bulldogmack42 Posted May 24, 2015 Share Posted May 24, 2015 I have 2 macks one is a cxu613 2007 model Vin# 018213 380 hp,it needs a ecm because the air fan is engaged all the time and the dealer said it was in the ecm, is there a way jump around ecm and make it work Quote Link to comment Share on other sites More sharing options...
gearhead204 Posted May 24, 2015 Share Posted May 24, 2015 with a little farm enginering i would think it could be done. the computer should be controling a solenoid which activates the fan, if you interupt the solenoid control curcit you should be able to install a kysor switch which would tell the fan when to kick on, if you have a/c you will also need to run the high pressure switch thru this curcit ( to keep from blowing up your a/c) i would also put a manual fan switch in the curcit as well Quote Link to comment Share on other sites More sharing options...
tjc transport Posted May 25, 2015 Share Posted May 25, 2015 look for the electric over air fan controller.2 wires go into it. one is 12 volts all the time, the other is a switched ground from the computer. jump the ground side to a good electrical ground and see if the fan clutch shuts off. if it does not, the problem is with the electric over air controller.if it does shut off, check the pressure in the high side of the air conditioning .if it is over 260-270 lbs, the fan clutch will stay locked up. high side pressure should only be between 150-200 lbs. Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment Share on other sites More sharing options...
bulldogmack42 Posted May 25, 2015 Author Share Posted May 25, 2015 technician plugged up another ecm that he just happened to have and the fan kicked off, he also told me that the head pressure was ok, I looked at the laptop and it showed a/c high pressure switch "on" and fan clutch "on", he also said he checked high pressure switch and it was good I don't know what to do to make it work it's killing my fuel mileage and power, if I could rig it to work temporarily then I can replace ecm later any ideas would be grateful Quote Link to comment Share on other sites More sharing options...
bulldogmack42 Posted May 25, 2015 Author Share Posted May 25, 2015 technician plugged up another ecm that he just happened to have and the fan kicked off, he also told me that the head pressure was ok, I looked at the laptop and it showed a/c high pressure switch "on" and fan clutch "on", he also said he checked high pressure switch and it was good I don't know what to do to make it work it's killing my fuel mileage and power, if I could rig it to work temporarily then I can replace ecm later any ideas would be grateful Quote Link to comment Share on other sites More sharing options...
bulldogmack42 Posted May 25, 2015 Author Share Posted May 25, 2015 The truck also has the fault indicator on the side of the engine and it was blinking 4 red lights which is an open circuit, after I reset it it blinks green now Quote Link to comment Share on other sites More sharing options...
bulldogmack42 Posted May 25, 2015 Author Share Posted May 25, 2015 Where is the electric over air fan controller located and what does it look like? Quote Link to comment Share on other sites More sharing options...
tjc transport Posted May 25, 2015 Share Posted May 25, 2015 (edited) on my 05 granite it is on the firewall, top passenger side. looks like this:my problem was an air leak. once we replaced the leaking 1/2 inch synflex line the fan started working properly again.for a temporary fix, i would add a ground wire to the air switch and run it into the cab to a toggle switch you can control. when you see the temp rise to 180 or 200º flip the switch to turn the fan on. once it cools off, turn the swich of. Edited May 25, 2015 by tjc transport Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment Share on other sites More sharing options...
bulldogmack42 Posted May 25, 2015 Author Share Posted May 25, 2015 Grounded electric over air solenoid and fan kicked out, for some reason the computer is not grounding that circuit to tell fan to disengage, does each circuit like the water temp have a independent ground? Quote Link to comment Share on other sites More sharing options...
tjc transport Posted May 25, 2015 Share Posted May 25, 2015 same thing the granite was doing.high AC high side pressure, bad coolant temp sensor, bad computer ground, and an air leak will cause the fan to stay on.does the air conditioner work? Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment Share on other sites More sharing options...
bulldogmack42 Posted May 26, 2015 Author Share Posted May 26, 2015 Yes a/c works fine, the technician said a/c head pressure and pressure switch was ok and correct me if I'm wrong but if it truly was high head pressure then Shouldn't that be eliminated by turning a/c off? When checking high pressure switch I did notice 12.33 volts on one wire with it unplugged and had continuity thru the switch itself but once plugged in only showed 0.12 volts thru it with key on does that seem normal? Even the wire that had 12.33 on it showed 0.12 after plugging it in, just seemed strange to me. Quote Link to comment Share on other sites More sharing options...
tjc transport Posted May 26, 2015 Share Posted May 26, 2015 if the AC is working, then it is not high pressure and you can rule out the air conditioning circuit. .whether the AC is turned on or off, if pressure is too high, the fan will stay on all the time.it could very well be a bad computer. i was just looking for other ways to pinpoint it. Quote when you are up to your armpits in alligators, it is hard to remember you only came in to drain the swamp.. Link to comment Share on other sites More sharing options...
milton350 Posted May 30, 2015 Share Posted May 30, 2015 Mine happened to be on all the time as well, solenoid was ok but computer wasnt sending signal to solenoid. Well what i did was i disconnected the fan solenoid wire + & - that feeds computer and bought me an on/off switch connected to + from battery then to + on solenoid and ground from solenoid to switch then to ground on chassis, now that way i can turn the fann off and on whenever i want but you have to be careful with engine temperature. If you re careful that will fix your problem and would be a 4.99$ easy fix instead of hundreds maybe thousands of dollars chasing the issue. Hope it helps you. Quote Link to comment Share on other sites More sharing options...
bulldogmack42 Posted June 13, 2015 Author Share Posted June 13, 2015 Well just to update on my fan issue, made another trip to same dealer and same tech for computer to possibly be reflashed and that didn't work but I had taken another ecm with me so we hooked it up and that also didn't work, fan ran all the time with either ecm and showed same thing on computer "a/c pressure switch on" " fan clutch on" and again wanted me to buy a new ecm which I declined I mean I just paid $600 for a diagnosis as it was, I came home confused and got to thinking that the chances of 2 ecm's having same issue couldn't be right and I knew the fan worked when the second ecm was on its original truck, I searched for small dealerships that had been in business for a long time and found one, I spoke with the service manager there and he was great he advised me of a issue with the wiring harness behind the oil filters and aLso guided me through removing that apad crap and how to just use regular pressure switches and after that I finally could hear air going into my fan hub which was leaking as well, I put a kit in it and now all is well, fan works as it should, I still think I have a little issue in my wiring harness but at least I know where to start with it, a big thanks to tucker truck down in eldorado arkansas and Mike the service manager there, if any of you have problems that you just can't figure out give them a try they are good people to deal with 1 Quote Link to comment Share on other sites More sharing options...
Dieselwrenches Posted August 2, 2015 Share Posted August 2, 2015 Just as a heads up. Intake air temp sensor reading wrong or faulting will cause fan to stay on all the time as well. That's an easy check. Quote Link to comment Share on other sites More sharing options...
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