Nephew picked up a 2002 gt air need topped off. Turn on AC and the electric fan doesn't come on until high side pressure reaches 340 psi. I have done a lot of AC work over the years and this is a first for me. Is this normal?
Not normal. For the GT, the LOW speed fan should run ALL of the time that the AC is on. Based upon your description, I would say that the low speed fan is NOT working.
The SINGLE fan has TWO speeds. Low and high. There are several places that one speed can break down. The CCRM and the fan motor itself come to mind. The 2002 also has a circuit breaker for just the low speed fan (located on the right hand shock tower).