Last update:

10/01/2006

  Coolant Fans

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Cooling Manual

 

Coolant Fans Circuit

All Scorpios made between 1994 and 1998 achieve the cooling of the radiator by means of an electrical two speed twin fan system. Unlike other cars (for example the Mercedes W124), the same fans are also used to cool down the condenser while the air conditioning system is running. Depending on the engine type, the fans can be controlled either by a thermal switch mounted on the radiator (2.9 12V or 2.5 TD), or by the PCM (DOHC2.0 8V and 16V, DOHC2.3, Cosworth 2.9 24V).

One point should be clear right from the beginning: both fans must either run simultaneously or not run at all. You should never have only one running fan.
Also, the fans only work while the engine is running. They must never stay on after stopping the engine, like in other cars (e.g. some Renaults).

Since the cooling fans are also used for air conditioning, they run on low speed whenever the A/C is on, regardless of the engine temperature. If they run on high speed with the A/C on while the engine is cold, this indicates a refrigerant pressure problem.

The fans work as follows:

Engine stopped => both fans off
Engine cold, A/C off => both fans off
Engine cold or warm, A/C on => both fans running on low speed
Engine hot, regardless of A/C => both fans running on high speed

With an OBD lead you can see what the PCM is currently ordering the fans to do. On the Enhanced page there are two PIDs: LFC (low speed fan command) and HFC (high speed fan command). If LFC is ON, the fans should be running on low speed. If HFC is ON, the fans should be running on high speed.
Youll notice that the high speed command does NOT cancel the low speed command. As long as the conditions for low speed are met, low speed command stays on even if high speed has come on in the meantime. When we look at the relay diagram well see that this has actually no practical meaning.

The PCM controls the fans by means of a relay, located in the engine compartment. The FINIS code of the relay is 1-030-495.
 

12V AND DIESEL MODELS

Owners of the 12V and 2.5 TDi diesels will find a three-way switch (Normal, Temp 1 and Temp 2) and these instructions do not apply to them. The circuit is the same but uses the switch instead of the PCM.

EECV MODELS

For the EECV-equipped cars, (the two DOHC 2.0L models, the 2.3L and the 24V) there is no temperature switch.  In fact the fans are connected in series in usual use, sharing six volts each which results in the low speed running.  There is no fan thermister switch - instead the temparture of the coolant is sensed by the EECV Powertrain Control Module via the ECT.

The following is an explanation of the coolant fans circuit.

FANS ON LOW SPEED OPERATION

On the above diagram you can see the wiring path that is used when the fans run in slow speed.

 

On the right hand side of the circuit you can see there is a permanent supply through fuse 39 into the first fan. The relay is open so both fans are off.

 

When the PCM wants the fans to run slow it energises the relay by grounding pin 68 to earth. The relay has a switched live feed to its coil from the ignition switch. This prevents the fans coming on if the ignition is off.

 

When the relay is energised the contacts close and the two fans are connected in series.  This means that the 12v supply is split evenly between the 2 fans and so they get 6v each.  This is what makes the fans turn slowly.

 

This diagram is for all cars except 2.9 12v and diesel. They have a 3 way temp switch, Normal, Temp1, Temp2. The circuit is the same but uses this switch instead of the PCM.

 

FANS ON HIGH SPEED

 

The above diagram is for FAST SPEED. It is basically the same as before but note each fan has its own fuse and the relay is switching fan 1 direct to earth and is switching 12v to fan 2.


Each fan now has 12v across its terminals and runs at maximum speed. The PCM grounds pin 17 to activate the fast speed.

One interesting point is worth noticing here. When the fans run on low speed they are connected in series, which means they cannot run independently from one another. If one of the fans is not working due to some electrical problem, then the other one wont work either. However, on high speed they are connected in parallel, so even if one fan does not work the other one will. If one fan stops running for mechanical reasons (a worn out bearing, for example) but the electrical connections are OK, the other fan will continue to run even in low speed mode, but it will receive more than 6V, so it will run faster than supposed to, probably at almost full speed.

You can use the OBDII cable and software to monitor the PCM outputs to the fan relay whilst you are driving and you can see if they are being commanded to run slow or fast.

 

Fuses

Fuse no. 37 controls the energizing and de-energizing of the relay. If it burns out, both fans will always be off, since the PCM will have no way of turning them on, neither on low speed nor on high speed.

Fuse no. 39 controls both fans on low speed and the first fan on high speed. If it burns out, none of the fans will work on low speed, and only the second fan will work on high speed.

Fuse no. 44 controls the second fan on high speed. If it burns out, both fans will work on low speed, but only the first fan will work on high speed.

 

Component location

All three fuses are located in the auxiliary fuse box, next to the battery.

The relay, which is long (much bigger than common relays) and dark green coloured, can be found in the engine compartment, immediately behind the right hand headlight. Its attached by means of a screw.

The first fans plug is located below the fan, very close to it, and can only be accessed from beneath the car, after removing the undertray.

The second fans plug is located near the fan and to the right (as seen from the front to the back of the car). It can be easily accessed without raising the vehicle, but you have to remove the resonator box first.
 

SYMPTOM
 

Neither fans run at all

Check fuse F37

Check Fans relay R34

Check Fans multiplug for 6V and Ground

Check ECT (Engine Coolant Temp sensor) for varying resistance - lower when hot (see ECT and Data) note: ECT does not provide voltage for instrument panel engine temp gauge - this is a separate sensor

 

Only one fan runs at high speed when hot

Check Fuse F44 and F39

Check wiring and multiplugs

Check fan not running for 12V and Ground

 

 

 

 

 

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