Secondary Coolant fan control

[1992B4C]

OK, so looking at the wiring daigram for the secondary fan, I see it is controlled by the ECM. This is consistent with the fact that when I put the ECM into diagnostic mode, both fans turn on, like they should. But then why do I have a temperature switch on the passenger side head? What does it do? I cannot find any diagrams for the 1990 vette referencing it.............. Here is the thread that started my questions (I am kevosiroc at thirdgen.org) http://www.thirdgen.org/techboard/di...r-i-think.html

[1992B4C]

Originally Posted by 1992B4C

But then why do I have a temperature switch on the passenger side head? What does it do? I cannot find any diagrams for the 1990 vette referencing it..............

OK, to answer my own question (and please correct me if I am wrong), that is the coolant temp sendor for the temp gauge.

[SunCr]

Passenger side head switch (actually a thermistor) controls the temp gage. Primary and Secondary Fan Relays are driven by the ECM based on signals from the Coolant Temp Sensor (below the Throttle Body on the Manifold) or the a/c signal from the Pressure Sensor on the high pressure line. Basically, reach a certain threshold from either and the ECM grounds the Fan Relays. Otherwise, ground the diagnostic link or set a troublecode and the ECM will ground the relays. If you want to troubleshoot, post the specific problems.