Expert: Roland Finston - 9/26/2011

Question
Hi Roland, my wife 2002 Chrysler Sebring has been over heating for 3 months so I kept adding water to make minor trips around(10-15 mls). With a little knowledge, I changed, the radiator cap, thermostat,gave it a coolant flush and even add head gasket seal thinking it might of been a blown head gasket. However, none of those solution worked, the problem continued. With little knowledge as I mentioned, after all these months I didn't paid attention that the fans were not running. I located the fan relays, high and low and when I pulled out the one to the right when facing the box from the front of the car while the car was running, the fans came on and the over heating stopped. With that relay out the circuit the fans work and cools the car nicely but the check engine light came on and stayed on even if and when the relay is plugged back in. With that relay plugged in and they both are new, the fans don't work. With the relay out the fan run even when I plug it in when the car is on but when I shut the car off and restart it don't work. Any suggestions?

Answer
Hi Enoch,
My suspicion is that one of the fans is defective as regards its low speed winding and somehow that defect is preventing the fans from operating on either speed when the low speed relay is activated. The relay you are pulling is the low speed relay.  But that is just a guess. It might also be a problem in one of the 2 wires that come from the engine controller and when grounded cause either the low or the high speed fan relay to close its points and activate the fans. My inclination would be to disconnect the plug at the fan assembly noting that it has 4 wires and the wire numbers should be shown on the plug. You can then use jumper wires to ground pins 1 and 2 at the assembly side of the disconnect which are separate grounding wires for each fan. By ground I mean connect the jumpers to the - post of the battery,
Then use a third jumper, connected to the + post of the battery and touch the other end of that jumper to pin 3 (low speed operation of both fans) or pin 4 (high speed operation of both fans). It that test passes then I would check the wiring between the relay pins and the engine controller. Let me know if you pass the fan assembly tests and I can then tell you the wires to check for continuity between the relay sockets and the engine controller as well as the relay sockets and the fan assembly as any of those 4 wires could be the cause. If those pass inspection then the engine controller has somehow gone faulty.
Because the check engine light in 'on' from time to time that means there is a 'fault code' stored in its memory. A nationwide autoparts store, such as Autozone, will often give you a free readout of the codes. So try and get the 4-digit fault code number(s) and let me know what those are as another hint about what is going wrong here.
 Roland