Cooling Fan Operation - 2.5

[rg]

Folks,

I've only got one fan in operation at the moment, the driver's side one,which cuts around 95deg C. I used to have both at around 92, but at a slower speed.

Where do the earths mount onto the body? I've identified the relay that clicks on at 95. Is this kind of fault a relay issue, or something to do with the control unit that is bolted to the battery box?

Any pointers welcome!

r

P.S. I've just found this thread:-

http://club-xm.com/forum/index.php?showtopic=4800

Does this apply to the 2.5, rather than the 2.1 mentioned in it?



This post has been edited by rg on August 22, 2010 10:40 pm

[noz]

Hi rg,

The 2-speed fan control is common across the range. There are two relays. They operate in conjunction with one another. The relays are brough in and out by the Bitron box which lives int he passenger footwell (AFAIR) which in turn senses the temperature via the brown sensor on the outlet tank.

I cannot remember now and its too late tonight to go and have a look but it goes something like this: When only one relay is activated the two fan motors are wired in series i.e. each fan only sees 6v since the whole 12v is dropped across two windings. With only 6v each, both fans turn at slow speed. When the second relay is energised (in conjunction with the first) then the wiring is changed so that the fan motors are wired in parallel and therefore both see 12v. At 12v the fan motors run at full speed.

If you have aircon then both fans will run at slow speed at all times if the aircon is switched on irrespective of the engine temperature. If the engine temperature rises above a preset level then they will change to high speed as described above. Once the engine has cooled they will revert to slow speed but will not go off as long as the aircon is on. If the aircon is off then the fans will stop.

The relays are mounted just under the slam panel at the battery side. They are subject to a lot of environmental abuse and tend to corrode badly where you cannot see. If you are having trouble the easiest fix is to drill out the three aluminium rivets on the top of the slam panel. This will release the bracket which the relays are attatched to . Once released the relays and bracket can be pulled clear of the slam panel so that you can see them and work on them. Clean up all of the connectors on the relays and the wiring and replace any which have badly corroded. once working just use a pop rivet gun to fix the relay bracket back to its original location.

Please let us know how you get on.

Cheers

noz

[miguels]

Noz...
Just a quick question...
Is quite normal on 2.5 TD that the cooling Fans stops when i switch ignition off????
Most part of the time when they are operating, i wait until they do the cooling cycle and stop to switch ignition off.
If it´s not normal, any of you guys knows the cause for it?

[noz]

Hi Miguel,

Yes, the fans do switch off when you turn off the ignition.

I have experienced the fans operating after I switch the ignition off, but this was due to a fault. I found this out when the fans drained my battery.

I hope this helps.

Cheers

noz

[Jan-hendrik]

On occasion I have had the fans running after switching off the ignition for about ten minutes when ambient and engine temperature were very high. But maybe that was due to a fault also

[robertmnorton]

H Jan,it is normal operation for the fans to continue running after ignition off with a/c cars.This was a regular occurrence in my experience with the hot summers in S France.
robertm

[techmanagain]

The 2 fans are (or were at the time of the issue of the DK5 information sheets) designed to have a post-cooling system, operating for a maximum of 6 ninutes when the temperature of the ccoolant reaches or exceeds 105 deg. C.

[Jan-hendrik]

QUOTE (techmanagain @ December 15, 2010 04:59 pm) 

The 2 fans are  (or were at the time of the issue of the DK5 information sheets) designed to have a post-cooling system, operating for a maximum of 6 ninutes when the temperature of the ccoolant reaches or exceeds 105 deg. C.

Of course, I knew that, didn't I?