Wiring Diagram

[Lemner]

Hello All,
Does anyone have a wiring diagram relating to the radiator fan/ECU please?

[g8dhe]

Yes but which engine ? There different!

[g8dhe]

I've dug both out take your pick! In both cases the relays are controlled by the ECU, in the case of the diesel, you'll note that they are dual speed fans, so don't go round trying to re-wire them as you will likely cause serious problems resulting in a burn-out of the windings!

WL-T - diesel

Petrol engines

[Lemner]

Hello Geoff,
Many thanks for your help with this. I must apologise for only providing half of the information. It is a 2.5 diesel.
In an attempt to draw a line under some overheating issues she has suffered in the past- cracked head in 2017 and gasket failure this year I have nearly finished fitting a Davies Craig EWP 115 system (with help).

The head was replaced in 2017 for a complete kit I bought from AV Leisure which worked splendidly until earlier this year. I believe the gasket may have been inferior, its hard to say. Another thing discovered was sediment in the coolant. I don't think the coolant system was flushed thoroughly enough when the head was changed. A mechanic friend of mine has said the issues in both cases were due to overheating, not helped by a medium sized impeller that has to move a large amount of coolant, and of course sediment.

The set up for the new system includes removal for the thermostat workings to keep the water flowing at all temperatures and removal of the impeller pulley, but retaining the impeller. My thinking is that if an issue arose with the EWP system I could re-fit the pulley and belt and drive with 1 eye on the temperature gauge.
If you are unfamiliar with this EWP system, it pulses the water pump at low speed from startup and monitors the temperature. The rate of water flow is varied as required to keep the temperature as close to the ideal running temperature of the engine as set by the user. If the engine exceeds this temperature when idling or in traffic the system switches the fan in and out to regulate.

The last thing to do is connect the fan switch from the EWP, hence the question. I have read on the forum about the 2 speed fans and intend to connect the fan switch connection to the high speed trigger relay(s) as I think they operate in tandem.

My next question is this- I have read that the fans are come on at low speed when the engine is around 94 C and high speed fans at 108 C. When the fans are at high speed does the low speed relay cut out?

From the wiring diagram you kindly sent, it appears to me that the connection marked with a 15 switches a 12v to both fans via relay B6-01 and a 0v to both fans via relay B6-03. I think this is low speed?
Terminal 16 appears to switch in 12v to both fans- high speed?

Please correct me if I have read this wrong, but I think what I need to do going forward is remove B6-01, by-pass the switching pair of contacts on B6-03 and only use B6-02 to switch the fans on when required?

I would obviously retain these relays if I had to run the engine without the EWP.

Please let me know your thoughts on this, they are greatly appreciated Sir.

Kind regards
Ian

[g8dhe]

B6-03 is used in conjunction with B6-01 for one speed and B6-02 is used for the remaining speed mode.
However I can't say if both sets of relays need to operate or alternate sets.
What I can't be sure of (I don't have a diesel to play/test with!) is which mode the motors are run in, dual wound motors can be wound in a variety of ways and connecting them incorrectly can be disastrous, but I have no information on which mode is used.
I would suggest you monitor the relay coils and see what the ECU uses for the speeds simply put a meter on the coil connections going to the relays diagram points 15 & 16 and see which relay sets operates at which speed, bear in mind that the Air Con also turns on the low speed mode when the Air Con is in use at all times.
When monitoring points 15/16 the voltage will fall from 12v to 0v when the relay operates.

[Lemner]

Many thanks Geoff,
There's a couple of confusing points relating to the workings of these fans.
1- Why isn't the 0v connection on the fans common?
2- Why does relay B6-03 switch a 0v connection into play?

I can only assume that for high power fan working all 3 relays need to be energised unless relays B6-01 and 03 drop out at full fan and the 0v connection for high power is the ground connection marked as 2 from both fans. If that is the case then I just need to apply the EWP 0v connection to the coil of B6-02 to make the fans run at high speed. I could try this and if they burn out buy a set of fans from a petrol.

