Aircon/Electric fan operation query

[andykem]

Hi,
Got a 1990 760GLE V6 with the B280 engine and ECC aircon system. The car also has an electric cooling fan in front of the aircon condenser to supplement the usual belt driven radiator cooling fan.

Last year sometime (I think it was), with the bonnet up, I noticed that the electric fan activated whenever the aircon compressor was switched on. This seemed like normal behaviour, as the same thing used to happen on a Peugeot 405 I had for a while. I was told that this was to enhance the effectiveness of the aircon producing cold air inside the car by taking more heat out of the condenser. I guess this would apply most when travelling slowly or stuck in traffic.

Just recently I noticed that the electric fan wasn't behaving like that. So voltmeter in hand I checked things out a bit. I found the relay controlling the electric fan didn't work and when I took the cover off it found there were dry solder joints, fixed those and, by connecting the terminals of thermostatic switch in the radiator proved that the relay and fan worked.

According to the wiring diagram in Haynes there is also a wire that connects to the ECC control unit (495). And that leads to the question I have:-

As matters stand, just local trips and the aircon not on for that long, I still do not observe the electric fan kicking in whenever the aircon compressor clutch is switched like I once did. Can someone say how this should operate? Perhaps it only happens once the system somehow recognises a particular cooling condition that needs the extra effect provided by the electric fan? Or, does anyone think there is still something wrong because it ought to act every time the aircon comressor switches, like on my old Peugeot?

Thanks for any thoughts,
Andy

Originally Posted by andykem

Hi,
Got a 1990 760GLE V6 with the B280 engine and ECC aircon system. The car also has an electric cooling fan in front of the aircon condenser to supplement the usual belt driven radiator cooling fan.

Last year sometime (I think it was), with the bonnet up, I noticed that the electric fan activated whenever the aircon compressor was switched on. This seemed like normal behaviour, as the same thing used to happen on a Peugeot 405 I had for a while. I was told that this was to enhance the effectiveness of the aircon producing cold air inside the car by taking more heat out of the condenser. I guess this would apply most when travelling slowly or stuck in traffic.

Just recently I noticed that the electric fan wasn't behaving like that. So voltmeter in hand I checked things out a bit. I found the relay controlling the electric fan didn't work and when I took the cover off it found there were dry solder joints, fixed those and, by connecting the terminals of thermostatic switch in the radiator proved that the relay and fan worked.

According to the wiring diagram in Haynes there is also a wire that connects to the ECC control unit (495). And that leads to the question I have:-

As matters stand, just local trips and the aircon not on for that long, I still do not observe the electric fan kicking in whenever the aircon compressor clutch is switched like I once did. Can someone say how this should operate? Perhaps it only happens once the system somehow recognises a particular cooling condition that needs the extra effect provided by the electric fan? Or, does anyone think there is still something wrong because it ought to act every time the aircon comressor switches, like on my old Peugeot?

Thanks for any thoughts,
Andy

I think you've still got something wrong there because the secondary rad with it's fans you are on about should cut in at all times because it is a heat exchanger for the entire system. How long ago did you have the air con checked ? because it may be a system which shuts down if there isn't sufficient refrigeration gas in the system. Why don't you wire it constant so the fans are on all the time regardless to using the air con system ? You will then be sure they're on.

Personally hate air con it uses up fuel and less it's serviced often is a waste of money.

Charlotte

[andykem]

Thanks for reply Charlotte,
The aircon actually does work OK although it's a couple of years nearly since it was regassed. It's just that I'm aware that they are more effective with the condenser radiator given some extra cooling by a supplementary fan.

So, what I'm trying to establish is whether the electric fan should be switched at all times when the aircon compressor operates or whether, being Volvo, there's a greater sophistication in the control system so it only operates when either the system, weather or both are 'hot enough'.

From what you've said it should be just the simple 'all times' option; and so, it looks like I need to carry on looking for a fault.
Thanks
Andy

[penninepullman]

My electric fan has never run at all times that compressor is engaged. It has only cut in when requesting about 18degC in a 30+degC ambient temp.
Most of the time the engine driven fan gives sufficient cooling.

The 760s with ECC have several coolant temp sensors. For the ECC there is one near heater matrix. (Others are ones for fuel injection system and the gauge on the dashboard.)
Found that my copy of genuine Volvo wiring diagrams has errors(!), which, of course, Haynes reproduce.

[TheJoyOfSix]

The cooling fan on my 760 would only ever cut in if the AC was having to work hard to cool the car down, usually just after start up if the car had been parked in the sun on a very hot day. If the car had recently been used the fan wouldn't cut in as the interior temps hadn't risen that high.

It should also cut in if the coolant temp rises too high as there's a sensor in the radiator to tell it to do so. I assume this is a supplementary cooling system for the coolant as well as the refridgerant.

[andykem]

Thanks all,
I think, on balance, taking it all in the round, and not really wanting to get any more in amongst the wires and things anyway(!), I'm going to assume that all is now well and it'll work when/ if the Volvo ECC brainbox decides it's time.
Cheers,
Andy.