The ECT serves as the only input to the PCM for monitoring coolant temperature.
At the first trip point, the PCM energizes the low-speed fan relay located in the engine compartment fusebox. This relay applies power to the fan dropping resistor (located at the bottom driver's side of radiator shroud) and energizes the fan with a reduced voltage.
If the PCM sees the temperture hit the second trip point, it energizes the high speed fan relay with applies full power to the fan, bypassing the low speed circuit.
Interestingly enough, there is a test documented in the 95 service PCED in the PCM Quick Test procedure for the 95 that will test the LFC and HFC circuits., allowing you to toggle the high and low speed fans circuits on or off. If you have the service CD, it is in Section 5A.
The procedure, cut and pasted, is as follows:
Output State Diagnostic Test Mode (DTM)
The Output State DTM aids in servicing output actuators associated with the EEC system. It enables the technician to energize and de-energize most of the system output actuators on command. This DTM is entered after all DTCs have been received from Key On Engine Off and Continuous Testing. At this time, leave Self-Test activated and depress the throttle. Each time the throttle is depressed, the output actuators will change state from energized to de-energized or from de-energized to energized.
1. Enter Self-Test.
2. DTC Output Ends.
3. Do Brief WOT.
4. EEC Output To Actuators Energized.
5. Do Brief WOT.
6. EEC Output To Actuators De-Energized.
7. For vehicles with LFC and HFC circuits:
To cycle the LFC and HFC outputs after code output ends, depress and hold throttle. For LFC, wait until the MIL flashes once (10 seconds). For HFC, wait until MIL flashes twice (15 seconds). Release throttle. The LFC or HFC output is now on (to cycle output off, depress and release throttle).
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Hope this helps.
Steve
Steve
