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I was asked recently if i could post up how to change the wiring in a four wire 3 speed diesel control box, this was/is so it could be added to a known good fan motor from a petrol V6 with two wires coming from the motor.
V6 two wire 2 speed fan motor Fig 1
1

Wiring leads will need to be long enough so the black wire is cut after the join Fig 2
2

The red wire long enough with some brown wire showing Fig 3
3

That fan motor can now be set a side to carry out the modified wiring to the diesel four wire 3 speed control box so it will attach to the above two wire 2 speed motor.

You will now need to cut the four wires from the diesel fan motor, this is either because fan motor is not repairable or you are changing over to the above two wire 2 speed fan with gold resistor. Fig 4
4

You will now have in front of you all the wiring & control box of the four wire 3 speed diesel fan, which is going to be modified so it can match up to the two wire 2 speed fan with gold resistor Fig 5
5

This is what the control box looks like in the four wire 3 speed diesel fan, it consists of 6 thick wires, & 4 thin wires, as you can see from the photo below. Fig 6
6

Ok so lets get started in modifying the control box wiring, first remove the green isolator from the box Fig 7/8
7

8

Next step is to pull off the purple wire from the spade/relay Fig 9/10
9

10

This purple wire can now be cut inside the box as it will not be used for the modification Fig 11/12
11

12

This can now be discarded or maybe keep it for future wiring ? i don't like to throw anything away Fig 13
13

Back to the control box the purple wire coming out the the control box can now also be cut Fig 14/15
14

15

That is the thick purple wire taken care of again set the wire to one side for use when ever, Fig 16
16

We now move onto the the thick brown wire which is connected to the relay with the grey wire, grip this with the pliers Fig 17
17

Then pull and remove from the relay Fig 18
18

Next we move to the thick black wire with the this trace wire attached to it, grip and remove this from the first relay Fig 19
19

Move the wire to the second relay and pop it onto there. Fig 20/21
20

21

Ok back to the thick brown wire we removed from that relay earlier, with the pliers cut this wire outside of the box Fig 22/23
22

23

That sorts out the thick brown wire from going into the box Fig 24
24

Cut the same wire from inside the box Fig 25/26
25

This will not be needed now so keep or throw it away Fig
26

The next step is to follow the thick brown wire attached to the large relay backwards Fig 27
27

Follow/trace this back up the loom to where it joins a split section Fig 28
28

You then cut this close to the joint Fig 29/30
29

30

The thick wire now attached to the joint is the one that you first cut from the control box earlier, this will later be spliced to the red wiring coming from the fan motor. Fig 31
31

This thick brown wire is also connected to the main wiring loom plug, which as the thin wires yellow, & blue /red wires attached too Fig 32
32

You /we now need to sort out the thick black wire in the control box with the thin black wire attached Fig 33
33


Follow / trace back along the loom until you find the split joint, Fig 34
34

Now cut the black wire that lead back to the fan motor leaving at least 8cm sticking out of the joint. Fig 35
35

Put that with the other wires you have cut from the control box & loom Fig 36
36

The control box is now ready to have the wire joined up to the loom, the thick brown wire from the large relay Fig 37/38
37

38

Will now have the end stripped back along with the thick black wire coming from the joint on the loom Fig 39
39

Join these together with a good glued based heat shrink connector, i also added some heat shrink to go over the that joint. Fig 40
40

The heat shrink glued connector Fig 41
41

Crimp and join these two wires together Fig 42
42

Seal the joint with a lighter Fig 43/44
43

44

I then slipped over the black heat shrink as a double protector Fig 45
45

Heat shrank that to seal. Fig 46/47
46

47

The thick brown wire in the control box as now become the thick black wire which would be in a control box with a two wire 2 speed fan,
it is marked it with some black all marker pen Fig 48/49
48

49

This then joins into the split connection and onto the thick black wire going to the plug. Fig 50
50

[quote="Arctic"]I was asked recently if i could post up how to change the wiring in a four wire 3 speed diesel control box, this was/is so it could be added to a known good fan motor from a petrol V6 with two wires coming from the motor.
V6 two wire 2 speed fan motor Fig 1
1

Wiring leads will need to be long enough so the black wire is cut after the join Fig 2
2

The red wire long enough with some brown wire showing Fig 3
3

That fan motor can now be set a side to carry out the modified wiring to the diesel four wire 3 speed control box so it will attach to the above two wire 2 speed motor.

