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Steve Tinker · 05-25-2013, 07:54 PM

Have a look at this which I got off the Renn Tech Forum for you, it may help ....

There are four relays in total. Two for the left fan, and two for the right. The first stage (or slow speed) relays - one for each side, are paralleled and will switch together, also the full speed relays are paralleled and will switch together too. They are switched directly from the DME, whether it decides the AC requires them or the engine is too hot.

The resistors being in circuit make the motors turn more slowly. If you're getting high speed but not low speed, the resistors are burned out"

A very easy way to test the resistors without having to dive under the car, is to remove relay 19 & 20. Measure the resistance between pin 5 (87) of socket 19 and pin 5 (87) of socket 20. This should be 0.55ohm. Remove relay 21 & 22 and repeat. Again, 0.55ohm.

After all that, the temperature sensor is a split NTC device that has one sensor for the instrument cluster and one for the DME. One can go bad without the other, hooking the car up to a diagnostic computer will show this straight away.

05-25-2013, 07:54 PM	#8
Steve Tinker Registered User Join Date: Dec 2008 Location: Queensland, Australia Posts: 1,522	Have a look at this which I got off the Renn Tech Forum for you, it may help .... There are four relays in total. Two for the left fan, and two for the right. The first stage (or slow speed) relays - one for each side, are paralleled and will switch together, also the full speed relays are paralleled and will switch together too. They are switched directly from the DME, whether it decides the AC requires them or the engine is too hot. The resistors being in circuit make the motors turn more slowly. If you're getting high speed but not low speed, the resistors are burned out" A very easy way to test the resistors without having to dive under the car, is to remove relay 19 & 20. Measure the resistance between pin 5 (87) of socket 19 and pin 5 (87) of socket 20. This should be 0.55ohm. Remove relay 21 & 22 and repeat. Again, 0.55ohm. After all that, the temperature sensor is a split NTC device that has one sensor for the instrument cluster and one for the DME. One can go bad without the other, hooking the car up to a diagnostic computer will show this straight away. __________________ 2001 Boxster S (triple black). Sleeping easier with LN Engineering/Flat 6 IMS upgrade, low temp thermostat & underspeed pulley. 2001 MV Agusta F4.