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

 

[OR VietVet]

The unit you unplugged, is it the one at the driver's side front under or near exhaust manifold? If that is the case, that one will not make the difference. That is the SENDER for the gauge. The sensor for the computer is in the other location that I sent the link for. On the intake on front area on passenger side of throttle body. When you take the air pipe off you should be able to access and unplug there and when key is on it may set a code for that.

 

[wifes_truck]

ahhhh ok cheers yes that was the one i un-hooked. i will check the other one.

on another note I found this... will be looking at this also. cheers will up date.

""
Problem fixed. There is a box just under the battery next to the radiator. It has two plugs with an extreme amount of wires held in place with a 6mm bolt. I pulled and to my surprise the plug in was wet and the bottom few male pins were corroded pretty bad. The male side has a blue cover over the pins. I removed the cover to have better access to cleaning the pins. Once uncovered ,the bottom pin looked to have some kind of growth that may have been touching the metal casing and possibly causing a short. Cleaned well with contact cleaner small wire brush contact dryer and then electric grease. Note: the gasket goes on the male plug side.""


Read more at: https://www.obd-codes.com/forums/viewtopic.php?t=15461
Copyright OBD-Codes.com

 

[Joseph Garcia]

Somebody here can get you a picture of the wiring diagram, or can tell you where you can go to find one.

 

[OR VietVet]

That sounds like may be the problem. That corrosion comes from battery leakage. Poor place to mount that anyway. If is the problem and you clean and fix it, I would figure out a way to cover and protect it. If you unbolt and clean, I would unplug all and check for corrosion inside the pins and connector housing.

 

[OR VietVet]

Somebody here can get you a picture of the wiring diagram, or can tell you where you can go to find one.

That is why I like ALLDATAdiy.com but I know there are other free sources for the wiring diagrams.

 

[wifes_truck]

OK... I figured out the problem....

1- stuck a trouble light into the pos end of the fan plug and grounded other end. no key light on. (easier to use than having fans blowing)

2- opened up the relays again to double check. top (alone relay) controlled the light, unplug plug it in. light went on off.... other relays did nothing.key on off no difference except the light stayed off.

3- decided to next try the ^^^ above idea.... took off neg bat cable and took off the PCM cover....

4- started to unscrew the first bolt to the point that the harness was loosened off. jiggled and wiggled it, then screwed the bolt back in to tight and wanted to see if that made any differences.... secured neg cable back into batt

5- Test light stayed off .... plugged into the fan .... no running fan

The wires going into the PCM? at the connections were loose or needing a jiggle.

I didn't completely take the plug out.

Problem solved

Thank you all for your support. I am sure there will be new problems arise as she loves her truck and I doubt think she is getting rid of it anytime soon. As she bought it 2 years ago after a hard search for it. first major problem that we have encountered.

cheers all ...

 

[OR VietVet]

Glad it got taken care of and for close to no cost. I would still get in there and inspect all connections for corrosion and tight and clean and even get a cover on it, but your call.

 

[wifes_truck]

there is the big PCM box cover on it, (pain in ass to remove) the whole connection plug seemed so neat and dry that I just figured why open a can of worms by fully opening it up. By wiggling the plug in and out a few times seemed to clean the connections enough to re-seat the pins.

If it happens again I know what to do to fix it.

Just a strange thing to happen and was wondering how common this problem is. First I have heard of it.

cheers and thanks for the help.

 

[OR VietVet]

Do you live in an area where they use salt on the roads?

 

[wifes_truck]

Vancouver bc area, they brine the roads with "god knows what" some watery mix of ??? could be a salted mix. the whole area seemed so nice and clean and dry that is why I didn't fully pull the plugs apart. And I guess the wiggling was just the right amount of play to "clean" the connections. as i said will keep an eye on it.