You will now need to cut the four wires from the diesel fan motor, this is either because fan motor is not repairable or you are changing over to the above two wire 2 speed fan with gold resistor. Fig 4
4

You will now have in front of you all the wiring & control box of the four wire 3 speed diesel fan, which is going to be modified so it can match up to the two wire 2 speed fan with gold resistor Fig 5
5

This is what the control box looks like in the four wire 3 speed diesel fan, it consists of 6 thick wires, & 4 thin wires, as you can see from the photo below. Fig 6
6

Ok so lets get started in modifying the control box wiring, first remove the green isolator from the box Fig 7/8
7

8

Next step is to pull off the purple wire from the spade/relay Fig 9/10
9

10

This purple wire can now be cut inside the box as it will not be used for the modification Fig 11/12
11

12

This can now be discarded or maybe keep it for future wiring ? i don't like to throw anything away Fig 13
13

Back to the control box the purple wire coming out the the control box can now also be cut Fig 14/15
14

15

That is the thick purple wire taken care of again set the wire to one side for use when ever, Fig 16
16

We now move onto the the thick brown wire which is connected to the relay with the grey wire, grip this with the pliers Fig 17
17

Then pull and remove from the relay Fig 18
18

Next we move to the thick black wire with the this trace wire attached to it, grip and remove this from the first relay Fig 19
19

Move the wire to the second relay and pop it onto there. Fig 20/21
20

21

Ok back to the thick brown wire we removed from that relay earlier, with the pliers cut this wire outside of the box Fig 22/23
22

23

That sorts out the thick brown wire from going into the box Fig 24
24

Cut the same wire from inside the box Fig 25/26
25

This will not be needed now so keep or throw it away Fig
26

The next step is to follow the thick brown wire attached to the large relay backwards Fig 27
27

Follow/trace this back up the loom to where it joins a split section Fig 28
28

You then cut this close to the joint Fig 29/30
29

30

The thick wire now attached to the joint is the one that you first cut from the control box earlier, this will later be spliced to the red wiring coming from the fan motor. Fig 31
31

This thick brown wire is also connected to the main wiring loom plug, which as the thin wires yellow, & blue /red wires attached too Fig 32
32

You /we now need to sort out the thick black wire in the control box with the thin black wire attached Fig 33
33


Follow / trace back along the loom until you find the split joint, Fig 34
34

Now cut the black wire that lead back to the fan motor leaving at least 8cm sticking out of the joint. Fig 35
35

Put that with the other wires you have cut from the control box & loom Fig 36
36

The control box is now ready to have the wire joined up to the loom, the thick brown wire from the large relay Fig 37/38
37

38

Will now have the end stripped back along with the thick black wire coming from the joint on the loom Fig 39
39

Join these together with a good glued based heat shrink connector, i also added some heat shrink to go over the that joint. Fig 40
40

The heat shrink glued connector Fig 41
41

Crimp and join these two wires together Fig 42
42

Seal the joint with a lighter Fig 43/44
43

44

I then slipped over the black heat shrink as a double protector Fig 45
45

Heat shrank that to seal. Fig 46/47
46

47

The thick brown wire in the control box as now become the thick black wire which would be in a control box with a two wire 2 speed fan,
it is marked it with some black all marker pen Fig 48/49
48

49

This then joins into the split connection and onto the thick black wire going to the plug. Fig 50
50

The other thick black wire coming from the split connection Fig 51/52
51

52

Enters the control box and is attached to the second small relay along with the grey wire. Fig 53
53

Now you need to add some heat shrink to the thick brown wire which was cut earlier at the split to seal the end off Fig 54/55
54

55

Make sure the joint is covered well and shrink tight Fig 56
56

The Grey wire in the control box, will be joined to the gold resistor Fig 57
57

The Red wire in the control box will be joined to black wire coming from the fan motor, which splits so the other end fits to the gold resistor also Fig58/59
58

59

Add some crimp connectors to each of the Red, Brown, & Grey wires Fig 60
60

Where the Grey & Red wire pass through the rubber control box joint, i have sliced through as sometimes you have to swap these wires over, Fig 61
61

Brown wire from the loom plug is joined to the Red wire coming from the van motor. Fig 62
62

The Red wire coming from the control box joins to the black wire from the fan motor & splits off to the gold resistor Fig 63/64
63

64

This is the set up after all the wiring and be changed over Fig 65.
65

Drawing of the above
66

Ready to fit to the car with the front of the cat still off hook it on the hangers, plug the fan into the loom of the car, make sure the A/C is in the off position, ignition to II no need to start the car, press demist and see if the fan runs in low speed if you think its running if high speed, then the Red & Grey wires in the control box need swapping over.

Another extensive guide. Thanks for that, Steve.

Jürgen wrote:Another extensive guide. Thanks for that, Steve.

HI Jürgen.
Thank you a member on the Nano needed to maybe use his diesel control box on a good petrol fan he has, hopefully this will help him, if not he knows where i am and can contact me other wise, little bit more to add if he needs it? if not i will maybe add it anyways.

It as took 14 hours over two days to post it up as the forum was only letting me add two photos a time after the first 30, and even they would only load occasionally contacted Mick whom seemed to think it may be Imgur but i posted them on the OC so i did not lose them on there they went over first try all 66 photos in about 10-12 seconds ?

I need to go through all my how to's on here as PB stole them when they purchased Tinypic, but at that rate i would be still doing them in 2025.