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Low Speed Fan Test

jcpr996
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jcpr996 Member

jcpr996

Posted
Posted

Hello Everyone:

How can you test the low speed of the radiator fans. With the A/C on both fans come on but want to check low speed.

TIA...

  • Moderators
RFM Member

RFM

Posted
  • Moderators
Posted

1) Let the engine idle with AC off after a run.

2) Remove the low speed relays and make a bridge with a wire, ignition on with cold or warm engine.

KevinMac Member

KevinMac

Posted
Posted (edited)

After car is warmed up AC off, leave it idle and take a strip of paper and put infront of the radiator, to see if there is airflow.

Edited by KevinMac
jcpr996 Member

jcpr996

Posted
  • Author
Posted (edited)

Well went to check this out after I got home, turned A/C off. I noticed the high speed fans, both of them start when the temp got to the far edge of the 0 at the temp gauge. Low speed didn't start at all at either fan. Will try the jumper at the relays. If you guys don't mind, what were the low speed relays, I know its been posted here before but don't remember. Just in case, it's a '99 tip cpe. so it has the third radiator.

TIA... :renntech:

Edited by jcpr996
1999Porsche911 Member

1999Porsche911

Posted
Posted
Well went to check this out after I got home, turned A/C off. I noticed the high speed fans, both of them start when the temp got to the far edge of the 0 at the temp gauge. Low speed didn't start at all at either fan. Will try the jumper at the relays. If you guys don't mind, what were the low speed relays, I know its been posted here before but don't remember. Just in case, it's a '99 tip cpe. so it has the third radiator.

TIA... :renntech:

The low speed relays are located in the driver's footwell and are slots 19 and 21. Ground pin #85 and the fan should run.

jcpr996 Member

jcpr996

Posted
  • Author
Posted

Ok got this tested the right way. Just removed one of the low speed relays then turned the a/c on and just one fan ran on low speed. A few seconds later then went to high speed and both ran. I guess I had never heard them on high speed, cause they are significantly louder and obviously they move more air. So all is good the noise I was hearing before was the fans on low. Thank you all for your help..

:renntech:

  • 2 months later...
zoomsan Member

zoomsan

Posted
Posted
Ok got this tested the right way. Just removed one of the low speed relays then turned the a/c on and just one fan ran on low speed. A few seconds later then went to high speed and both ran. I guess I had never heard them on high speed, cause they are significantly louder and obviously they move more air. So all is good the noise I was hearing before was the fans on low. Thank you all for your help..

:renntech:

Hi...so did you not try the jumpering suggested? All you did was take out 1 low speed relay and the car automatically kicked into high speed? Just curious if this is an easier way of seeing low/high speed fan flow differences. I guess a lot of people seem to confuse the low for the high.

perryinva Member

perryinva

Posted
Posted (edited)

No, it doesn't automatically choose high when low is not there. AC fans are on at low speed or when coolant hits a high temp. when coolant hits high-high temp, hi speed kicks in. If the OP's low speed fans didn't kick in before the high speed did, then he has a problem somewhere. Also, on my 2002, even if I let the car idle after a spirited run w/o AC on, even in the 90's, the low speed fans only turn on occasionally. I've NEVER seen (or heard) the high speed fans w/o jumpering the high speed relay contacts.

Edited by perryinva

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