Morning all,,

Could some one advise me as to where I would find the relays that control the front electric fan on my l322 v8 petrol, as I need to check if these are working before I shell out for a new front fan assembly.

many thanks \\

The heater blower fan or the engine cooling fan?

Dan 

dan_uk_1984 wrote:

The heater blower fan or the engine cooling fan?

Dan

From what I read in RAVE the auxiliary fan is directly controlled by the ECU:

Engine Cooling Fan Control
The engine's electric cooling fan is controlled by the ECM. When the compressor is engaged the ATC ECU sends a fan speed message between 0 (off) and 15 (maximum speed) to the ECM, via the K bus, instrument pack and CAN bus. The ATC ECU requests the cooling fan on when:
The vehicle speed is less than 44 mph (70 km/h)
There is no fault with the compressor clutch circuit
Battery voltage is less than 16 V.
The fan speed requested depends on the pressure in the refrigerant system. The higher the pressure the faster the fan speed that is requested. When vehicle speed increases to more than 50 mph (80 km/h) the ATC ECU changes the fan speed request to 0 until vehicle speed decreases to less than 44 mph (70 km/h) again.

adara wrote:

ECU changes the fan speed request to 0 until vehicle speed decreases to less than 44 mph (70 km/h) again.

I imagine it will be a stepper resistor, similar to the blower final stage resistor. In which case it will usually fail at 1 or 2 speeds but will still work at others.

The fan doesn't actually do much other than cool the A/C condenser, and even then only at low speeds. What is the actual problem you're having?

Regards,

Dan 

Actually did anyone see their auxiliary fan spinning? I never saw mine turn, even while using the A/C on a hot day... How can one check it?

Just depends on refrigerant pressure (I imagine TestBook can test it though?). Under normal driving the fan shouldn't need to come on, but maybe on a 30 degree day in full sun with the A/C on max I've heard it flick on whilst in stationery traffic.

Don't forget the system is multi-climate. So it should worth fine in Sahara or South Kensington, so a lot of the time the aux fan is not required.

Dan 

On most (all) of the cars I owned the electric fan started turning when A/C was enabled while stationnary. Not on the RR.
There is a very intriguing info in RAVE:

"To protect the system from extremes of pressure, the ATC ECU disengages the compressor clutch if the pressure:
Decreases to 1.9 ± 0.2 bar ( 27.5 ± 3 lbf/in 2 ): the ATC ECU engages the compressor clutch again when pressure increases to 2.8 ± 0.2 bar (40.5 ± 3 lbf/in 2 )
Increases to 33 ± 1 bar (479 ± 14.5 lbf/in 2 ): the ATC ECU engages the compressor clutch again when pressure decreases to 23.5 ± 1 bar (341 ± 14.5 lbf/in 2 )"

33bar!!! That's a lot of pressure!

adara wrote:

On most (all) of the cars I owned the electric fan started turning when A/C was enabled while stationnary. Not on the RR.
There is a very intriguing info in RAVE:

"To protect the system from extremes of pressure, the ATC ECU disengages the compressor clutch if the pressure:
Decreases to 1.9 ± 0.2 bar ( 27.5 ± 3 lbf/in 2 ): the ATC ECU engages the compressor clutch again when pressure increases to 2.8 ± 0.2 bar (40.5 ± 3 lbf/in 2 )
Increases to 33 ± 1 bar (479 ± 14.5 lbf/in 2 ): the ATC ECU engages the compressor clutch again when pressure decreases to 23.5 ± 1 bar (341 ± 14.5 lbf/in 2 )"

33bar!!! That's a lot of pressure!

You also have the viscous fan constantly pulling air in though, so this is generally why other (lesser) cars have to have the condenser fans running all the time. On smaller cars this puts a significant load on the alternator, coupled with the compressor that’s why it’s more economical to leave the a/c off. On the RR however most of the time you’re only running the comp’ which on an engine of this size is next to nothing. That and the fact that the A/C should be left on all year round to dehumidify the interior to prevent electrical gremlins.

The pressure quoted above equates to how cold the evaporator is, so when its high pressure there is no need for the comp’ to be running or too much ice may form (also if ice does form the pressure will increase, it cuts out and then it defrosts) That’s why it cycles on and off.

Dan 

dan_uk_1984 wrote:

adara wrote:

ECU changes the fan speed request to 0 until vehicle speed decreases to less than 44 mph (70 km/h) again.

I imagine it will be a stepper resistor, similar to the blower final stage resistor. In which case it will usually fail at 1 or 2 speeds but will still work at others.

The fan doesn't actually do much other than cool the A/C condenser, and even then only at low speeds. What is the actual problem you're having?

Regards,

Dan

I never saw my electrical fan spinning and after a frontal collision I had a new bumper and fan installed and I can tell you the new one isn't spinning either. The new fan is definitely OK and the dealer swears the diagnose shows no errors but I'm convinced something is wrong. As the fan is controlled directly by the ECU (no relay), there is really no other element to be blamed, except for the pressure sensor on the A/C maybe, but as the compressor clutch is disengaging I suppose that one works. It's cold now here, but already the A/C pipe is hot and the fan is not spinning.

I was just checking all my fluid levels when i notice several disconnected wires on the front offside of the radiator. I plugged them all back together and found that they ended up on a small black plastic box attached to the radiator ousing and the plastic clip was broken attaching it to the housing. Guessing this is the wiring for the electric fan and no idea how long it has been disconnected. Never had an overheating problem yet but I have had to put in about 5 litres of coolant since my alternator got replaced in December. Here's hoping it was only an air lock (fingers nervously crossed).

That's just the pollution sensor. It doesn't control the fan.