75 CDT 3 speed to 2 speed help

n3m · 11th June 2011, 16:00

Hi All,

I know theres load around on fan changes but not sure if Ive done mine correctly.

Can somebody (Jules

) have a check of the following and let me know if this is ok?

Ive replace my old 3 speeder for a 2 speed fan but think ive mixed the wiring up somewhere.
The fan comes on with the air con which is great and i can also make the fan come on by shorting the trinery switch. But both tests result in the same fan speed!

Ive had to retain my 3 speed relay box as i was only supplied a fan with 2 wires and a resistor with a wire coming out each end.

Heres what Ive done...
Removed the Black wire from the high speed relay, insulated the removed connector and tucked out of the way leaving the thin black wire connected

Moved brown wire from the medium speed relay to the relay connector vacated by the black wire.

Disconnected the Grey wire.

Ive connected the red from the relay to one side of the resistor and the other side to the fan positive and the connected the purple to the fan positive - bypassing the resistor.

Does this sound right???

Thanks everyone.

T-Cut · 11th June 2011, 17:28

Your tests seem OK for a 2-speed system. If you disconnect the coolant temperature sensor, the high speed should run.

TC

n3m · 11th June 2011, 19:45

Thanks TC, mines a diesel does disconnecting the temp sensor apply?
actually shorting the trinery doesnt seem to work, thought it did this morning. maybe ive connected it up wrong and knackered a relay?!?

n3m · 11th June 2011, 22:03

has anybody else converted the 3 speed relay box to power the 2 speed fan?

Arctic · 11th June 2011, 23:04

Quote:

Originally Posted by n3m

has anybody else converted the 3 speed relay box to power the 2 speed fan?

Hi Ant
I am myself in the same process just brought a two speed fan with silver resistor which i found out today is no good, not working have ordered a new upgrade gold resistor from Jules, take a look at where i am so far i need to add today's results yet on testing the fan, Arctic.
http://www.the75andztclub.co.uk/foru...ad.php?t=86202

n3m · 12th June 2011, 10:18

Hi Arctic, I have read your post with great interest (brill pics btw) but as I think you have found the advice is difficult to follow!

Like you I have the fan, with two wires and a resistor with a wire coming from each end. What I dont have though is the 2 speed control box so I will have to rewire my 3 speed box to trigger 2 speeds.

All this swapping polarity and cutting wires is confusing me!!!

As I have retained my 3 speed controller I think I have got the switching side of the relays wrong. One mine Ive got relay black as ground (-) going to motor (-) and relay red (+) going to resistor and resistor going to motor (+). The purple high speed goes direct to motor (+). This is where I think Ive gone wrong.

If you retain your 3 speed controller maybe we can help each other out with our findings.

Its peeing it outside and I fear I'll have to take the fan off for the 4th time this week. I am getting pretty quick at it though

n3m · 12th June 2011, 15:33

Ok, Ive digested all the info I can and this is what I've come up with.
I havent tested them out yet as I would like to see what you all think is the correct/best option.
On the diagram Ive Illustrated it as a 3 speed fan with the option to join the wires together to create a 2 speeder with a resistor (following one of the guides on here). As I've got a 2 speed option I will just use the red and black.

So guys - A, B or C????

swinnie · 12th June 2011, 16:02

I would say c is correct one, The 2 speed is permament live and switched on negative. check post 8 and 12 from jules here http://www.the75andztclub.co.uk/foru...t=54943&page=2 .Derek

Jules · 12th June 2011, 23:32

The PWM fan PCB's differ also.
MGR/BMW in their wisdom not only changed the polarity, but also changed the order and function of the relays!

The 3 speed PCB
Large relay is for SLOW SPEED

Later 2 speed PCB
Small middle relay = LOW speed
Large relay = HIGH speed
Other small relay OUTPUT terminals NOT connected, but the coil windings are used. (I presume to fool the ECU that the later Fan is still a 3 speed)

If you use the wrong PCB, the HIGH speed will operate first.

Simple solution:
Swap Thick red and Thick Grey wires over in the control box

n3m · 13th June 2011, 07:25

Thanks Jules for your input - feel I pestered you a little into replying! Your input is greatly appreciated.

As my 75 is the old ('02) cdt diesel model and I have retained the original 3 speed relay box I'll give your idea of swapping the red and grey over in the relay box.

Quite excited to try it out - sad I know but I havent had a working fan in 5 years!!!

Thanks for you help, I'll post back the results. If the weather is ok after work I'll give it a go tonight.

