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Radiator Fans Will Not Turn ON

Westland
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Westland Enthusiast

Westland

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2014 5.3l.  The truck will not overheat while driving which tells me the water pump and thermostat are functioning.  Temp sensor is sending because my gauge registers and my OBDII device reads comparatively.  Coolant level is correct.  The AC runs warm while at idle (compressor running and system properly charged).  At speed AC blows colder due to forced air over the condenser.  

 

I notice the driver side fan slowly spin up for only a few seconds before it then stops.  It then waits for a minute or two more before doing the same thing.  Both fan fuses (40A) are good.  12v at the fuses.  There is not a conventional fan relay located in the engine bay fuse box.  Nor is there one in the other two fuse panels.  All fuses on all boards are good. 

 

Obviously I'm at a loss.  I can't manage to directly test the fans due to the wonderful electrical plug design.  Some strange long white plastic stick in place next to the plug of which I cant see well to dislodge.  I find it hard to believe that suddenly both fans fail in unison. 

 

Does anyone have an idea of what may be causing this no-fan issue?

Westland Enthusiast

Westland

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I'm not ready to spend the $ for the hptuners scan tool.  I suspected a ground issue so I located the exact grounds per fan on the frame.  Each fan has its own ground location on either side of the front frame of the truck.  I cleaned those up but no joy.  I cleaned the ECM ground that is located on the left side of the engine down by the power steering pump.  No Joy. 

 

I was able to pull the connectors from the fans and each fan has 3 leads; Pin 1 - GND, Pin 2 - B+12v always on (from fuse), Pin 3 - not used/available, Pin 4 - Signal from ECM.  Hooked up jumpers to ground and applied 12v to Pin 2.  No spin on either.  I then added another jumper to Pin 4 and applied 12v to it at the same time.  No Spin.  So either I'm using too small of a gauge jumper wire set, not applying voltage correctly or the fans are both in fact bad.  Going to get some new fans coming while I keep thinking of ideas outside of that.  Still entertaining anyone with thoughts on it.  Will update.

swathdiver Senior Enthusiast

swathdiver

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The previous generation uses 3 relays to operate the fans.  Get a subscription to the shop manual at AllDataDIY so you can see how they are wired up and work.

 

Your AC probably needs refrigerant.

Westland Enthusiast

Westland

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I've been using alldata and its been amazing.  AC has been working fine but I went ahead and put my manifold gauge on it to see.  Checks out fine and the compressor turns on as well. 

 

Alldata showed me the fan wiring diagram and it would seem the relay/control is handled by the ECM.  1 Wire leaves the ECM and branches to both fans.  Each fan has a always hot 12v coming from the underhood fuse box.  Then of course the ground coming from the frame on each side.  Thank you for the idea though! 

Edited by Westland
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pokismoki Senior Enthusiast

pokismoki

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Posted (edited)

arent the new fans on these truck brushless, ? applying 12 volts wont turn them on good or bad.  check the shop manual might be the speed controller is smoked

Edited by pokismoki
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Westland Enthusiast

Westland

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Didn't cross my mind.  Yep, they are controlled with a PWM signal from a controller.  Good info, thank you!  I'm really missing the fan clutch right now. 

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pokismoki Senior Enthusiast

pokismoki

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only way i know to activate them manually is turning on AC, and dialing it to LO, then full blast on the blower, this will turn the fans about 30-40 %

 

i want to try poking around HPtuners, cause I think i can dial up the Duty cycle to 80% output with this method, handy for towing when i want to overide my 195 fan trigger point.

Edited by pokismoki
Westland Enthusiast

Westland

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Diagram showed the signal wire is accessible in a plug between the ECM and fans.  It is located next to the under-hood fuse block where the second battery tray sits.  It has 3 wires.  One is fan signal and the other two are for the ambient air temp sensor. 

 

I decided to take the harness out of the picture and jump ground/power (from battery) and signal directly to the left fan.  The fan repeated what it was doing from the beginning.  It bumps a couple times and then tries to spin up but stops after it almost reaches low speed.  That repeats after a minute or so.  The right fan does nothing when jumped the same way.  

 

So this should rule out the fan plugs/ harness/ grounds (all cleaned) and ECM signal.   Again I still find it hard to believe both fans failed together.  

 

It is possible that one fan fails and it makes no significant difference in engine temp.  Then later the second fails.  Local temps have been 90-95F. 

 

Engine temp sensor, AC pressure sensor both show to command the fans on/off.  Transmission fluid temp sensor might but I haven't seen it in any diagrams.  Still open to input. 

 

Engine has 170K miles btw.

Edited by Westland
pokismoki Senior Enthusiast

pokismoki

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Posted

relays shorting out for the fans?

i wonder if the tech2 clone tool can test and find the issues with the fan, otherwise take to dealer for a computer check up. 

 

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swathdiver Senior Enthusiast

swathdiver

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1 hour ago, pokismoki said:

i wonder if the tech2 clone tool can test and find the issues with the fan

 

Nope, it does not work on this generation.  MDI or MDI2 with GDS or GDS2 software will work, Snap-On Solus, etc.

Westland Enthusiast

Westland

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I put the new $600 fan assembly in the truck.  Cranked it up and cycled the AC.  Fans did not turn on.  Almost cried.  Then the fans turned on.  Almost cried again.  Problem solved on this one.  Thank you all for the input! 

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  • 5 months later...

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