Cooling Fan Hi/Low issue

[AZRaptorJohn]

Trying to diag a cooling fan or A/C issue and looking for y'all help.

While driving A/C performance is ok but not great. One issue I just recently discovered is my boss has the same truck but his fan go into Hi mode while mine never do. I pulled relay and jumped the Hi mode and it began to work. Thinking maybe the relay was bad I replaced it but didn't resolve the issue and looking for y'all input where else I need to check.

 

[Guardrail]

Maybe your bosses truck has a problem. I've seen where the AC is over charged and causes the Hi mode to kick in. It has to be in the High 90's outside before I hear mine kick on. The best way to check is to put a scan tool on it and see if the PCM is commanding the HI mode to come on. If it commanding Hi mode and the fan doesn't come on you have a problem.

 

[pat247]

When starting my Gen 1 I turn the key to the run/on position wait 3 seconds then start. If I start it without the wait period quite often I have no fan control.