RADIATOR FANS STAY ON

obregon32 · October 29, 2019

I drive a 2014 Silverado 1500LT 5.3L V8

I noticed my radiator fans stayed on during my 20min drive to work, the ac was not on. temperature gauge did not move from 160*. After i parked and turned the truck of the fans still stayed on. So i started it back on for 20 sec. turned it off and the fans turned off. Another thing, i turned my ac to cold, but for some reason it doesn't get cold while the temp is at 160* and the fans are running non stop. I got home didn't mess with it, the next day everything was fine, ac was blowing cold, temp gauge actually read the temperature. the fans did not stay on. i get off from work and it starts doing the same thing. My brother said it might be a relay, i googled info on this and asked people and many said its probably a relay. i went to the auto-parts store told them what the issue was, and they sold me an ac control relay, which is #68 on the relay diagram on the fuse box. Has this happen to anyone else? my truck is no longer under warranty and i'm not trying to pay a lot of money to a mechanic unless i have to. any advise is greatly appreciated. Thanks.

Fyi i did a check engine light check at advance auto parts, they did a reset on my truck, i got home disconnected the battery and changed out the ac control relay. im waiting to see if it starts acting up again hopefully not.

1SLOW1500 · October 29, 2019

The fans are a two stage progressive control. And have input triggers of many things. Like ac, trans, ambient temp, engine temp, ect....
So first is to look at all temps. Oil, coolant, and trans. Then see what fan is spinning, 1 or 2. And how fast. Are they same speed. Last you can run a scanner and see the fan and speed. But without looking I remember 160 the fan starts to move but isn't till higher temp it speeds up. But again if ac is not charged or hasn't been run in long time that can cause it to trigger. Did on my truck, after a recharge and running it on full blast to mix the new coolant fans speed dropped.

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flyingfool · October 29, 2019

thermostat is bad, it stuck open, i only had this happen twice , when i used a low quality t-stat, , for some reason if the engine doesnt warm up it turns the fans on . this is why i love my old sierra , no electric fans just mechanical set up. very simple

Edited October 29, 2019 by flyingfool

ksiesel · October 29, 2019

12 minutes ago, flyingfool said:

thermostat is bad, it stuck open, i only had this happen twice , when i used a low quality t-stat, , for some reason if the engine doesnt warm up it turns the fans on . this is why i love my old sierra , no electric fans just mechanical set up. very simple

Could the reason for turning the fans on when the coolant temp doesn't come up be a fail safe for a failed in range coolant temp sensor? By turning the fans on, you prevent engine overheat in this scenario.

Back in the days of a belt driven mechanical fan clutch, this wasn't needed as the fan clutch was reacting to the heat coming off the rad and they were designed to fail full on.

truckguy82 · October 29, 2019

I one timed cleaned my maf with maf cleaner.

All i did was unplug it, Took it out, spray it down, and put it back in. About an hour later I drove it. Obviously all the maf cleaner had long since evaporated.

My radiator fans were running full tilt for like 10 minutes, just because I unplugged my MAF and plugged it back in, while the truck was completely off.

Cliff notes, they certainly have some odd programming for those fans. There is zero reason for them to run full tilt in the winter when the motor is cold, just because I unplugged the maf when the truck was completely off. Good luck

flyingfool · October 29, 2019

i believe it is a failsafe for a dead sensor

obregon32 · October 29, 2019

@1SLOW1500 temp doesn't change from 160* while the fans stay running its stays there. While this is happening the ac does not cool at all. Like i said the computer got a reset yesterday and right now everything is working normal. I'm pretty sure it'll start doing it again!

obregon32 · October 29, 2019

@flyingfool

so will this cause the fans to run all the time, they run at fool speed and its really loud.

1SLOW1500 · October 29, 2019

i believe it is a failsafe for a dead sensor

Very possible. That would.be a trigger. My ac need recharge and had pressure but caused the fans on full every time I requested ac. Relay fail rate is like 1 in a 100million. But still.possible

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flyingfool · October 29, 2019

6 hours ago, obregon32 said:

@flyingfool

so will this cause the fans to run all the time, they run at fool speed and its really loud.

yes

obregon32 · October 31, 2019

i disconnected the battery then switched out the ac control relay, after advance auto reset my computer. The issue with running fans is gone now they are working properly. Im taking it today for another scan since the check engine light came on again. Next Question.

What psi should my oil pressure be at? While the truck is running, parked, and during acceleration? Im asking because right now its a little bit passed the 40psi and when i accelerate it shoots up to almost 45/50 psi. is this normal?

im almost due for an oil change, my truck has 117000 miles.

1SLOW1500 · October 31, 2019

2 stage oul pump and when warm you can see much lower pressure so you are good.

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Wooderd · September 17, 2020

My 2015 Silverado 6.2L Z71 Off Road LTZ just started with the fans running all the time when driving. The engine temp is good at 260, the fans shut off 5-10 seconds after I turn off the engine. One thing i did notice on the information center display the transmission temp is not displayed now. Any ideas?

Edit The AC works fine...

Edited September 17, 2020 by Wooderd
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Griff1500 · January 24, 2021

This thread came up while looking for my issue so maybe someone can answer my question before I take it to the dealership, I have the 4.3 v6 and my temp has always ran 160 or around that, recently I had the dealership replace a starter and did a leak test due to a evap leak code, well a day after getting it back I noticed my temp going up to 210 which it has never done, when I check if my fans are running I noticed only one is coming on, low speed with air off and turns up high when a/c is on but the other fan never turns on so I'm thinking that's why my temp is going up higher than normal, my question is should both fans be running especially when a/c is on, just want to know when I take it in so they don't try to b.s. me cause I have about a month left on the extended service contract and I'm sure they will try find any reason not to cover it.

MrMiller · January 27, 2021

I was having the same issue with the cooling fans being on full speed when turning off the vehicle. The temp gauge was pegged at the bottom at 160°F. I would have to disconnect battery to turn them off. This only happened intermittently with no clear reason for it happening. Dealer found a "stuck open" Thermostat and changed it out which they say is the reason for the fan staying on after turning the vehicle off. This was just today 1-27-2021. We will see if this takes care of the issue and I will update later...