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pietrzj
Spa-Francorchamps


Joined: 19 Mar 2014
Posts: 266



PostPosted: Sat Apr 27, 2019 7:41 pm    Post subject: Fan Belt warning switch - Fixed Reply with quote

All,

I had the warning light come on recently. Not on all the time, just occasionally and more frequently this last week. I changed the belt a year or two ago and visually it was fine, but looked fine when I checked it this week other than a bit slacker than 5mm so I took a shim out. No change the the warning light so I dug deeper.

The switch itself is not a sealed unit and is only held on with one alan stud, so was easy to remove and strip down.

It was then obvious that it could not have been triggering due to a slack belt as the cam travel of the switch really only activates over large distances i.e when the belt has snapped.

I tested the resistance across the two pins and found it was not a clean closed circuit. The resistance was varying from 10s of ohms to 0.1 ohm. So the fault was within the microswitch itself.

I carefully removed the microswitch and cable assembly by scraping to top of the two plastic pins and sliding it up and out.

I then cleaned the whole unit up and, using contact cleaner, soaked the switch such that the tiny pin actuator was submersed as I operated it manually to ensure the contact cleaner got right inside.

I left it submersed in the cleaner (using the lid as a container), over night and dried it off in the morning. The resistance was now a solid change between 0.1ohm and infinity when operating the switch - Fixed!!!

Reassembly was straight forward and for good measure I greased up the bearings in the plastic wheel.

The saved me £77 + VAT for a replacement part, so well chuffed.

Really easy fix, so if you get something similar and its not a missing fan belt. Give it a go.

Hopefully the photos will help...
 



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pietrzj
Spa-Francorchamps


Joined: 19 Mar 2014
Posts: 266



PostPosted: Sat Apr 27, 2019 7:42 pm    Post subject: Reply with quote

Microswitch
 



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pietrzj
Spa-Francorchamps


Joined: 19 Mar 2014
Posts: 266



PostPosted: Sat Apr 27, 2019 7:42 pm    Post subject: Reply with quote

contact cleaner
 



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pietrzj
Spa-Francorchamps


Joined: 19 Mar 2014
Posts: 266



PostPosted: Sat Apr 27, 2019 7:43 pm    Post subject: Reply with quote

microwitch cleaned
 



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pietrzj
Spa-Francorchamps


Joined: 19 Mar 2014
Posts: 266



PostPosted: Sat Apr 27, 2019 7:47 pm    Post subject: Reply with quote

microswitch re-fitted
 



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pietrzj
Spa-Francorchamps


Joined: 19 Mar 2014
Posts: 266



PostPosted: Sat Apr 27, 2019 7:49 pm    Post subject: Reply with quote

re-assembled
 



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pietrzj
Spa-Francorchamps


Joined: 19 Mar 2014
Posts: 266



PostPosted: Sat Apr 27, 2019 7:49 pm    Post subject: Reply with quote

rear
 



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pietrzj
Spa-Francorchamps


Joined: 19 Mar 2014
Posts: 266



PostPosted: Sat Apr 27, 2019 7:50 pm    Post subject: Reply with quote

contacts to test
 



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pietrzj
Spa-Francorchamps


Joined: 19 Mar 2014
Posts: 266



PostPosted: Sat Apr 27, 2019 7:51 pm    Post subject: Reply with quote

Refitted - Job Done.
 



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Cameltoe & Heel
Barcelona


Joined: 26 Jan 2009
Posts: 1327
Location: Preston - Lancs


PostPosted: Sun Apr 28, 2019 7:38 pm    Post subject: Reply with quote

Love these posts, well done sorting it out. I did a similar thing with mine, although I had to lube the wheel up as it was getting s bit sticky.

Trev
 
  
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Luddite
Spa-Francorchamps


Joined: 18 Dec 2018
Posts: 337
Location: Scotland


PostPosted: Sun Apr 28, 2019 8:15 pm    Post subject: Reply with quote

Great job peitrzj you have covered the whole task very well, good pics too .... when the switch is in position on the car correctly adjusted, are the contacts opened or closed....?
 
  
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alex-j
Trainee


Joined: 30 Nov 2009
Posts: 53
Location: Sheffield


PostPosted: Mon Apr 29, 2019 11:25 am    Post subject: Reply with quote

Nice work Thumb
 
  
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pietrzj
Spa-Francorchamps


Joined: 19 Mar 2014
Posts: 266



PostPosted: Tue Apr 30, 2019 6:49 pm    Post subject: Reply with quote

Luddite, its closed circuit for normal operation and open circuit when the belt fails.

Jan
 
  
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9xxnick
Monza


Joined: 29 Jul 2014
Posts: 184



PostPosted: Thu May 02, 2019 8:05 am    Post subject: Reply with quote

I wonder if there's any mileage in getting the wheel that rests against the belt remanufactured as a spare. That's the bit that normally fails.

A slight redesign so that the full width of the wheel rests on the belt wouldn't be a bad idea either.
 
  
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Luddite
Spa-Francorchamps


Joined: 18 Dec 2018
Posts: 337
Location: Scotland


PostPosted: Thu May 02, 2019 11:35 am    Post subject: Reply with quote

Jan... Many thanks for taking the time to reply to that which some might think was my seemingly stupid question... (-: Just that logic determines in old fashioned wiring that switch would be configured as a "fail safe" device with a N.O. switch (Normaly Open contacts), the contacts then becoming CLOSED when the wheel is in contact with the belt....the thinking being that if either the switch, the wiring or any connection in the circuit failed at any time... the alarm would be raised.

N.O. or N.C. (normally closed) relates to the switch contact arrangement with the switch at rest.. i.e. in this particular case NOT physically in contact with the belt during testing.

The issue for me was that these days it is possible though perhaps less than "good practice" for digital programming as used in almost everything electrically related, to use either N.O. or N.C. switch contacts to crate some form of positive action like bringing ON an some sort of indicator.

Jan...I guess like others here you may be well aware of all that I have typed and sincere apologies if I come across as pedantic, I am not, though my contribution is hoped to help if someone unsure of electrics beams up your super work on solving the issue...and may be left seeking a little more understanding... Question

Thanks again.
 
  
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pietrzj
Spa-Francorchamps


Joined: 19 Mar 2014
Posts: 266



PostPosted: Mon May 06, 2019 8:56 pm    Post subject: Reply with quote

Luddite - its a N.O switch to use your nomenclature. Sorry, I dumbed down my last post - that will teach me.
 
  
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Luddite
Spa-Francorchamps


Joined: 18 Dec 2018
Posts: 337
Location: Scotland


PostPosted: Mon May 06, 2019 11:15 pm    Post subject: Reply with quote

pietrzj, nothing dumb about your well thought out contribution, thanks for taking time to reply.

Old style micro switches can have three terminals and use the I.D. N.O. N.C. and COM Com being short for Common which identifies the terminal which connects to either the N.O. or N.C. dependant on the position of the switch action. I mention this in the off chance that an alternative switch may be used in the assembly should that be all that is available at some future time by someone reading your post..
 
  
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