Rad Fans run with no key on cold engine

[wifes_truck]

Head scratcher .... with no key in ignition the dual fans will run. when key goes in and engine is turned over the fans stop running. Took the plastic engine cover off the intake to confirm where the clicking sound was coming from. had wife turn the truck key to on position and the fans would stop running and the click was coming from the (maf) area I am guessing. It is a large cylinder shape attached to the air inlet for the engine (wire plug coming out of it). ( I am a ford guy and it would be what i would call the maf clicking? Can take pic if needed). she turned the truck key to off and it would click again and the fans would turn back on.

from what I have been reading, I am about to change the Coolant sending unit. and will also check the relays while i am there. but if the fan is running there seems to be not a relay issue unless the relays control ground? I will also check for critters living in the plastic fuse box under area that i seen on a utube vid.

currently had to unplug the driver's side fan at the fan connection to stop the battery drain.

any other options please send my way.

the thing that has me questioning the relays is that the clicking sound that is coming from the (maf) area.

cheers thanks for your time and reading

2005 tahoe 5.3 aircon 4X4

 

[OR VietVet]

Welcome to the forum from Oregon.

Do the fans work normally when driving? I would expect a temp sensor or the relays, as you have started to point out.

 

[wifes_truck]

hi, from what wife says the truck has never over heated and seemed to be fine so i would guess all is ok. just started doing this today.

cheers thanks

 

[915_Tahoe]

Head scratcher .... with no key in ignition the dual fans will run. when key goes in and engine is turned over the fans stop running. Took the plastic engine cover off the intake to confirm where the clicking sound was coming from. had wife turn the truck key to on position and the fans would stop running and the click was coming from the (maf) area I am guessing. It is a large cylinder shape attached to the air inlet for the engine (wire plug coming out of it). ( I am a ford guy and it would be what i would call the maf clicking? Can take pic if needed). she turned the truck key to off and it would click again and the fans would turn back on.

from what I have been reading, I am about to change the Coolant sending unit. and will also check the relays while i am there. but if the fan is running there seems to be not a relay issue unless the relays control ground? I will also check for critters living in the plastic fuse box under area that i seen on a utube vid.

currently had to unplug the driver's side fan at the fan connection to stop the battery drain.

any other options please send my way.

the thing that has me questioning the relays is that the clicking sound that is coming from the (maf) area.

cheers thanks for your time and reading

2005 tahoe 5.3 aircon 4X4

The fan relays are controlled by ground signal, is this factory fan from GM or gm factory fans installed after the fact replacing the clutch fan.

 

[wifes_truck]

hi, thanks for the comment yes these are factory fans non clutch replaced. So if there is a short at relays this would confirm that they control a ground and the fans are live with no ground.

cheers thanks

 

[wifes_truck]

OK, I can do a couple updates. looked in the fuse box, cleaned out the old mouse bedding. sucked up with shop vac, old pine needles and shells. looked under the fuse wiring, all looked good no chewed wires. in the relay holder i opened it up and swapped the 2 relays that are the same and with no key in the ignition, plugged the fan back in. spun up instantly.

Did not replace the temp coolant sender, 1- don't know where to find it, 2- its getting cold on the bones and the turkey soup is hot. (BC canada here) so i will leave that for tomorrows project.

thanks for reading, and I was wrong on the MAF it is up at the intake where it clicks, a large unit right at the main air into the engine, has a plug with 6? wires into it.

cheers thanks

 

[OR VietVet]

When you find the coolant temp sensor, not the sender for the gauge, for the computer, unplug it and see if fans stop spinning.

 

[OR VietVet]

Look at these links. The video is for the sender and the first link is for the sensor. I believe it is that way unless I am wrong.

https://www.cashcarsbuyer.com/how-can-you-tell-if-your-engine-coolant-temperature-sensor-is-bad/

 

[wifes_truck]

Cheers Thanks, will do!

 

[wifes_truck]

ok, update....

Found the sending unit and un-plugged the wires. plugged in fan, instant spun up.

So i don't need to replace the sending unit and just place the new one on the shelf for when it does go.

This is telling me there has to be a grounding short somewhere in the system.

I need to know what the unit is that goes into the intake. Throttle body and air regulator?

If this is the troubled part why does it click when the power goes to it with the key on and off turning on the fans? what would ground out in there? I will also follow the wires from the relay box down to fans to see if a short is there. besides the relays, what is the procession of the wiring for the fans?

batt - fuse -temp sending (controller) - relay - fans

sequence .... power 12v live at fans - sending unit closes, sends ground to the relays - relays open/close and closes the ground to the fans?

cheers and thanks