FEOA Forums banner
1 - 1 of 1 Posts

107 Posts
a bad sensor shouldn't cause the fuse to keep blowing, as the sensor isn't even in the power loop for the fan.

check for sticking relays in the CCRM, and then check BOTH sides of the cooling fan for a short.

According to the wiring diagram in My haynes manual, there are two sets of windings in the fan motor (fan has a three pin plug, yes?) the black lead to the fan will be the chassis ground, and green/yellow lead and the yellow lead are controlled by two separate relays in the CCRM. (LFC & HFC::lowspeed fan control/highspeed fan control)

check the ground connection for the fan, VISUALLY, to make sure that all connections are tight and clean. Also check inside the connector for corrosion (you DO apply an anti-corosive lubricant to the connectors, don't you?)

Also check the ground lead at the CCRM (black or black/yellow).

loose ground connections will cause high current draws.

when you tested the fan with battery, did you use an ammeter or a fuse in the test circuit? A shorted winding may allow the fan to operate, but draw excessive current.

Disconnect the coolant temp sensor, turn the key to run, and see if the fan kicks in. (the one on the RIGHT/rearmost,normally, when viewed from the driver side of the car) Also, make sure that there is a GOOD ground (ie, 0 ohms resistance) between the metal case of the sending unit and chassis/engine ground.

as a second order diagnostic: do you have a second CCRM that you can swap in? A sticking relay in there MIGHT cause both side of the two speed fan control circuit to be hot at the same time, which could also lead to excessive current draw.

As a third order diagnostic: two test lights, connected to the CCRM between the green/yellow wire and ground, and the yellow wire and ground, respectively, will tell you if the CCRM is trying to turn the fan on. (green/yellow for lowspeed, and yellow for highspeed) If a light turns on, but the fan doesn't. Check the fan again. Both windings.

From the circuit diagrams and your description, three things are suspect:

Engine Coolant Temperature sensor
CCRM (possible sticking relay or failed solid state relay)
Cooling Fan (possible hot-short winding)

A multimeter, a couple of test lights, and a heavy duty ammeter (or a handful of fuses) are all you should really need to do these diagnostics.

With the fan not running unless the AC is on, I'd suspect either the ECT or CCRM, but a faulty winding in the fan MUST be ruled out as well. And, of course, check all accessible wiring for damage that might cause an intermittent short.
1 - 1 of 1 Posts