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Low Speed Fan Test

jcpr996
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RFM Member

RFM

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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.

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jcpr996 Member

jcpr996

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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
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1999Porsche911 Member

1999Porsche911

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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.

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jcpr996 Member

jcpr996

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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:

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  • 2 months later...
zoomsan Member

zoomsan

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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.

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perryinva Member

perryinva

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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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