Electric Rad Cooling Fan - After Run Question...

[Le S2 Audi]

The Coupe has been laid up for the last 3 weeks... The battery keeps going flat and I thought it maybe the same issue I had with the Golf... IE the head unit seems to like a switched and a non switched power supply... But not had time to sort it as I've had other stuff to sort first..

So yesterday decided to fit the DS2500 pads that have just arrived.... so whilst doing that I put the battery on to a trickle charge... then got down to doing the pads...

But As soon as 10 mins had passed with the charger in place... with the bonnet up and a wheel off the after run fan on the rad started to work...

Thought this has to be odd as the car hasn't even been started in 3 weeks... So now I'm thinking could this be the reason for the battery going flat?????

Anyone got any suggestions?? Could I have a faulty relay/sender unit somewhere or is this normal... Can't be surely???

What can I check???

[S2central.net]

Sounds like your thermal switch is faulty - and activating afterrun when not required.

Do NOT - repeat NOT - unplug the wires at the thermoswitch on the water rail as these are unswitched live wires that may or may not be fused depending on model year.

Try pulling fuse 21 and that should kill the afterrun pump.

If not ---> unplug the relay for the afterun pump that sits in the auxiliary panel above the drivers pedals - it is in position 14 and is numbered 324... This will disable the afterrun circuit completely.

Meantime order up a new thermoswitch.

[Le S2 Audi]

Cheers Paul...

Will do that tomorrow..

&

[s2driveruk]

can someone post a pic of the location in the aux rack...i couldnt see 324 the other week but i know my pump has run in the past

[johne]

Sounds like your thermal switch is faulty - and activating afterrun when not required.

Meantime order up a new thermoswitch.

Umm, need to think about this. Even if the thermal switch is permanently closed it should only run the fan for 10 mins or so as it triggers the timer in the after-run relay. There's been a mod suggested that you put a link or fuse across the thermal switch to make it trigger everytime you turn off the engine. If that works - and I see no reason why it shouldn't - it means that in this case the thermal switch can't be the problem.

The after-run relay itself could self trigger as the battery voltage dies away when you leave the car for a long time but I haven't heard anyone else have that problem. Certainly, I'd pull the after-run relay and see if that solves the problem but otherwise look for a battery drain elsewhere. Start by measuring the current "leaking" out the battery with everything switched off.

John

[johne]

can someone post a pic of the location in the aux rack...i couldnt see 324 the other week but i know my pump has run in the past

There's a diagram on S2Central.net showing where it is.

John

[s2driveruk]

think i have it but doesnt have 324 printed on the top - spare on its was south so should be ok now

Cheers
David

[nesshead6]

My fan always works when required temperature wise but only with the ignition on, could this be a faulty switch also?

[johne]

My fan always works when required temperature wise but only with the ignition on, could this be a faulty switch also?

Unlikely. The radiator fan on an ABY can run at three speeds.

Fan speed 1, the lowest speed and so low you'll have a job to hear it when the engine is running. This is the speed used by the after-run relay and the only speed that works with the engine/ignition switched off. If you have air-con, the fan will run at this speed when the compressor is engaged. Given that the after-run is rarely if ever invoked for most of us, you may find your fan never runs with the ignition off.

Fan speed 2, the normal speed the fan runs when it cuts in in traffic as the engine temperature rises. It a normal car under normal conditions, it's this speed that the fan will cut in and out at to keep the engine cool.

Fan speed 3, has been called the "On my god" speed. Never experienced by most of us and when the fan cuts in at this speed the load on the alternator is so high the engine almost stalls before recovering.

Fan speeds 2 & 3 are controlled by the thermo switch screwed into the bottom of the radiator.

John

[S2central.net]

Umm, need to think about this. Even if the thermal switch is permanently closed it should only run the fan for 10 mins or so as it triggers the timer in the after-run relay. There's been a mod suggested that you put a link or fuse across the thermal switch to make it trigger everytime you turn off the engine. If that works - and I see no reason why it shouldn't - it means that in this case the thermal switch can't be the problem.

The after-run relay itself could self trigger as the battery voltage dies away when you leave the car for a long time but I haven't heard anyone else have that problem. Certainly, I'd pull the after-run relay and see if that solves the problem but otherwise look for a battery drain elsewhere. Start by measuring the current "leaking" out the battery with everything switched off.

John

Tis a good point you make there John - a timer in the afterrun relay is supposed to limit the operation of the pump & fan to ~10 mins as you say (conserving battery in the event of a stuck thermoswitch). A faulty relay might not obey this rule though and just hold the fan on.

[veneto rs2]

Tis a good point you make there John - a timer in the afterrun relay is supposed to limit the operation of the pump & fan to ~10 mins as you say (conserving battery in the event of a stuck thermoswitch). A faulty relay might not obey this rule though and just hold the fan on.

Had the same issue last year on my RS2.

fan was on permanently at first speed with ignition off drain the
battery in half an hour.
All due to a faulty 324 relay/ECU

[Le S2 Audi]

Could my issue just be due to the fact that I had been re-charging the battery?

Brought the car to work this morning and there is no sign of the fan kicking in now!!

[Jamo]

I'd say this is the relay for the after run, I had this on my car after the engine swap, everytime connected the battery fan cut in.

Swapped the relay for a new one and issue was solved.

[GazzaG60]

is it a costly part.

think its to do with cars being laid up.

i have the same. also my windows wont always work. never an issue before car was not powered for a couple of months.