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Dear Boxsterra

Both radiator fans on my 2008 Boxster s, 987.1 , do not work on low. Only high.

How do I jump this? using your hack?

Kind regards and thank you,

The fan control system on the 987 is completely different than on the 986 so my hack won't work. Also, the hack is to fix non-working high fan speed so it wouldn't apply in your case anyway.

The 987 fans aren't 2-speed (low and high) like on the 986 but instead are infinitely variable. They are supposed to turn on when the coolant temp is over 206° F and increase in speed until they are at their highest at 215° F.

On the 986 the fan low speed is controlled by ballast resistors and 4 relays (low/high, left/right).
On the 987 the fans are controlled by the front end control unit located at the right side of the front trunk (left side if you're facing the back of the car) under the carpet.

On the 987 the high amperage switching is controlled by a "cooling water blower control unit", located at the front right radiator. This is the replacement for the relays found on the 986.

If your coolant is above 206° F and neither of the fans is going on (make sure to double check by holding your hand under each radiator) but they are working at higher speed then I would suspect a problem with the coolant temperature sensor or the wiring from the temp sensor to the control unit. The easiest way to test the coolant temperature sensor is to connect an OBD-2 reader and read the temperature from there.

Edited 1 time(s). Last edit at 02/18/2023 09:44PM by Boxsterra. (view changes)

Thank you very much. I was certainly heading down the wrong road. I has almost ordered the wrong product.. Well I have some work ahead of me now. I don't have a lift so I best get the front bumper cover off and dig in.

Have a great weekend.

First steps
Boxsterra - 1 year ago
I wouldn't start by taking anything apart. I would start by verifying you fully understand the nature of the symptoms. Run the car until it gets up to over 206°, then put your hand under the bumper under the radiator on each side and see if you feel air moving. The solution may be very different if only one fan is failing versus both. Also the fan could be running but just very slowly.

If neither fan is running then use an OBD-2 reader to read the coolant temperature. If what you see isn't "realistic" then there is a problem with the sensor or the wiring to/from the sensor.

As an aside, OBD-2 readers are very cheap (I've gotten them for $5). If you're not in California, most auto parts stores will let you use theirs for free.
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