drewdrew

hey all, new to Mercedes, decent with other manufactures

2003 clk500

we had to do a radiator swap and flush, all went fine with that.

connected electrical to the original fan and couldn't get the fan to come on.

tested two primary wires and they came out 12v at the plug to fan box

didn't test control wires b/c air conditioning was set to cold

figured box was shorted when fan removed the first time

replaced with new fan and control box, no fan

was checking relay R "terminal 87 relay, engine (N10/1k4) with the motor off, key to run position.

pull relay R and the fan immediately goes to full speed!

dash lights up every warning and motor won't start, but that damn fan is on!

insert relay and fan off.... new relay and same behavior.

any thoughts? much appreciated!

Rudeney

The fan is electronically controlled by the ECU. It only runs when needed. If you put AC on max, or engine temp gets over 90C, it should run on high speed. Otherwise, it may run slowly or not at all based on cooling demands.

drewdrew

thanks! ac is on coldest, ect is well over 90c no fan

I checked every fuse including the massive 100 amp fusible link next to the battery and everything appears fine electrically

so there are four wires going to the fan control box.... what are the two small wires that go to the silver fan box?

the control wires from the ecu id assume... does anyone know what voltage I'm supposed to get from these when the fan should be running?

the two big ones are the 12v feed from the battery..

thanks for the help!