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please help me with engine fan


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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

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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.

when you are up to your armpits in alligators,

it is hard to remember you only came in to drain the swamp..

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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

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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

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on my 05 granite it is on the firewall, top passenger side. looks like this:

MAK20QE3373-500x500.JPG

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 by tjc transport

when you are up to your armpits in alligators,

it is hard to remember you only came in to drain the swamp..

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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?

when you are up to your armpits in alligators,

it is hard to remember you only came in to drain the swamp..

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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.

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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.

when you are up to your armpits in alligators,

it is hard to remember you only came in to drain the swamp..

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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.

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  • 2 weeks later...

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

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  • 1 month later...

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