Thread: Aircon on 300Tdi Defender

Originally Posted by JamesH

Hi

When it is working properly (it isn't at the moment but that's another matter) I can have my aircon on in peak hour traffic and tootle around the city and it has no real effect on the temp gauge. But when on a country run and thundering down the road at a gobsmacking 100kph, the aircon starts to push the temp gauge up. It climbs to about 75-80% and then I reckon that's far enough and switch off the aircon, the temp gauge soon sinks back to normal levels.

The gauge never moves otherwise and quite happily sits on 50% all day everyday and only ever moves when I try and run the aircon and maintain highish speeds.

Is this a fact of life and I should live with it. It would be a pity becasue it is on the long runs when you'd like to close the windows and vents and have some cool air.

It shouldn't do, - is it the combination of both (ac and high speed) or does it happen with either (high speed or ac).

Have you got condenser fans on your vehicle, if so is it/are they working - if you don't have one/two - then get one/some fitted.

If you have one/two and they are not working get them fixed.

Also you may want to get the AC checked out for pressures a high head pressure = high condenser temp.

At high speed (wow 100 kph) the compressor is working harder/faster and creating higher head pressures.

Plus of course the external fins/coils could be blocked with dirt/leaves etc.,, a good pressure wash helps here.

So check to see if the coils are blocked

Check to see if the condenser fans are working

If that is all okay then get a techie to check the pressures.

Hi, thanks for reply.

No it is strictly the combination. One or the other of conditions alone does not tend to be a problem.

I believe the electirc fan in front of the radiator comes on with the aircon but I will double check this.

cheers

Originally Posted by JamesH

Hi, thanks for reply.

No it is strictly the combination. One or the other of conditions alone does not tend to be a problem.

I believe the electirc fan in front of the radiator comes on with the aircon but I will double check this.

cheers

Also make sure its blowing in the right direction, I have seen a few trying to 'suck' not blow.

If it's working then give the coil/radiator a good clean with a pressure washer on low pressure.

Thanks again. Your second idea makes sense to me even though I am no techie. I will do as you say.

cheers

Hi James
Most pressure cleaners will stuff the fins if held close and do no good at distance.
Ive got a brass tap fitting with a small hole in the end.You only need the hose turned on half or less does a wicked job.
Look in the tap fittings section of bunnings,it just clips onto the standard hose clips.
Andrew

just my 0.02c worth, but have you tweaked the fuel pump by any chance ?
If so, this is where your problem may lie.

The cooling system is marginal with a full blown tweak of the fuel pump, and the condenser restricts the air flow to the radiator, without the air con even being on.
When I refitted the condenser to my 'fender back in October, the running temp climbing hills pushed up 2-5*C without the air conditioner running
The fin spacing of the Sanden condenser appears to be too fine (too many fins per inch) creating a 'packing up' of the air and restricting flow through the radiator.

This backs up what an old friend who was a development engineer at JRA on the Perenties told me years ago. They increased the fin count on the radiators and had overheating problems which went away when the fin count was reduced ( fin spacing increased)
Theory says that if you increase the primary surface area of a heat exchanger you increase the heat rejection factor. No one told the 110's. Practice dictated otherwise in this case

Also, the Defender relies on the viscous fan at speed, ram air just doesn't cut it. Part of the reason lies with what I discussed above, and I suspect this is partly to do with poor underbonnet airflow.
It appears that the air that has already gone through the radiator can't readily escape out of the underbonnet area, creating a high pressure region and reducing the airflow through the radiator. It won't go in if you can't get it out
GU Nissan Patrols also suffer from this malady. Luckily you can overfill the viscous hub on them to engage the fan more often, overcoming the problem. Defenders and Patrols appear to need the fan to push the air out from around the engine rather than draw it through the radiator. A dodgy viscous fan in a Defender will show up with overheating at speed, particularly on hills (or with the air con on)

Thanks everyone for the good responses. Rick I have not tweeked the fuel pump (I considered it at one stage but my innate conservatism told me to leave it alone) and when I had the engine out after the prang I got the cooling system restored but still everything you say has a logic to it and I will get the performance of the viscous fan checked out.

I know what you mean about airflow under the bonnet. You only have to driver with the window and vents open and ten close the vents to feel how it effects air coming into the cabin.