Radiator upgrade confusion

azdesertrhino · Jun 23, 2005

After searching the forum regarding upgrading to a later model radiator, I'm a little confused.
First, I have a 90 XJ 4.0. I have a 94 XJ radiator from my wrecked Jeep, which does not have the port for the temperature sensor. In one of the posts I saw, it said something about the temp sensor is not just a switch to turn the aux fan on and off, but also ties into the ECM(?).
First question, what problems would I encounter if I just ran the aux fan all the time? I live in southern Arizona where it doesn't get very cold, and this time of year just stays hot.

Is the part about this not being just a swith correct? I don't want to jump across it and let the smoke out of something. :laugh3:

Thanks in advance,

8Mud · Jun 23, 2005

The simple solution is to take the two wires that run to the temp. switch in the old radiator and run them to a switch. If you touch the two wires together, it will close the relay and run the fan.
Madxj.com has a pretty good write up on raditor basics, that while not the same, as what you are doing. Gives the basics, that are the same, for a closed to open system conversion.
The temp. switch in the radiator has nothing to do with the ECM, the temp. sensor on the lower left of the block does and the one on the uper rear of the head, is a sender for the temp. gauge.
On the newer open system Jeeps there is a sensor in the thermostat housing, that turns on the fan, through the ECM.

Eagle · Jun 23, 2005

azdesertrhino said:
After searching the forum regarding upgrading to a later model radiator, I'm a little confused.
First, I have a 90 XJ 4.0. I have a 94 XJ radiator from my wrecked Jeep, which does not have the port for the temperature sensor. In one of the posts I saw, it said something about the temp sensor is not just a switch to turn the aux fan on and off, but also ties into the ECM(?).
First question, what problems would I encounter if I just ran the aux fan all the time? I live in southern Arizona where it doesn't get very cold, and this time of year just stays hot.

Is the part about this not being just a swith correct? I don't want to jump across it and let the smoke out of something. :laugh3:

Thanks in advance,

Mixed metaphor.

On your '90 it is just a switch.

On a '94, it is a sensor that feeds the ECU, and the ECU in turn controls the fan.

You can simply put 3M quick taps on the two wires going to your old radiator sensor/switch and run those wires to a SPST toggle switch in the cabin to control the fam manually.

azdesertrhino · Jun 23, 2005

Thanks for the input, wanted to make sure I didn't kill anything. :wave:

Thanks again,

Radiator upgrade confusion

azdesertrhino

NAXJA Forum User

8Mud

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Eagle

Lifetime NAXJA Member

azdesertrhino

NAXJA Forum User

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