Hey all,

so my 996 turbo engine coolant temperature hit 100c, and no front fans came on a - few times now, ie in traffic only. I understand they should come on to stage 1 at 100c.

plugged in Durametric and override got the fans on stage 1,2 an 3 no problem- so I guess fuses, relay and fans are all ok

A/C on - and stage 1 fans came on.

Leaves only the coolant sensor then ?? But the temperature is clearly displayed, so what is going on ?

Any help much appreciated

 

Did you use Durametric to see if there were fan stage errors? One time I had my Turbo in for a suspected bad fan -- it was running but not blowing the same volume of air as the other side -- the tech did this with the Porsche diagnostic computer and none were found but he then checked the fan current draw and found it higher than the other side which was working ok so I had him replace the suspected bad one.

For when the fans come on solely due to coolant temperature I've only really checked my Boxster's fans but they come on when the OBD2 code reader/data viewer displaying coolant temperature shows the coolant temperature at 212F. They are switched to high speed when the coolant temperature climbs to 216F. And they switch off when the coolant temperature drops to 205F.

However, there is no guarantee this 212F threshold is true for every model.

Maybe the temperature has to be over 100C? So maybe you need to redo this and get the temperature above 100C (212F)? Raise engine RPMs above hot idle RPMs. I wouldn't take it much above -- just a few degrees at most should be enough -- and if the fans do not come on I'd turn on the A/C -- or just use Durametric -- to turn on the fans to bring the coolant temperature down just to be safe.

 

I believe low speed (cooling 1) is run through a set of resistors that lower the voltage, many times these fail, and open circuit. If this is the case the relay will come on but low speed fan won't.