Where is the high limit fan relay switch on a 1991 Chevy Silverado?

[lacrymosa1981]

All settings on the fan work except the highest. Can you tell me where the relay switch is for that high setting?

 

[Chirvs]

under hood on the passenger side underneath the black cover. It looks like a big T. Its underneath. Its one on the relays not sure exactly but it should be labeled on the under side of the cover.