E-Fan not coming on ? ?

1997 4.0
So my E-Fan is not coming on.
My Temps reached about 220 and it never came on.
What to check ?
Also can I hook up a seperate switch on the dash to manually turn it on, say when wheeling or setting in traffic on a hot day ?

Does it come on when the A/C is on? If no then check the relay and maxi fuse (distribution block). If it still doesn't work, hook up 12v to the plug with a jumper from the battery to check the fan motor.

If it does come on with the A/C, then it's probably the coolant temp. sensor.

jth877 said:

Does it come on when the A/C is on? If no then check the relay and maxi fuse (distribution block). If it still doesn't work, hook up 12v to the plug with a jumper from the battery to check the fan motor.

If it does come on with the A/C, then it's probably the coolant temp. sensor.

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Yes; comes on with A/C

Your 97 has the CTS in the thermostat housing and the PCM controls the efan based on its interpretation of the temperature.

My suggestion would be to install a manual override switch through a relay so you can run the efan on command.

An even slicker mod would be to install a second temperature switch/sensor in a heater hose, using a switch/sensor with a lower thermal threshold and a relay.

Diodes to isolate any potential feedback to the PCM would be a good safety measure.

Hylander said:

Yes; comes on with A/C

Click to expand...

Your gauge is probably off a little

The sensor in the thermostat housing provides the coolant temperature to the computer, which then does a bunch of stuff with that data, including turning on the fan at the threshold point and sending a signal to the gauge to show the current reading. Since the gauge displays temperature readings of some kind we know that the computer is getting temperature readings from the sensor (or else you'd have check engine light and the gauge would be dead). In addition, since the computer is able to turn on the fan when it detects the clutch circuit engaged then we also know that the fan control logic works. Ergo the computer has simply chosen not to turn the fan on, most likely because the temperature readings from the sensor are below the threshold value. This leaves the most likely explanation that the gauge is off, and is showing readings that are slightly above what the computer is getting from the sensor.

You can verify this by going to your favorite shop and asking them to plug up their engine scanner so that you can compare the gauge and computer temperature readings to each other.

Hylander said:

Also can I hook up a seperate switch on the dash to manually turn it on, say when wheeling or setting in traffic on a hot day ?

Click to expand...

Here's a write-up I did recently on how to manually control your radiator fan by tapping into the factory wiring. No need for a separate power circuit.

Radiator Fan Override Switch (The Easy Way)

You can check a couple of things.

-Disconnect your ect and see if you fan stays on all the time. This checks the pcm's circuit to the resistor.

-Hook up a scan tool and see what the actual temperature and or voltage reads from the sensor.

-Check the resistance of the ECT while comparing it to a chrysler chart and temp gun

-Or just do what joe said and hook up a relay so you can turn it on whenever you want

You can verify this by going to your favorite shop and asking them to plug up their engine scanner so that you can compare the gauge and computer temperature readings to each other.

Click to expand...

Did this and gauge is within 1 degree.
Also I just found out that my A/C is activated when I just turn the control switch to the vents for fresh air.
Also when A/c is on the E-fan still does not come on.
I had to unplug the A/C clutch to keep it from running.

Did you run a Hot jumper from the battery directly to the + side of the fan to check if the fan is OK?
Did you swap out the fan relay (Located underhood in the main electrical distribution panel) to check if it is OK?

Hylander said:

Also I just found out that my A/C is activated when I just turn the control switch to the vents for fresh air.
Also when A/c is on the E-fan still does not come on.
I had to unplug the A/C clutch to keep it from running.

Click to expand...

Sounds like a short in the HVAC head unit. That could make some knock-on problems with the fan control logic I suppose. The HVAC unit isn't hard to replace, just takes a while. Might want to get a junkyard or part-out donor and see if it fixes your problems.

In the meantime do the fan circuit tests described above, since the fan should be coming on whenever temperature gets up high or the A/C compressor clutch is engaged (regardless of error)

I'm having the same problem with my fan not coming on. Where is this relay and maxi fuse? How exactly can I jump a wire to test the fan motor by itself?

Ah. Mine comes on when I turn on the AC.

Its cured.
The Relay was melted.
New Relay and it works fine

sounds to me like you better plan on buying a new fan too.

The only reason the relay would melt is if the fan motor is drawing too much current.