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  • Fan Control Circuit High

    I’m coming up with Fault 647-03 which is the Fan Control circuit. I’m not using this circuit at the moment as I have another PWM controller. Am I missing something about this circuit? Is it actually required?

  • #2
    It might be looking for some resistance like it would see from a relay coil. Try hooking a relay up to it and see if it goes away.

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    • #3
      Odd, it hasn’t happened again. I finally got out and took it up to the gas station to fill it up with fuel for the first time. Probably 2 miles or so. Got a discharge fault, but that’s likely due to all the fans I’m running etc on what may be a marginal battery.

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      • #4
        The circuit is required. If you are not going to use it wire a resistor or easier a relay in to simulate the load.

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        • #5
          Odd, the manual does not state that it’s required. But clearly it is. Ultimately I discarded my PWM Derale controller and opted to use the Cummins circuit to control the fan. It’s working well now.

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          • #6
            That’s good. It seems to work well from the ecu.

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            • #7
              I'm having issues with my fans not coming on. I've only got 2.5V at the fan-high control wire from the ecu... Is it supposed to be this low? I got a fault code that my intake manifold temps were getting too high and would assume that the ecu would have engaged the fan relay but so far I get nothing. Any ideas?

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              • #8
                I still haven't seen my fan kick on. My temps just aren't very high. I've got to get into 4Lo and hill climb to get it up there normally (it certainly seems to vary a lot even in similar driving conditions). However I've heard of guys with similar setups that can't keep their engine cool. Of course we have had a mild summer. We're high humidity, but it's only barely been over 95F here this summer.

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                • #9
                  Hmm glad I'm not the only one. My radiator keeps the engine cool enough without a fan too I guess. I'm just surprised that high intake air temps wouldn't trigger the ECM to turn on the fan since one would assume most of us run the same fan for intercooler and radiator. Might reach out to Cummins on this one. I could wire in a switch but then I'd just be waiting around for that high intake temp fault code all the time or running the fan constantly sucking power out of the engine.

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                  • #10
                    What temps are you seeing?

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                    • #11
                      So yesterday I was reading 190F coolant with no fans running and the high intake air temp fault code came on. Today I decided to run it up a long grade to try to get the coolant temp up closer to the 225 limit and the fans kicked on finally, although I can't say exactly what temp they came on at. I got the temp up to 220 though when I pulled over to check and the fans were running. The temp dropped back down after that but the high intake air temp fault code is still active and the fans shut off so I'm happy that the ecu does turn on the fans eventually but it seems like the threshold should be lower.

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                      • #12
                        The fan hi and fan return signals will kick the fan relay on at 194F. If nothing is hooked to that circuit, the engine will trip a fault at 194 for fan driver circuit as it's looking for resistance. When Fred and I put together TubeSock on "Dirt Every Day" and took it out to film it on its maiden voyage, we were running a mechanical fan and ended up wiring a spare LED turn signal to that circuit just to keep the fault at bay and also so we could see when it was commanding fan.

                        The fan command turns back off around 183-187 (I believe) based on my personal vehicle. If you're seeing high charge temp fault before you're getting the coolant hot enough to trip the fan, it would indicate you may be a bit undersized on the charge cooler. You could remedy this by wiring an override on the fan circuit. I'm working with our tech team to verify whether or not we have the charge temp enabled to trigger fan in our calibration. Will report back!

                        EDIT-From the technical folks:
                        Coolant On - 90C (194F)........Coolant Off - 80C (176F)
                        Charge On - 85C (185F).......Charge Off - 80C (176F)


                        Last edited by Sanders; 10-07-2019, 01:58 PM.

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