Am I correct in thinking that the best way to invoke full fan working is to remove the wires on the temperature sensor on the head? this makes the ECU trigger full fan I have read. I cant test low fan working as my air con has never worked.

It might be safer to just get a 2 pole relay applying a 0v connection to connections 15+16 as marked from the ECU, the relay being triggered from the EWP.
Does this sound sensible to you Sir?

The other option available would be to use the EWP fan connection 0v to trigger a relay that shorts the wires to the temperature sensor on the head and fool the ECU into thinking the engine is very hot. I'm not a fan of this approach as the ECU may use this sensor for other purposes and this could have a number of knock-on consequences.

Regards
Ian

[g8dhe]

Right the questions come down to the operation of dual wound motors - they are not obvious unless you have a good understanding. To start with a Motor and a Generator are basically one and the same thing, there differences are down to optimising there operation. Consequently with dual wound motors if only one winding is being powered to operate as a motor, then the other is operating as a generator. If the windings are not connected correctly and adequately isolated then that is where the disaster starts! If the windings are connected in opposition (and the windings are identical) then the magnetic fields oppose each other and cancel out causing a massive current flow from the energising source - flames will ensue if the motor is static at the time. If the motor is running when the connection is made then the motor is likely to be stopped instantly, causing two problems the rotational mechanical energy will have to go somewhere usually involving the mounting points failing rapidly and the device taking to the air! Secondly a magnetic field also contains very significant energy, if the field itself is cancelled then the field lines collapse generating massive voltage spikes in the windings - being close to lighting level arcs is NOT recommended especially when the device is flying thru the air in a random direction!!!

This is why the power connections of one winding are both switched to ensure that the winding is totally isolated as its quite common for leakage currents on brushed motors and there windings.

As to the operation, I honestly can't say, the motors may be designed to work with only one winding powered at a time, or they may equally be designed to operate with both windings either in series or parallel connection hence three different ways of operation. The diagrams and maintenance manuals don't go into the design criteria and hence without having one of my own to play with (and its really not worth playing with these things!!) its just not possible to say what modes of operation are being used.

[Lemner]

Many thanks Geoff,
I'll get the meter out this weekend and see which terminals go to 0v when the fans are running and report back.

Regards
Ian

[Lemner]

Hello Geoff,
I have been reading an earlier post by jimmo62. There's something about it which has confused me. Relay B6-02 has a 40A fuse in series. Logically you would assume that low speed fans would be off the 30A fuse?
Can you shed any light on this please?



Re: Does anyone know how the fans on an auto diesel work?
Post by jimmo62 » Sun Aug 10, 2014 3:34 pm

That seems right and agrees with my tests.

The potentiometer burned out pretty quickly (it was only a low power one....) so I had to use fixed resistors.

With a 330 ohm resistor in place of the temperature sensor and a/c off, none of the relays/fans are on. With the a/c on, relay B6-02 is activated. So that corresponds to low running temp - fan is only on for the a/c. 330 ohms corresponds to water temp around 80C (spec says between 290 ohms and 340 ohms at 80C).

With 150 ohms and a/c off, relay B6-02 is activated. That would correspond to high temperature running.

With a short circuit and a/c off, relay B6-02 is activated and so are relays B6-01 and B6-03 for the high fan speed. That would correspond to well over temp.

[g8dhe]

Motors at low speed can take more current than at higher speeds, remember they are inductors creating a magnetic field not simple resistors.
See here https://www.youtube.com/watch?v=STdONYFI2C4

[Lemner]

Hello Geoff,
I have fully tested the voltage readings at the 3 relays when using a variable resistor at the temperature sensor and can confirm that Jimmo was absolutely correct.
I am very grateful for your help and assistance with this query, without it I may have smoked the fan motors!

Kind regards
Ian