How to test my 3 speed fan?

onlyslightlymad · 17th June 2012, 17:27

Had the front end off today to do a number of jobs, one of which was to re brush my 3 speed fan which wouldn't run on slow speed.

Long story short, after trying to get my aircon regassed the other day, the pressure went way to high to which the air con guy said that could be because the fan isn't running and cooling the condensor. Makes perfect sense to me, so he vacced it all out again.

Anyway, I fitted a new condensor today, re brushed the fan and tried to test things. Ignition on, demist selected and the fan did not run, so I guess the fan is still not working on low speed, and the re brushing job failed. That doesn't surprise me as when I opened up the motor there was only 2 1/2 brushes left, one had worn down to absolutely nothing. I guess it may have damaged to commutator or maybe the circuitry inside the motor.

My question is, how can I test the fan on the bench to prove if any of the 3 speeds are working?

I have tried shorting out the plug on the switch at the back of the engine as shown elsewhere on here and nothing happened. When I was on a run the other day, I was queueing in stop start traffic and as far as I could tell, it sounded like the fan came on on one of the higher speeds but I can't be positive on that as I didn't get out and look. I tried letting the car warm up on the drive after I put it all back together this afternoon, but it didn't get warm enough to kick the fan in on a higher speed, it only got to 60 whilst idleing.

Any thoughts?

onlyslightlymad · 19th June 2012, 08:53

Anybody got any ideas?

Unclefista · 19th June 2012, 09:25

If you have access to the control box, you can short the relays easy enough.

FrenchMike · 19th June 2012, 09:30

When you dismantled your motor ,what was the commutator state ?

Commut.jpg

If you have rebrushed as my 'how to',it must works.

Check fuses and relays ...

Mike

onlyslightlymad · 19th June 2012, 09:35

Quote:

Originally Posted by Unclefista

If you have access to the control box, you can short the relays easy enough.

Quote:

Originally Posted by FrenchMike

When you dismantled your motor ,what was the commutator state ?

Attachment 14750

If you have rebrushed as my 'how to',it must works.

Check fuses and relays ...

Mike

Good point, I don't know why I didn't think of that myself.

Now feeling slightly dumb as I am an electronics engineer by trade background and have been playing with cars for over 30 years!

martinhaven · 19th June 2012, 09:55

Also, would fan come on when using demist?

Sure way to check if it's working is to set temp to LO and hit the Auto button... should have immediate fan noise.

I don't. AGAIN.

Last time, wiggling the little dagger fuse 'cured' it. It didn't overheat for a few days but now the temp climbs in traffic...

Back under the bonnet I go...

SD1too · 19th June 2012, 10:27

Quote:

Originally Posted by onlyslightlymad

... after trying to get my aircon regassed the other day, the pressure went way to high ...

This happened to mine too. Was yours evacuated for half an hour?

Quote:

Ignition on, demist selected and the fan did not run, so I guess the fan is still not working on low speed, and the re brushing job failed.

Not necessarily. You could have a failed relay or, on your diesel, a PCB fault.

Quote:

... when I opened up the motor there was only 2 1/2 brushes left, one had worn down to absolutely nothing.

That's what normally happens to the 3 speed motor!

Quote:

My question is, how can I test the fan on the bench to prove if any of the 3 speeds are working?

Wiring colours to relay contacts:
Slow speed: +ve to red, -ve to black
Medium speed: as for slow speed plus +ve to grey
Fast speed: as for medium speed plus -ve to purple.
This will prove the motor, but you cannot test the PCB since it's input is a PWM waveform.

Quote:

Originally Posted by martinhaven

Also, would fan come on when using demist?

Yes Martin. It's the most reliable way of testing the low speed.

Quote:

Sure way to check if it's working is to set temp to LO and hit the Auto button...

Not always. If you experiment with this you'll find that sometimes the compressor and engine fan cut out as the interior temperature is reduced. It's a puzzle which hasn't been resolved yet.

Simon.

Arctic · 19th June 2012, 14:50

Hi will try and post up a video of a three speed later but for those whom have a silver resistor and are going to change it here you go
http://youtu.be/j3O5wDZSjUQ

http://youtu.be/RdGnDDWqRzw

Fitted to the car

http://youtu.be/uI2R2ILORLo

The video of the three speed four wire diesel fan with bushes this was testing before it was taken to the last nano meet for Mark3d to have the bushes replaced and fitted to his car Arctic.
http://youtu.be/lwSLzAj3u8g

onlyslightlymad · 19th June 2012, 18:46

Quote:

Originally Posted by SD1too

Wiring colours to relay contacts:
Slow speed: +ve to red, -ve to black
Medium speed: as for slow speed plus +ve to grey
Fast speed: as for medium speed plus -ve to purple.
This will prove the motor, but you cannot test the PCB since it's input is a PWM waveform.

