I've been having trouble with a the fan clutch on a 01 KW t300. When the ac was turned on the fan wasn't coming on. I was told the fan wasn't turning on at all and the truck overheated. I put power and ground to the fan clutch solenoid and got nothing. I put in a new solenoid and it still wasn't working. Very rarely it would come on. I went looking for temp sensors to unplug. So looking for some verification at this point. I'm to believe that there's a switch on the ac low side that tells the fan to turn on. Then there's a temp sender for the gauge, and a temp switch for the computer and/or fan. On the top of the motor there's a block in line with the coolant lines that have two senders screwed in. Is it safe to assume that one is coolant level and the other is coolant temp to the gauge? One is a single stud in the center, and the other has a stud and a spade terminal. for the hell of it I unplugged both with the truck running to see if the fan would turn on. It did not. I went on a search for another temp sender. I found a switch on the passenger side of the block towards the front, kind of in the middle of the upper and lower coolant pipes. I unplug it and the blue fan light came on in the dash and the fan turned on. I figured that's my temp sender for the computer/fan control. I try to order it and the guy has no idea what i'm talking about. But I mean, what else would turn the fan on when unplugged? How are these things wired? If the temp switch is no good, would that affect the fan coming on when the ac is turned on? Hopefully someone here can educate me on these things! HELP!
I I don't remember exactly how these work but let me offer this: 1. I believe the fan clutch comes on when air is released so if it is staying off verify that it is because it is getting air pressure to the clutch and not because it is worn out. 2. I believe the electric solenoid is the same way, fails safe so if it has no power it should release air and the fan stays on. 3. A little fuzzy on this but I think the engine water temperature fan logic is a computer controlled parameter and it is usually in the range of 210-215 with small hysteresis but that was if it was a Cummins, or does yours have a Cat in it? 4. The A/C fan clutch logic is usually a switch located on the HIGH side somewhere near the receiver/dryer or on it, and if you unplug it you get the fan on for 2-4 minutes even if you plug it right back in. (The only other switch should be the low pressure cutoff which will be obvious because it will stop and start the compressor) Hope this helps.
I have an 06 t300 and the fan seams to come on at different parameters then other times. Never sure when it will come on
The solenoid was definitely no good.. I tried jumping power and ground to it and the leads got hot ha ha... I ohmed it out and it had very low resistance like, 1.x ohmes or something...One problem got solved with the solenoid, before the fan clutch light would come on the dash but the fan wasn't engaging. Now, it doesn't come on with the ac. Jumping or just unplugging the ac switch does nothing. It wasn't until I unplugged the temp switch... I'm guessing it was the temp switch, the fan came on immediately. But when I called to order it, they were clueless, tried giving me the ac switch, coolant level switch, the other temp sensor...everything but. This is a cummins motor. and ya know, I have another truck thats a few years different I could swap parts back and forth with. It's weird though, fan clutch wouldn't come on and the truck would overheat randomly. (Or so i'm told) I hooked up my little scanner to it and the temp matched the gauge so I figured it was all good. I think i'm just overlooking something. I think i'm going to take the ac right out of the equation and see the the fan clutch operates then.
I had to go to cummins directly for the sensor. Even they had it listed wrong. They were calling it a fuel temp sensor. It was definitely a coolant temp sensor. Either way, I replaced it and it made no difference. This past weekend I decided to dig in a little bit more. I had to change out the coolant lines from the air compressor to the block anyway, so I took this as an opportunity to check the wiring. I found 3 or 4 frayed and corroded wires going to the pcm. I ohmed out both the temp switch and the ac pressure switch, perfect. I lost track of how far the ac switch wiring went but They looked like they didn't go to the computer. This truck doesn't have a manual switch for the fan clutch, and I've found it difficult to find a wiring diagram that looks like what I have. Anyway, just getting my thoughts out on this.