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IanG1
Trainee


Joined: 08 Jan 2016
Posts: 96



PostPosted: Mon May 07, 2018 6:29 pm    Post subject: Radiator fans, quick question Reply with quote

Quick one, when I turn on my aircon neither of my fans run at slow speed? Is most likely problem the resistors, checked the fuse and OK. Need to pull the car out to check the relay.
 
  
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deMort
Zolder


Joined: 21 Mar 2015
Posts: 5018
Location: Brighton


PostPosted: Mon May 07, 2018 6:32 pm    Post subject: Reply with quote

You need to give it a min or so .. if neither work then the fan resistors are the most common failure .

Both fans run seperate relays for low and high speed .. for it to be the relays then x2 have failed .. a little unusual shall we say .
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skinny_monkey
Nürburgring


Joined: 16 Sep 2014
Posts: 376



PostPosted: Mon May 07, 2018 7:24 pm    Post subject: Reply with quote

both of my resistors had gone. But who knows how long the previous owner had left it with one gone. They also had a left it with a leak in the aircon so it wouldn't turn on and operate the fans anyway.
Replaced the a/c pipe with the hole, got it re- oiled / gassed and both resistors replaced (with genuine). 3 years on and all still spot on
 
  
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deMort
Zolder


Joined: 21 Mar 2015
Posts: 5018
Location: Brighton


PostPosted: Mon May 07, 2018 7:35 pm    Post subject: Reply with quote

Ive just done a write up of how to check them after reading this post ..

http://911uk.com/viewtopic.php?t=127681
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IanG1
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Joined: 08 Jan 2016
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PostPosted: Tue May 08, 2018 6:03 pm    Post subject: Reply with quote

Cheers guys, very helpful thanks

Ian
 
  
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DavidM
Newbie


Joined: 22 Oct 2017
Posts: 17



PostPosted: Tue May 15, 2018 6:58 pm    Post subject: Reply with quote

Am I right in thinking you could join terminals 85 of the low speed and high speed relay holders to effectively run the high speed fan at the lower temp without the need for a ballast resistor?
Thanks
 
  
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DavidM
Newbie


Joined: 22 Oct 2017
Posts: 17



PostPosted: Tue May 15, 2018 7:11 pm    Post subject: Reply with quote

Also if doing this would you need to cut the low speed/temp feed to the ballast resistor to avoid two power feeds going to the fan?

Would like to simplify the system and if it can run the fans at high speed only so cooling quicker without the need for ballast resistors then surely that’s a good thing?
 
  
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deMort
Zolder


Joined: 21 Mar 2015
Posts: 5018
Location: Brighton


PostPosted: Tue May 15, 2018 7:43 pm    Post subject: Reply with quote

You could .. but when you turn on the A/C the fans would run at full speed .. in fact when ever the low speed cut in it would run at full speed .. you would end up with over cooling .. more so with A/C turned on as it runs continually.

Bear in mind there is a temp operateing range for optimum efficency of an engine .. this way and it would be too cold ... also not sure how long the fans would last if run all the time at full pelt .
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skinny_monkey
Nürburgring


Joined: 16 Sep 2014
Posts: 376



PostPosted: Wed May 16, 2018 8:53 am    Post subject: Reply with quote

It wouldn't be as efficient to run with fans at full pelt all the time but I wouldn't be worried about overcooling - at 70 mph you're putting a lot more air through the rads than the fans will. Plus if you do start to overcool, the thermostat will just start to close and reduce the water flow through the rads.
 
  
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DavidM
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Joined: 22 Oct 2017
Posts: 17



PostPosted: Thu May 17, 2018 8:14 pm    Post subject: Reply with quote

Yeah I’m confident overcooling would not be an issue, fans maybe slightly loud in slow moving or stationary traffic with a/c running. I’ll prob stick with the standard setup for now but good to know it can be done. Thanks for the replies.
 
  
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