mikeloos

I have 2 radiator fans on 1990 vette but only 1 seems to cycle. What temperature starts the second one. Car operates at 240 degrees sometimes

rodj

Turn the A/c on and see if 2nd fan runs

Churchkey

90 white shop manual seemed vague as to when & how the secondary fan operates. Mine did not run when the AC was in use.

I installed a jumper wire to connect the two relay ground wires so that both fans start @ 228* or start when AC is selected. The AC works better (colder, sooner) & engine temps remain close to normal in traffic.

The fan relays are on a common bracket attached to the left side of the fan shroud.

I used insulated male/female butt connectors in the ground jumper wire. Connect in spring, disconnec in fall.

coupeguy2001

I would believe that the 2nd fan is supposed to run anytime the A/C is selected under 35 MPH.
You need to check out fan relay + wiring connector to see of it is compromised somewhere along the frame.