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amcurrier · 08-17-2003, 09:28 PM

I have a 1994 Mustang with a 3.8L V6. The problem is that the fan never turns on and the car eventually overheats. Here's a rundown of the things I've already looked at:

1) The 60A Fan Fuse and the 10A Low Speed Monitor fuse are both ok, checked with multimeter.
2) The fan motor is ok, it runs when battery power is applied directly to the fan.
3) The Engine Coolant Temperature (ECT) sensor is ok, its low and high temperature resistance measurements are within spec.
4) The Constant Control Relay Module (CCRM) has power.
5) The voltage at the fan connector is always about 8.5V, regardless of engine temperature. This voltage seems to be generated by the Powertrain Control Module (PCM), measured at the 10A fuse.

The wiring on the '94 3.8L model is strange. Both the PCM and CCRM are wired directly to the fan motor power. The wiring diagram only shows a simple relay inside the CCRM controlled by the ECT as the driver for the fan motor power, although there is a power relay for the PCM inside also. Without knowing the particulars of each module, I can't tell which one is the point of failure.

Any suggestions on how I might further isolate the problem?

Thanks!

Aaron

08-17-2003, 09:28 PM	#1
amcurrier Registered Member Join Date: Aug 2003 Posts: 1	Engine fan never runs on '94 3.8L I have a 1994 Mustang with a 3.8L V6. The problem is that the fan never turns on and the car eventually overheats. Here's a rundown of the things I've already looked at: 1) The 60A Fan Fuse and the 10A Low Speed Monitor fuse are both ok, checked with multimeter. 2) The fan motor is ok, it runs when battery power is applied directly to the fan. 3) The Engine Coolant Temperature (ECT) sensor is ok, its low and high temperature resistance measurements are within spec. 4) The Constant Control Relay Module (CCRM) has power. 5) The voltage at the fan connector is always about 8.5V, regardless of engine temperature. This voltage seems to be generated by the Powertrain Control Module (PCM), measured at the 10A fuse. The wiring on the '94 3.8L model is strange. Both the PCM and CCRM are wired directly to the fan motor power. The wiring diagram only shows a simple relay inside the CCRM controlled by the ECT as the driver for the fan motor power, although there is a power relay for the PCM inside also. Without knowing the particulars of each module, I can't tell which one is the point of failure. Any suggestions on how I might further isolate the problem? Thanks! Aaron