, Sable Workshop Manual
DESCRIPTION AND OPERATION Electrical System NOTE: With A/C ON, the cooling fan motors will run continuously. Cooling fan motors will not cycle ON and OFF with A/C clutch (2884) .

NOTE: An exception to this is when vehicle speed is over 61 km/h (38 mph) and coolant temperature is below 100°C (212°F), and A/C head pressure is below 1.71 MPA (250 psi). The cooling fan motors will then automatically shut off.

The cooling fan motors are mounted within a fan shroud (8146) behind the radiator (8005) .

Engine Cooling Fan Control CCRM Applications The PCM monitors certain parameters (such as engine coolant temperature, vehicle speed, A/C on/off status, A/C pressure, etc) to determine engine cooling fan needs. The PCM controls the fan operation through the Fan Control (FC) output (single speed fan applications) or the Low Fan Control (LFC) and High Fan Control (HFC) outputs as shown in Table 2. Although the fan control (FC), low speed fan control and high speed fan control relays are normally open relays, the FC/LFC circuit is wired through a voltage inverter inside the CCRM. The voltage inverter ensures that the PCM must turn on (ground) the FC/LFC output to turn the fan off. This is done so the cooling fan will operate in the event of an open FC/LFC circuit.

Stand-Alone Fan Control Relay Applications The PCM monitors certain parameters (such as engine coolant temperature, vehicle speed, A/C on/off status, A/C pressure, etc) to determine engine cooling fan needs. The PCM determines engine cooling fan control requirements and controls the fan operation through the Low Fan Control (LFC) and High Fan Control (HFC) outputs (Table 3).