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rvjimmy · 06-15-2015, 06:48 PM

I have a 2002 DS and the fan won't run on high speed. I'll try to make this short. I unplugged the accuator and it now runs on high. This makes me think it's the sensor. Anyone know which one it is and where it is. The MH was running 215 to 220 I stopped and the fan was only running slow so that's when I knew something was wrong. Any help would be appreciated. If not I will take it in and have them plug it in and see what's wrong.

Jim Oh by the way it's a 3126 CAT.

rvjimmy · 06-15-2015, 06:56 PM

I didn't know if I should post this here or on the CAT forum. I thought I would start here and then go to CAT forum.

Dutch Star Don · 06-16-2015, 11:17 AM

"rvjimmy".....I can't be much help, but typically when there is a failure the fan goes to high speed.....which it is probably designed to do with a total failure of the sensor. Your symptoms and test of the fan sound like a bad sensor.

I'm the type that if the sensor is reasonably priced, I would rather replace it myself than spend twice as much for a shop to diagnose and then replace it anyway. If it's not the issue, I look at it as preventative maintenance.

If you have a Freightliner shop near you, ask to see the part and you'll know what you;re looking for. It has to be close to the fan drive and will obviously have wiring leading to it from the fan.

Hopefully someone on here will post that has already replaced one.

DJJ · 06-16-2015, 02:47 PM

Is yours a side radiator with a Sauer Danfoss pump?

Jeff
2003 Dutch Star, 3126B Cat.

rvjimmy · 06-17-2015, 06:08 AM

Quote:

Originally Posted by DJJ

Is yours a side radiator with a Sauer Danfoss pump?

Jeff
2003 Dutch Star, 3126B Cat.

I believe that is what is has, as it says that on the accuator. And yes it is a side radiator. Jim

DJJ · 06-17-2015, 03:37 PM

On my side rad the Sauer Danfoss pump the control module has 3 wires. Black is ground, the red wire only has 12v when the ECM says the temp is under the set temp. So if you loose voltage for some reason the pump will go to high. The ECM cuts the voltage on the red wire when it want the fan to ramp up. The white wire has 12 volts all the time, if you turn the AC on the ECM sends a pulse signal down that wire to the fan control module telling it to go to high. So if you turn the AC on and the fan should go to high. The temp sensor on a 3126B is on the curb side of the motor, just above and to the right of the HEUI pump. Hopefully that's your problem as its the least expensive part.

Jeff
2003 Dutch Star, 3126B Cat.

Skip426 · 06-18-2015, 05:43 PM

Here's a diagram of sensor locations ; note for engines equipped with an air compressor and a hydraulic pump, the oil pressure sensor is re-located, and a " T " installed in it's place with feed lines to the air compressor and the remote oil pressure sensor.

rvjimmy · 06-21-2015, 06:01 AM

Quote:

Originally Posted by Skip426

Here's a diagram of sensor locations ; note for engines equipped with an air compressor and a hydraulic pump, the oil pressure sensor is re-located, and a " T " installed in it's place with feed lines to the air compressor and the remote oil pressure sensor.

Thanks for the diagram. Mine is a 330 but that makes no difference. I don't see one that says fan speed sensor, maybe it is controlled by the water temp sensor. Thanks again, I'll have to check it when I get home I'm at my family reunion camped out for now. Jim.