Fan works in high speed only, replaced control panel, no change.the compressor will not operate, replaced compressor relay and clutch relay, no change any help!!!!!!!

My information shows that the 2001 tahoe uses a fan clutch and does not any electric fan. There could be exceptions, but if this is an add on aftermarket fan, there would be some type switch with a relay or fuse wired in the system. First make sure that the radiator is not partly restricted. Using a inferred thermometer check to see is all the radiator tubes are the same temp. Most of the time, the lower tubes are cooler because they are restricted. Also make sure the fan clutch is good. After driving it and the engine is at running, shut the engine off and watch how many times the fan rotated. It should stop after several revolutions.

DTC P0480: Cooling Fan Relay 1 Control Circuit
Circuit/System Description
The engine control module (ECM) commands the fans ON in high speed or low speed. In low speed, the fans are configured in series. In high speed, the fans are configured in parallel.
In low speed operation, the ECM applies ground to the coil side of the low speed relay. Voltage is applied directly to the left cooling fan through the switch side of the low speed relay. The right fan is connected in series to the left fan through the de-energized series/parallel relay, which is the FAN CNTRL relay, so that both fans operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the low speed relay, the series/parallel relay, and the high speed relay. Voltage is applied directly to the right cooling fan through the switch side of the high speed relay. The left cooling fan obtains voltage through the low speed relay and ground through the series/parallel relay.
When the ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding a fan relay OFF, the voltage of the control circuit should be high, near battery voltage. If the ECM detects that the actual voltage of the relay control circuit is different than the expected voltage, DTC P0480 or P0481 will set and the affected ECM driver will be disabled.

Conditions for Setting the DTC
• An improper voltage level has been detected on the cooling fan relay control circuit.
• The condition must be present for a minimum of 30 seconds.

Circuit/System Testing
Ignition OFF, disconnect the 3 cooling fan relays listed below.
• FAN LO relay
• FAN CNTRL relay
• FAN HI relay
Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 85 of each relay and ground.
? If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
Verify that a test lamp does not illuminate between the ignition circuit terminal 85 and the control circuit terminal 86 of each relay.
? If the test lamp illuminates, test the control circuit for a short to ground. If the circuit test normal, replace the ECM.
Remove the test lamp.
Ignition ON, command the affected relay ON using a scan tool. Verify the affected scan tool FC Relay Control Ckt. Short Volts Test Status Parameter is OK.
• For the FAN LO relay, use the scan tool Fan Relay 1 command.
• For the FAN CNTRL and FAN HI relays, use the scan tool Relay 2 and 3 command.
? If not the specified value, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
Install a 3A fused jumper wire between the control circuit terminal 86 and the ignition circuit terminal 85. Command the affected relay ON with a scan tool. Verify the scan tool Relay Control Ckt Short Volts Test Status Parameter is Fault.
? If not the specified value, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
If all circuits and the ECM test normal, replace the affected relay.

Take it to a qualified repair shop that has diagnostic information (shop manual ) An has a professional scan tool . Changed what sensor ? Coolant temp ? You don't guess an just replace parts . Doing a full vehicle scan ,checking for DTC'S in all the modules on the vehicle.

ENGINE HOT A/C OFF
Refer to Cooling System Description and Operation
Do the radiator cooling fans work ?
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 receive positive voltage from the cooling fan relays which 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 the Fan 1 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 Series/Parallel relay, which is 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 grounds the high speed fan relay, which is Fan 3 Relay and the Series/Parallel relay 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 high speed fan relay coil is energized, the relay contacts close to provide battery positive voltage from the 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.
When the requests 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

DTC P1258: Engine Coolant Overtemperature - Protection Mode Active

Possible bad fuse, relay or switch.

Your vehicle cooling fan's are controlled by three relay's , couple of fuse's an the PCM - engine computer . The engine coolant temp. sensor is a input to the PCM , when engine temp get's to 212 the PCM will turn on the cooling fans in low speed . Checking to see what the actual temp is with a scan tool an a infrared thermometer at the thermostat housing ,an looking up the specification's in a service repair manual is how to diagnose . Not guessing an replacing parts . Plus learning how the cooling fan's work .
Relay Driven Dual Cooling Fan Diagnostics Reading factory service info as to how they work also would be a good idea .

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.

The PCM regulates voltage to the coolant fan relays, which operate the fans. Refer to Engine Controls.

