2014 GMC Sierra high speed fan do not turn on

[Nicster]

I have a 2014 GMC Sierra 5.3 120000 and I noticed the Temp was staying at 160° with the fans running all the time this past week. I used my scanner to clear code and shut fans off. I replaced the thermostat, temp sensor  and reservoir tank (found a crack and was leaking on reservoir) now I noticed it stays above 210 line and it gets to 235°-240° when I am towing and want to keep going higher in temp and why wont my high speed fans turn on. 

[Ravenkeeper]

On 5/22/2022 at 7:03 PM, Nicster said:

I have a 2014 GMC Sierra 5.3 120000 and I noticed the Temp was staying at 160° with the fans running all the time this past week. I used my scanner to clear code and shut fans off. I replaced the thermostat, temp sensor  and reservoir tank (found a crack and was leaking on reservoir) now I noticed it stays above 210 line and it gets to 235°-240° when I am towing and want to keep going higher in temp and why wont my high speed fans turn on. 

Mine wouldn't run if the AC was in AUTO, had to manually set the fan.  Couple days later, it cleared itself, have never had a repeat of it since.