Temperature gauge spiking

[Dpond855]

Hello all newbie here. I have a 2011 GMC Sierra 1500 WT V8 and on hot days the temp spikes. I noticed that the fans are only working when I run the defrost or ac. Can anyone tell me what might be happening here. The dealer has replaced the thermostat twice and changed the coolant once. Why they didn't see the fan not working is beyond me but now the warranty has run out so I'm left to do this on my own. Any thoughts would be appreciated.

Also it's a dual fan set up and they both run during defrost or ac selection other than that they don't run at all

 

Thx

[sdeeter19555]

Are you sure it's heating up...temp sensor?

 

Was the rad cleaned inside and exterior?

 

Sent from my SAMSUNG-SM-G900A using Tapatalk

[Jsdirt]

Fans will only come on WITHOUT the A/C on if they need to - meaning the coolant temp is getting above 220° (or thereabouts). It will start out at a low pulse-width modulated speed. If the temp climbs higher, the PCM commands them on full duty cycle - full speed. They will run anywhere in between depending on coolant temperature.

 

If the engine temp is below the fan temperature threshold, they will never come on.

[Justin101714]

Well, if they work when the a/c is on means the fuses, relays and ground connections are okay. Shouldn't be any circuit concerns either. The ECM controls these as well. Possible ECM concern

 

 

Sent from my iPhone using Tapatalk