That's what I need, thanks very much. Only problem is having to take it all apart again just to test it to then having to put it back together again so I can order what is needed and use the car to then take it all apart again to finally fix it! Still, I should be good at taking the front end apart by the time I have finished!

lovema75 · 19th June 2012, 18:52

My neighbourhood was amazed to watch the process of the front coming off!

17th June 2012, 17:27	#1
onlyslightlymad Retired Join Date: Mar 2012 Posts: 188 Thanks: 1 Thanked 5 Times in 5 Posts	How to test my 3 speed fan? Had the front end off today to do a number of jobs, one of which was to re brush my 3 speed fan which wouldn't run on slow speed. Long story short, after trying to get my aircon regassed the other day, the pressure went way to high to which the air con guy said that could be because the fan isn't running and cooling the condensor. Makes perfect sense to me, so he vacced it all out again. Anyway, I fitted a new condensor today, re brushed the fan and tried to test things. Ignition on, demist selected and the fan did not run, so I guess the fan is still not working on low speed, and the re brushing job failed. That doesn't surprise me as when I opened up the motor there was only 2 1/2 brushes left, one had worn down to absolutely nothing. I guess it may have damaged to commutator or maybe the circuitry inside the motor. My question is, how can I test the fan on the bench to prove if any of the 3 speeds are working? I have tried shorting out the plug on the switch at the back of the engine as shown elsewhere on here and nothing happened. When I was on a run the other day, I was queueing in stop start traffic and as far as I could tell, it sounded like the fan came on on one of the higher speeds but I can't be positive on that as I didn't get out and look. I tried letting the car warm up on the drive after I put it all back together this afternoon, but it didn't get warm enough to kick the fan in on a higher speed, it only got to 60 whilst idleing. Any thoughts?

19th June 2012, 09:25	#3
Unclefista Posted a thing or two Rover 75 CDT Join Date: Sep 2011 Location: Bradford Posts: 1,478 Thanks: 1 Thanked 14 Times in 8 Posts	If you have access to the control box, you can short the relays easy enough. __________________ Love is like a snowmobile, speeding across the frozen tundra. Which suddenly flips, pinning you underneath. At night the ice-weasels come... http://farm6.staticflickr.com/5331/6...77671f80_n.jpg

19th June 2012, 14:50	#8
Arctic Give to Learn Freelander 2 Join Date: Aug 2010 Location: West Midlands Posts: 18,829 Thanks: 1,155 Thanked 6,407 Times in 3,874 Posts	Hi will try and post up a video of a three speed later but for those whom have a silver resistor and are going to change it here you go http://youtu.be/j3O5wDZSjUQ http://youtu.be/RdGnDDWqRzw Fitted to the car http://youtu.be/uI2R2ILORLo The video of the three speed four wire diesel fan with bushes this was testing before it was taken to the last nano meet for Mark3d to have the bushes replaced and fitted to his car Arctic. http://youtu.be/lwSLzAj3u8g __________________ Arctic Givology Learn to Give Everything is Achievable ad altiora tendo. Check out our Nano meet dates http://www.midlandsnanomeets.co.uk/ http://www.the75andztclub.co.uk/index.php?thepage=howto " You do the work , we supply the expertise " Last edited by Arctic; 19th June 2012 at 18:58..

19th June 2012, 08:53	#2
onlyslightlymad Retired Join Date: Mar 2012 Posts: 188 Thanks: 1 Thanked 5 Times in 5 Posts	Anybody got any ideas?

19th June 2012, 09:30	#4
FrenchMike This is my second home Rover 75 Saloon Join Date: Aug 2007 Location: Avignon Posts: 4,466 Thanks: 94 Thanked 661 Times in 554 Posts	When you dismantled your motor ,what was the commutator state ? Commut.jpg If you have rebrushed as my 'how to',it must works. Check fuses and relays ... Mike

19th June 2012, 09:55	#6
martinhaven Newbie Rover 75 Join Date: Jul 2011 Location: Leamington Spa Posts: 13 Thanks: 0 Thanked 0 Times in 0 Posts	Also, would fan come on when using demist? Sure way to check if it's working is to set temp to LO and hit the Auto button... should have immediate fan noise. I don't. AGAIN. Last time, wiggling the little dagger fuse 'cured' it. It didn't overheat for a few days but now the temp climbs in traffic... Back under the bonnet I go...

19th June 2012, 18:52	#10
lovema75 This is my second home 75 Tourer CDT Join Date: Dec 2011 Location: Enfield Posts: 3,925 Thanks: 63 Thanked 431 Times in 237 Posts	My neighbourhood was amazed to watch the process of the front coming off!