My '03 XKR was running well until yesterday when the overheat light came on just piddling around the neighborhood. I got her home and noticed that the fans weren't running. Coincidentally (?) the A/C stopped blowing cold at the same time which the diagnostic showed as low freon.

I just so happened to be playing with one of the Bluetooth OBD sensors at the time and it shows engine cooling temps as normal, although I'm not sure I have the Torque app totally nailed yet.

Any help appreciated.

 

You really need to get this resolved quickly as it only takes one real overheating event to cause a lot of expensive issues.

The fans are operated by the ECM through a couple relays mounted down low near the radiator. The temp sensor reports to the ECM.

If the car is really overheating the thermostat is the most likely villain.

 

Had somewhat of the same problem - I never saw or heard my cooling fans run ever.

The following was response from WhiteXKR and I thank him for it.

Quote:
Originally Posted by billm
Yesterday the Wash DC area hit a new record high of 85. That all said, after making a brief stop mid-afternoon, shutting down the engine (max 10 mintues) and restarting, the engine seemed to stumble/run rough when backing out of the parking slot. Had to hit the gas to get it to smooth out. No Codes were thrown on the Odometer and no CEL indication. The temp gauge as always, was mid-range (it never varies more than an 1/8" when up to temp, summer or winter). The Temp Gauge as everyone knows is just a 'placater' and gives no indication of engine overheat or higher temp, until it is possibly to late.

I have never heard the cooling fans running (when the engine has just been shut down) or seen them turning (with engine running and the hood open) when the engine was at or seemed to be above normal operating temp.

Is there a handy power source in the engine bay that can be jumped to provide power to the fans, to see if they will spin up? Is there anyway to check the thermostatic controls to the fans, to see if they are working and within temp limits?

Would hate to fry the engine because of the Temp Gauge and/or the cooling fans not working.


Quote:
From White XKR
Get a 100 ohm resistor at Radio Shack for a buck or so. Unplug the coolant temperature sensor (grey 2 pin connector on coolant pipe). Place the resistor across the 2-pins on the connector on the harness. This will simulate an overheat condition to the ECU...you will see a warning in the car and the fans should turn on. Ths is better than just testing the fans because it checks the whole system (except the sensor). If the gauge rises normally during warmup, the sensor is likely fine.

Keep an eye on my website...I will have a module that will convert the gauges to read real data available this spring.


I got the 100 Ohm resistor from Radio Shack (6 pack for $1.19), jumped the female pins at the harness of the sensor. You do not need Test Leads or anything. Just bend the Resisitor Wires to fit into the harness.

The Heat Guage went immediatly to Hot, got an Odometer Screen Warning and both of the fans came on. The fans also cycled from low speed to high speed. Which tells me everything is working fine, other than maybe the Cooling Temp Sensor. Thats the next thing, I will probably just replace it with one from the Dealer. That way I know that I will be getting something with the correct 'temp limits'.

 

Ok, thanks BillM and WhiteXKR, I got a 100 Ohm (1/2 Watt) resistor and plugged it into (I hope) the right sensor. Just on the other side of the pump from the thermostat? It immediately went to hot but no fans came on. Even after shutting down I could hear a "whirring" sound. I plugged it back in and it started with gauge showing cool. Anything else I can try?

 

It would appear that you have connector/relay/fan motor issue. The resistor should have turned both fans on. Could the 'whirring' sound been the fan motors energized but not turning? Can you manually turn the fan blades?

 

I'll give that a try. Are there any "expected" fan failures? I'm wondering if I was operating with only one fan for awhile and didn't realize it until the other one went.

 

Bill you need to check both 30 ampp fuses in the engine bay fuse box for the fans by the washer fill. Swap the relays around to check them too. Both fans should come on low with ac on. Orrrrr....... You can just come by and see me again

 

Lol, believe me I want to, I'm just scared off cooking the engine. Maybe I can do it in 2 mile hops - see you next week. I'll try the fuses/relays. Thanks!

 

Ok, both fuses checked out okay, and I swapped the relays around with no effect. Fans still not coming on. Can I try anything else?

The retaining clip on the harness connector for the temperature sensor snapped off nicely...argh. Anyone got a part number?

 

So the fan relay seems to be the culprit. Beginning with the 2003 model, that is integrated into the fan unit (argh). New one on order.