Engine Cooling Fan Description - Electric
The electric cooling fans are used to lower the temperature of the engine coolant flowing through the radiator. They are also used to cool the refrigerant (R-134a) flowing through the A/C condenser.
Operation
The electric cooling fan operates when the engine cooling temperature exceeds a certain value. The cooling fan on this engine is controlled by the PCM. The cooling fan has one speed. The PCM turns the cooling fan ON by grounding the coil of the cooling fan relay when certain conditions are met. When the A/C is requested, the cooling fan will also be turned ON.
Power for the cooling fan motors are supplied through Cool Fan #1 and Cool Fan #2 relays. The cooling fan relays are energized when current flows from the fuses in the Cell 23: Cooling Fan Controls , and through the relay coils to ground through the PCM. The Low Speed fans control circuit is grounded for low speed fans operation. During low speed fans operation, both fans run at a slow speed. The High Speed fans control circuit is grounded for high speed operation. During high speed fans operation, both fans run at high speed.
Important: When certain Diagnostic Trouble Codes (DTCs) are present, the PCM may command the cooling fans to run all the time. It is important to perform Powertrain On Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.
If a problem that involves the low speed cooling fan relay control circuit exists, DTC P0480 should set. If the problem affects the high speed cooling fan relay control circuit, DTC P0481 should set. A problem with the ECT sensor should set DTC P0117, P0118, P1114, or P1115. Any of these DTCs will affect cooling fan operation and should be diagnosed before using the Cooling Fan Diagnosis tables. The Cooling Fan Diagnosis tables should be used to diagnose the PCM controlled cooling fans only, if a DTC has not set.

The engine coolant temperature (ECT) sensor (3) is a thermistor, a resistor which changes value based on temperature, mounted in the engine coolant stream. Low coolant temperature produces a high resistance (100,000 ohms at -40°C) (-40°F), while high temperature causes low resistance (70 ohms at 130°C) (266°F).
The PCM supplies a 5 volt signal to the ECT sensor through a resistor in the PCM and monitors the terminal voltage. Since this forms a series circuit to ground through the ECT sensor, high sensor resistance (low temperature) will result in high PCM terminal voltage. When the resistance of the ECT sensor is low (high temperature), the terminal voltage will be drawn lower. This terminal voltage indicates engine coolant temperature to the PCM.
A hard fault in the ECT sensor circuit should set either a DTC P0117 or P0118. Remember, these DTCs indicate a malfunction in the engine coolant temperature circuit, so proper use of the DTC table may lead to either repairing a wiring problem or replacing the sensor, to properly repair a problem.

The engine coolant sensor is an input to the PCM , Two wire's both go to the PCM .An the PCM turns on the cooling fans !

DTC P0480 Cooling Fan Relay 1 Control Circuit
DTC P0481Cooling Fan Relay 2 Control Circuit
The Body Control Module (BCM) request the cooling fans. The BCM sends a Class 2 message to the PCM in order to enable the fans based on various inputs. Thebattery voltage travels to all three cooling fan relay coils. The PCM enables cooling fan relay #1 by providing the ground path. The PCM enables cooling fan relays #2 and mode control together by providing a ground path. The left and right cooling fans are connected in series. This will enable both fans on low speed when the fan #1 relay is energized. When all three fan relays are energized, both fans will operate at high speed. The high speed is possible because the fan relays are wired in a parallel circuit. When the PCM detects that certain DTCs are set, the PCM will enable the cooling fans.
The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set.

Important: A short to ground will cause an open fuse(s). Before performing this diagnostic procedure, inspect the fuse(s) for an open.
1
Did you perform the Instrument Cluster System Check?
--
Go to Step 2
Go to Instrument Cluster System Check
2
Turn the ignition switch to the ON position.
With the scan tool select Instrument Panel Cluster, Special Functions, Instrument Panel Cluster (IPC) gauges.
Perform the Coolant Gauge Sweep Test.
Does the coolant temperature gauge complete a full sweep when commanded?
--
Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls
Go to Step 3
3
Replace the instrument cluster. Refer to Instrument Cluster Replacement .
Did you complete the repair?
--
Go to Instrument Cluster System Check
--

Your best bet would be to take your vehicle to a qualified repair shop that knows how the system works . An has the tools to diagnose the problem .

