I have an 02 Peterbilt 379 with C15 cat engine fan clutch Hello 2004 Peterbilt 379 cat c15 mbn I just noticed oil leak coming from behind the fan clutch and it's making a mess in front of the engine, I'm wondering about the source of 5/5(10) Engine fan for 1998 379 pete | Page 2 | TruckersReport Engine fan for 1998 379 pete Discussion in 'Peterbilt Forum' started by Cindy, Jul 24, 2012. Page 2 of 3 < Prev 1 2 3 Your truck has fuses and relays behind the dash for the engine fan. I have attached a diagram for you. engine fan relay | The Truckers Forum I have a 1998 peterbilt 379 3406e cat. The three relays inside the dash, on the one relay for the fan number 85 is the ground, and that wire is a 239, the 86 on the relay and that wire is the 522 is called fan disable, and the 87 is the fuse 10 amp and thats number 220 wire, and the 30 is ignition power fuse thats a 226 wire.