Does anybody know how the cooling fans on an A/C equipped v8 are actuated?

I've got a pair of electric fans to fit to my Disco to replace the viscous unit. I also have air conditioning. I have heard the condenser fans operate without the A/C switched on. This suggests to me that they are thermostatically controlled. Can anyone confirm this? If so I could take a feed from the feed to the fans to actuate a relay to bring the main fans on.....

sidewaysste said:

I've got a pair of electric fans to fit to my Disco to replace the viscous unit. I also have air conditioning. I have heard the condenser fans operate without the A/C switched on. This suggests to me that they are thermostatically controlled. Can anyone confirm this? If so I could take a feed from the feed to the fans to actuate a relay to bring the main fans on.....

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They operate in 2 modes:

1. Air-con mode - in this mode the air-con is turned on and off as the air-con system requires. This means that when the weather is below 27°C they don't normally come on.

2. Engine protect mode - in this mode they will come on if the engine ECU detects a possible overheat situation, to give extra cooling.

Hope that helps

Dave

thebiglad said:

They operate in 2 modes:

1. Air-con mode - in this mode the air-con is turned on and off as the air-con system requires. This means that when the weather is below 27°C they don't normally come on.

2. Engine protect mode - in this mode they will come on if the engine ECU detects a possible overheat situation, to give extra cooling.

Hope that helps

Dave

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I don't know what book you have been reading biglad, but none of this info is applicable to a 3.9 D1.

You would be better picking up a thermo switch and fitting that to operate your fans via a relay

discool said:

I don't know what book you have been reading biglad, but none of this info is applicable to a 3.9 D1.

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Bûgger, Bûgger, Bûgger.

I was thinking DII - sorry to all (hangs head in shame)

sidewaysste said:

I've got a pair of electric fans to fit to my Disco to replace the viscous unit. I also have air conditioning. I have heard the condenser fans operate without the A/C switched on. This suggests to me that they are thermostatically controlled. Can anyone confirm this? If so I could take a feed from the feed to the fans to actuate a relay to bring the main fans on.....

Click to expand...

Yes they do but as you may or not know but that on a very hot day with the ac on the V8 engine and engine bay becomes very hot, therefore the fan system is designed to switch on, via the sensor screwed into the thermostate housing, if or when the engine bay gets excessive hot when the vehicle has stopped and engine is switched off, although I've never had this even when the engine bay is bloody hot after a run.

Also if the engine temp goes into the RED zone the ac is designed to cut out and resume operation when engine temp returns to normal.

I sure you do know that info as it's in the owners handbook and Rave.

Your replacement fans will require a engine coollent temp sensor.
The trouble with any retro fitted electric fan, is that unless you require the fan to continually run when normal engine running temp is reached the temp sensor will have to be rated above the engines normal running temp. Therefore the engine must geta shade hotter than its normal temp, is this wise with the 3.9 all alloy engine? i'll let you decide.

Have a look at the Kenlow fan instructions for setting up the fan and you will see what I mean

thebiglad said:

Bûgger, Bûgger, Bûgger.

I was thinking DII - sorry to all (hangs head in shame)

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That will be the posh AC system then

Next question - does anyone have copies of the bit in the owner's handbook or rave?
Or the kenlowe instructions? I don't have any of them.

Also does anyone know what temp the coolant temperature switch closes?

sidewaysste said:

Next question - does anyone have copies of the bit in the owner's handbook or rave?
Or the kenlowe instructions? I don't have any of them.

Also does anyone know what temp the coolant temperature switch closes?

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I have originals of all three but u will have to Google, TOPIx is the LR site also http://www.landy.pl/LandRoverDiscoveryWorkshop1995-1996.pdf

Sorry bud I'm obviously having a stupid day - I can't get the link to work and and I don't understand what you mean by TOPIx

Topix is LRs site is for owners handbooks among a few other things, and the link is a PDF so you will need Acrobat software to open it.