Radiator fans only run with a/c on

[Josephb0]

99 boxster. Originally my fans wouldn't run at all so I replaced both sides with a new motors and ballast resistors which let them run with the a/c turned on only. Just replaced all 4 relays for the high and low speeds but still nothing without my a/c. Any other ideas?

[maytag]

Originally Posted by Josephb0

99 boxster. Originally my fans wouldn't run at all so I replaced both sides with a new motors and ballast resistors which let them run with the a/c turned on only. Just replaced all 4 relays for the high and low speeds but still nothing without my a/c. Any other ideas?

What temperature are you expecting to see them come on at? I mean, you're not simply expecting them on all the time, right?

[2ata]

My fans very rarely turn on. IF they do, it's usually really hot weather and parked in traffic.

[blue62]

The Bentley book says that the ECU has to see:
206.2 degrees to trigger low speed fan operation
215.6 degrees to trigger high speed fan operation
or the A/C switched on
Hope that helps.

[Josephb0]

maybe i just didnt get my car hot enough for them to come on i thought they would have started around the 180 mark. Thanks!

[Josephb0]

thought i had read something that said they should start in low speed straight from startup but another comment said i need to get above 200f so ill try that next

[blue62]

Originally Posted by Josephb0

thought i had read something that said they should start in low speed straight from startup but another comment said i need to get above 200f so ill try that next

Nope
The ECU has to see 206+ before it triggers the fans at low speed.
If you have a OBDII scanner that shows engine coolant temp.
Hook it up and just let the car idle while you watch coolant temp.
When it reaches 206 the low speed should kick in.
Then you can compare your dash temp. gauge with what the ECU is seeing.
May give you a better idea of when your fans should kick in while driving and just seeing your dash temp gauge.