afterrun pump wiring

[adam g]

I need to wire up an afterrun pump onto my ABY engine. Its in a WR chassis and Im not using the ABY loom so need some advice on how to wire it up. After a quick search on here an easy solution would be to run it off the same live as the fan. But aren't these only supposed to work when the engine is switched off? would there be any harm in it kicking in every time the fan does? Thanks.

[Evilgoat76]

Try
Here

[vertigone]

By the way Someone could explain when it is suppose to run please ?
In which conditions ? (regarding water t° I suppose ?)

[Evilgoat76]

That I wouldnt mind knowing either

[johne]

There is a thermoswitch attached to the water manifold under the inlet manifold. It has an activation temperature of 105 degree C. If at the point you turn the engine off this switch is closed or it closes subsequently, the after run water pump is run for 10 minutes along with the radiator fan at fan speed 1, the lowest speed.

There is a tolerance on the switch so depending on your switch, it may close at 103 or 107 degree C. In my case, and in the case of many on here, the temperature never gets high enough to trigger the after run relay so although it works, on my car it's never operated for real.

Some have changed the thermoswitch for one with a lower operating temperature (off a LT van IIRC) or just joined the wires at the switch in which case the pump and fan will run for 10 minutes every time you stop the engine.

John

Oh, and the wiring diagrams are on S2central.net

[vertigone]

many thanks johne

[adam g]

I checked out the link to S2 central and it states the pump circulates the water in the opposite direction to the usual coolant flow, so I guess I cant just tap into the radiator fan circuit in case it opperates when the engine is running. Why would Audi do that I wonder, I could just swap the inlet/outlet pipes over but I imagine the engineers at Audi did it for a reason.

[johne]

I checked out the link to S2 central and it states the pump circulates the water in the opposite direction to the usual coolant flow, so I guess I cant just tap into the radiator fan circuit in case it opperates when the engine is running. Why would Audi do that I wonder, I could just swap the inlet/outlet pipes over but I imagine the engineers at Audi did it for a reason.

Audi wouldn't want to place a pump in the main large bore circuit because it would be expensive & limit the flow when it wasn't working and be cut off when the thermost was closed so they put the pump in the heater return circuit as that makes for a smaller pump - one that's also used on washing machines I believe - that isn't defeated by the thermostat.

The pump isn't directly in the coolant flow for the turbo so the flow from the pump is set so that it reaches the turbo as directly as possible. That happens to mean that it's the coolant flow through the turbo that is reversed from it's normal direction when the engine is running but of course the turbo doesn't care, it's still being cooled.

I suggest you use the ABY top hose with the "T" in it and tee into the heater return circuit and put the pump in there, the same as Audi did and use the timer relay to control this.

You might also want to consider my earlier post - for many of us, this pump never runs so if you don't do track days and don't mind letting the engine idle for a few minutes after any good thrashing you won't get any benefit from going to the trouble & expense of fitting it.

John

[Audi-Porsche Avant RS2]

Some very good 3D

http://www.s2forum.com/forum/showthread.php?t=4070

http://www.s2forum.com/forum/showthread.php?t=15565

Alessio

[adam g]

That makes sense, thanks for the reply. The one aspect I am still struggling with is how to ensure the pump can only activate when the engine is switched off. Other than the temp sensor I will be starting the wiring from scratch. I guess I will need a timer relay to supply the 12v but how to ensure it operates with ignition off only I don't know. I could hook it up to a manually operated switch.

I intend to do away with the auxiliary radiator so assume the temperature will be high enough to activate the pump from time to time and might go with the lower temp switch anyway. It did sometimes get boring letting my old 10v tick over for a couple of minutes after an enthusiastic run so its worth fitting I think.

[S2central.net]

Use the factory wiring for afterrun pump for 3B or ABY as your guide... sourcing the factory timer relay won't be hard either. The control logic is a bit weird as the afterrun pump is actually tested for a few seconds when you 1st turn the key on - nearly everyone thinks this lil whirring noise the fuel pump waking up, but its not.

I have the auxrad removed and can easily build up enough heat soak after shutdown from some heavy traffic to invoke the afterrun pump so its deffo worth while.

PS - great explanation from johne there... Top drawer info !