Radiator cooling fans inop

[Alex Martin]

Hey guys, i have a 2005 gmc yukon with electric fans. It is the 5.3 and the electric fans will not turn on. I have replaced the coolant temp sensor and the relays and it is still inop. If i send 12v to the fans they will turn on and constant power is getting too the two 4 prong relays my tools will not fit to test the 5 prong. None of the fueses are blown either and relays have resistance to them. It has a slight hickup on startup but not much of one and sadly no they do not work with the ac on the temp will go straight past 210 when parked 

[davester]

Test that power/gnd is getting to the right pins of the relay socket, and that putting power to the output pin of the relay socket.  If they all are good, then put in a new relay and see what happens.

 

If you can't directly test the pins in the relay socket, you may be able to access the backside of the relay socket (I know on my truck, if it were part of the fuse panel under the hood, it flips up for access to the backside and you can more easily probe that side), or get something that will fit in the socket that you can test.