My brother has a 99 Discovery 2. The radiator fan (condensor fan)comes on when he turns the a/c on, like it should. However, when he doesn't have the a/c on and the temp starts getting hot the radiator fan doesn't come on. I believe the radiator fan should come on when the temp gets toa certain level, correct? If so what controls when the electric radiator fan to come on? The coolant temp sensor?

 

if its not comming on thats a good thing... the coolant has to get very hot for that alone to turn on. wont do it under normal opperating conditions, sometimes when offroading youll see it, and occasionally if you let it sit fora long time with it running

 

His trk has a "clutch" fan that runs off the water pump. Open the hood and on the front of the engine you will find a big fan, it spins when the engine is running. It spins at a slower rate than the engine until the viscous unit gets hot then the clutch inside it locks up and the fan spins at the same speed as the engine, when the viscous unit cools down it un-locks and spins at the slower speed.
In a overheat situation both the clutch fan AND the electric fans will run to try and keep the engine from overheating.
What you are thinking of is like a front wheel drive car where they have to use only a electric cooling fan because the engine is in the engine bay sideways and it is impossible to run a clutch fan off of the engine.
In this case the fan is turned on and off by a coolant temp sensor.
His trk is normal.

 

My Rover runs around 190F off road. Even after hours of wheeling it does not come on. It really depends on outside temperature and humidity. If you want to know what your Rover runs at coolant temperature wise, get a Scangauge. It will tell you everything you want to know.

Cheers,

Pete

 

Well the problem is that it will overheat running at idle with the a/c off. With the a/c on it doesn't run hot or overheat due to the electric fan being on. It won't overheat if the electric fan would turn on but without the a/c regardless of temp the fan doesn't come on.

So my question still remains does the CTS control when the fan comes on without the a/c on? That is why I asked if the CTS controls when the fan comes on because the fan won't come on without the a/c being on.

 

You need to not worry about the fan and find out why it is overheating, the radiator on a DI is big enough that it could idle all day without a fan and never overheat.
I am betting that he needs a new waterpump.
And yes, the electric fans should come on without the A/C being on in a overheat situation.

 

Sounds like a bad temp senser. Have him get this fixed before he toasts the engine.

 

This may be a good time to install a new thermostat and flush the coolant.

Cheers,

Pete

 

I put in a new t-stat for him and flushed the radiator. I bled the system etc. It won't overheat with the a/c on and it can idle all day. It will overheat at idle with the a/c off. So the only difference is that the electric fan is off. The reason I don't think it is a waterpump or rad. is because it won't overheat with the a/c on. So my guess is that the electric fan isn't coming on when the a/c is off causing it to overheat at idle. The waterpump flows the same whether the a/c is on at idle or not.

 

I would have to say then that the viscous unit on the clutch fan is bad. And you are right, the water pump spins at the same speed at idle, A/C or not.