I was wondering if anyone here knows if you can alter the temperature that the aux cooling fan kicks on at. I have replaced this fan as it was seized up a while back and I also swapped in the 180 tstat a year ago. Since then I have never seen temps go over 202 even in the summer heat. I know this fan kicks on at 212 degrees ( and if a bunch of other conditions are met). I believe this to be set in the Bosch ECU. Will any of the diag tools be able to change this value (e.g. Hawkeye, Autocom, etc?)

Why you ask? Since the engine temp is now cooler with the new tstat I think it makes sense to lower the starting temp of this fan. Also I would like to hear this spin every now and again to keep it from seizing up again.

Thanks for any help!

 

I'm in a similar situation, and I've been thinking about options. I have no idea if the ECU is reprogrammable with regard to this temp, but I'd be surprised.

You could rewire it so it is independent of the ECU. You'd wire it like an aftermarket electrical fan with an thermostat you put in one of the hoses. It would be tricky to dial in the correct temp for the fan to come on, but I think you could get the truck to running temp, then raise the trigger temp of the fan til it goes off. Then it will come on whenever the stock system isn't cooling enough.

The other option is to put it on a switch, and you just turn it on when you think it's necessary.

 

I suppose there is also the option of a manual switch via a relay to switch on the fan to override the thermostat if the temperature rises which will also 'exercise' the fan/fan bearing occasionally. This could be a lot more simple than risking reprogramming the ECU.

 

Just turn on the A/C. Once the compressor kicks in, the aux fan comes on.

 

^that^ it exercises every time you use the ac.
you can rig in a different thermatic switch to kick it on at what ever temp that you want, but you still want it to work with the ac. so that would need be addressed too.

 

I run my Climate Control on Economy most of the time, but every once in a while, I use AUTO or Defrost to work the A/C Pump and Fans, etc...

 

The fan doesn't come on every time you turn on the A/C. I believe it will not come on if it is colder than 77F or if you are going over 100km/h according to the rave.

Engine cooling fan control
While the A/C system is on, operation of the electric engine cooling fan, to assist refrigerant condenser operation, is determined by a combination of vehicle speed and external air temperature. When cooling fan operation is required, the ATC ECU outputs a cooling fan request to the ECM, which then energises the cooling fan relay. The cooling fan request is output if vehicle speed is 80 km/h or less while the external air temperature is 28 °C (82 °F) or more. The request is cancelled, and the cooling fan switched off, if either the vehicle to 100 km/h, or the external air temperature decreases to 25 °C (77 °F).

 

That's also my understanding as well. Road speed and external temperature are what initiates the aux fan start up on the AC.

I also regularly run the climate control on Auto during the winter to ensure the compressor clutch stays operational and the AC seals remain lubricated and don't 'dry out' which will cause the loss of the fridge gas. During the heat of the summer the AC remains on Auto climate control all of the time.

 

I mean I understand your thought process on this, but the bottom line is that a properly functioning clutch fan will have already removed the heat that you'd be looking to take care of.

Think of it in terms of when your thermostat opens, when the radiator becomes heat-soaked, and the lead time on the clutch fan to remove heat before tstat opens fully. The LR engineers factored all of this in when setting the aux fan actuation temps. A/C aside, that fan really shouldn't ever turn on if your clutch fan is there - at that point your tstat is wide open, dumping 100% hot water into radiator, even at idle your clutch fan should be able to dissipate a TON of heat in that state.

It's almost certainly due to their extreme climate testing (kinda like stupid intake heater) AND/OR for a failure mode of clutch fan if it were to freewheel. For those situations the stock values are perfectly adequate.


Changing them would risk having the fan turn on when the radiator/thermostat aren't even AT their potential heat dissipation rate yet, not to mention excessive current draw on alternator for no reason.

Besides, if you really leave your climate control on auto, the odds are that in most moderate/high heat days, the AC programming will be enough to trigger the fan anyways - in that respect you'll be able to check it fairly often.

 

Hi

The whole hypothesis is clearly explained in the initial AC description of the RAVE Manual where it describes the operation and parameters of the AC cooling system. It's very straightforward in operation as the checks and balances are all catered for in whatever temperature. I have never had any issues with mine in 11 years and 120K miles.