Under normal operation, in low speed, only the LH fan is initially in operation. Voltage is supplied to the low speed cooling fan relay through circuit 60 BK/LG wire. When the relay is energized, voltage fed to the LH cooling fan motor through circuit 538 GY/RD wire. Ground for the cooling fan is through circuit 57 BK wire. After the LH fan has been energized for 5 -10 seconds the RH fan will start automatically. Voltage is applied to the RH fan motor through circuit 3829 LB/BK wire. BK wire circuit 57 is also the ground.
Under normal operation in high speed both fans should operate from the high speed cooling fan getting a command voltage on circuit 30 BK/LG wire. The relay energizes both fans through circuit229 RD/OG wire while the low speed fan relays are de-energized.
The fans will come on immediately when the airconditioning compressor clutch is engaged mode and when the vehicle is in Drive. OBD-II trouble codes are P0480 low fan 1circuit, P0481 hi fan circuit & P0482 medium fan circuit.

The cooling fan is supposed to come on when the /ac compressor clutch cycles on, and off when it cycles off.
The idle speed kicks up to compensate for the additional a/c compressor load and the additional alternator load. usually, just the low speed comes on until it hits a much higher temperature.

the system should cycle 4 to 7 times/minute at 79 degrees F.

Here are some things to consider:(The PCM (engine computer) is NEVER defective, don't replace it). I don't think it is the ECT (engine coolant temp sensor) or the Cylinder Head Temp Sensor. Or the VSS or the MAF sensors.


The electronically controlled fan clutch is controlled by the powertrain control module (PCM) based upon requests for airflow to cool the engine, transmission and A/C condenser. If no cooling is required, the electronics permit the fan to spin at a slower speed yielding improved fuel economy.
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Inoperative or damaged:

• Electronically actuated fan clutch
• Electronically actuated fan clutch controller
• Wiring, connectors, relays or modules
• Engine Coolant Temperature (ECT) sensor (4.0L SOHC)
• Cylinder Head Temperature (CHT) sensor (4.6L [3V])
• Mass Air Flow (MAF) sensor
• Vehicle Speed Sensor (VSS)
• ----------------------------------------------------------------------------

If the cause is not visually evident, connect the scan tool to the Data Link Connector (DLC).
Retrieve any DTC Codes (Diagnostic Test Code). Autozone will do for free.

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The cooling fan clutch actuator valve controls the fluid flow from the reservoir into the working chamber. Once viscous fluid is in the working chamber, shearing of the fluid results in fan rotation.

The cooling fan clutch actuator valve is activated with a pulse width modulated (PWM) output signal from the powertrain control module (PCM). By opening and closing the fluid port valve, the PCM can control the cooling fan clutch speed. The cooling fan clutch speed is measured by a Hall-effect sensor and is monitored by the PCM during closed loop operation.

The PCM optimizes fan speed based on engine coolant temperature (ECT), engine oil temperature (EOT), transmission fluid temperature (TFT), intake air temperature (IAT), or air conditioning requirements. When an increased demand for fan speed is requested for vehicle cooling, the PCM monitors the fan speed through the Hall-effect sensor. If a fan speed increase is required, the PCM outputs the PWM signal to the fluid port, providing the required fan speed increase.

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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).

The A/C pressure switch is located in the high pressure line (the skinny one) on the passenger side of the engine compartment just under the fuse/relay box. The switch has three functions: <28 psi, the switch opens to protect the compressor from lack of lubrication. >220 psi, the switch shifts the radiator and compressor fan to high speed. >455 psi, the switch opens to protect the compressor seals. Check to see if you have any powertrain DTC's first. A faulty engine coolant temp sensor can cause problems with the compressor clutch relay. If the radiator and compressor fan come on with the A/C on but the compressor clutch does not operate, check the compressor clutch relay. You can also obtain Heater control panel diagnostic trouble codes (DTC's) by turning the ignition switch on. Then turn fan switch off. Press recirc button to select recirc air. Press and hold recirc to turn off recirc air but this time continue to hold the button down until recirc light comes on for two seconds and then goes off. If there is any trouble, the recirc light will then blink a code (if no trouble, the light will remain off) 1 blink = problem in air mix control motor circuit. 2 blinks = a problem in mode control motor circuit. 3 blinks = a problem in evaporator temperature sensor circuit. (this one could be a factor in your case) Turn the ignition switch off to end the test.