11th June 2011, 16:00	#1
n3m Newbie Rover 75 CDT Con SE Join Date: Jul 2009 Location: MANCHESTER Posts: 12 Thanks: 0 Thanked 0 Times in 0 Posts	75 CDT 3 speed to 2 speed SOLVED! Hi All, I know theres load around on fan changes but not sure if Ive done mine correctly. Can somebody (Jules ) have a check of the following and let me know if this is ok? Ive replace my old 3 speeder for a 2 speed fan but think ive mixed the wiring up somewhere. The fan comes on with the air con which is great and i can also make the fan come on by shorting the trinery switch. But both tests result in the same fan speed! Ive had to retain my 3 speed relay box as i was only supplied a fan with 2 wires and a resistor with a wire coming out each end. Heres what Ive done... Removed the Black wire from the high speed relay, insulated the removed connector and tucked out of the way leaving the thin black wire connected Moved brown wire from the medium speed relay to the relay connector vacated by the black wire. Disconnected the Grey wire. Ive connected the red from the relay to one side of the resistor and the other side to the fan positive and the connected the purple to the fan positive - bypassing the resistor. Does this sound right??? Thanks everyone. Last edited by n3m; 14th June 2011 at 21:19.. Reason: fixed problem

12th June 2011, 23:32	#9
Jules This is my second home ZT 260 SE Twilight and 10 other 75 ZT's :O Join Date: Jan 2007 Location: Conwy NORTH WALES Posts: 11,094 Thanks: 512 Thanked 1,116 Times in 763 Posts	PWM PCB Fan control box The PWM fan PCB's differ also. MGR/BMW in their wisdom not only changed the polarity, but also changed the order and function of the relays! The 3 speed PCB Large relay is for SLOW SPEED Later 2 speed PCB Small middle relay = LOW speed Large relay = HIGH speed Other small relay OUTPUT terminals NOT connected, but the coil windings are used. (I presume to fool the ECU that the later Fan is still a 3 speed) If you use the wrong PCB, the HIGH speed will operate first. Simple solution: Swap Thick red and Thick Grey wires over in the control box __________________ [SIGPIC][/SIGPIC] Newbies do now!! 1. Plenum drains..all 3 or 4 year dependent 2. Cooling fan..All speeds functioning 3. Bonnet cable divider block

11th June 2011, 17:28	#2
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Your tests seem OK for a 2-speed system. If you disconnect the coolant temperature sensor, the high speed should run. TC

11th June 2011, 19:45	#3
n3m Newbie Rover 75 CDT Con SE Join Date: Jul 2009 Location: MANCHESTER Posts: 12 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks TC, mines a diesel does disconnecting the temp sensor apply? actually shorting the trinery doesnt seem to work, thought it did this morning. maybe ive connected it up wrong and knackered a relay?!?

11th June 2011, 22:03	#4
n3m Newbie Rover 75 CDT Con SE Join Date: Jul 2009 Location: MANCHESTER Posts: 12 Thanks: 0 Thanked 0 Times in 0 Posts	has anybody else converted the 3 speed relay box to power the 2 speed fan?

12th June 2011, 10:18	#6
n3m Newbie Rover 75 CDT Con SE Join Date: Jul 2009 Location: MANCHESTER Posts: 12 Thanks: 0 Thanked 0 Times in 0 Posts	Hi Arctic, I have read your post with great interest (brill pics btw) but as I think you have found the advice is difficult to follow! Like you I have the fan, with two wires and a resistor with a wire coming from each end. What I dont have though is the 2 speed control box so I will have to rewire my 3 speed box to trigger 2 speeds. All this swapping polarity and cutting wires is confusing me!!! As I have retained my 3 speed controller I think I have got the switching side of the relays wrong. One mine Ive got relay black as ground (-) going to motor (-) and relay red (+) going to resistor and resistor going to motor (+). The purple high speed goes direct to motor (+). This is where I think Ive gone wrong. If you retain your 3 speed controller maybe we can help each other out with our findings. Its peeing it outside and I fear I'll have to take the fan off for the 4th time this week. I am getting pretty quick at it though

12th June 2011, 16:02	#8
swinnie Avid contributor Alfa Romeo 156 2.4 JTD Veloce Join Date: Apr 2011 Location: gainsborough Posts: 161 Thanks: 0 Thanked 0 Times in 0 Posts	I would say c is correct one, The 2 speed is permament live and switched on negative. check post 8 and 12 from jules here http://www.the75andztclub.co.uk/foru...t=54943&page=2 .Derek

13th June 2011, 07:25	#10
n3m Newbie Rover 75 CDT Con SE Join Date: Jul 2009 Location: MANCHESTER Posts: 12 Thanks: 0 Thanked 0 Times in 0 Posts	Thanks Jules for your input - feel I pestered you a little into replying! Your input is greatly appreciated. As my 75 is the old ('02) cdt diesel model and I have retained the original 3 speed relay box I'll give your idea of swapping the red and grey over in the relay box. Quite excited to try it out - sad I know but I havent had a working fan in 5 years!!! Thanks for you help, I'll post back the results. If the weather is ok after work I'll give it a go tonight.