After Run Coolant Pump (V51)

[Alex C]

I understand that the after run coolant pump is supposed to run whenever the engine is switched off regardless of coolant temp. However, my pump doesn't always run when i switch the engine off. And for vehicles with air conditioning the pump is controlled by the Fan Control Module rather than a relay near the steering column.

Often the pump runs when i get in the car in the morning and turn the ignition one click; it hardly ever runs, if ever, after its been driven

To try and track down the cause i have;
Checked the fuse on top of the battery which can burn out: I have pulled it out and it is looks fine
I've checked the HVAC module on VCDS for faults with none stored

When the pump is running:
I can earth the positive pin of the pump power supply to the inlet manifold and i see 12V on the voltmeter

When the pump isn't running:
There is zero voltage across the pins
There is zero voltage when i earth the positive pin to the inlet manifold

From the above:
it isn't a faulty pump
it's not a blown fuse
it's not a dodgy earth
it is the power supply to the pump

As the pump gets its power supply from the Fan Control Module (J293 - part number ending 506K) - does this mean it has to be this control module thats faulty or does the FCM module control power to the pump based on some other input signal?

I cant find a self study guide that really covers the after run coolant pump; SPP208 seems to make a cursory mention of the after run coolant pump before quickly moving on

have i overlooked anything??

 

[Alex C]

...have i overlooked anything; looks like i need to check fuse 16:

http://workshop-manuals.com/volkswa...king__continued_coolant_circulation_pump_v51/

 

[nobbybonez]

i had similar issues, intermittent running, not doing the full ten mins, changed the pump and all good again, runs every time. i think mine may have been connections internally in the pump.

 

[Alex C]

when my pump isn't working it's because there is no power to the pump; there is no voltage across the two pins in the plug. And the pumps is new from only a few years ago

some people have managed to fix dodgy pumps by cleaning the brushes on the pump motor

 

[<tuffty/>]

No power to the pump suggests its the fan control unit... fans work on low speed ok when AC is on?

My pump was intermittent much like nobbybonez's and a new pump fixed that.. well... it did fall apart first prompting the change in the first place but up until then it was intermittent

If power is getting to the fan control unit and the low speed fans work then it could well be the control unit as this is what switches it on/off

<tuffty/>

 

[Alex C]

I think low speed fans work OK but I'll have to check; so low speed fans are on if AC is on

Was wondering where the Auxiliary 'time parked' signal came from and if its somehow passed though E87 to the FCM (J293) as a 10min after run signal; but i rekon if that signal wasn't being passed through E87 properly (if its supposed to be) then it would trip a fault code on the HVAC?

I'll try a new/second hand Fan Control Module and see what happens

 

[vanilla_ice]

I think low speed fans work OK but I'll have to check; so low speed fans are on if AC is on

Was wondering where the Auxiliary 'time parked' signal came from and if its somehow passed though E87 to the FCM (J293) as a 10min after run signal; but i rekon if that signal wasn't being passed through E87 properly (if its supposed to be) then it would trip a fault code on the HVAC?

I'll try a new/second hand Fan Control Module and see what happens

View attachment 109588

Not sure if you are still about @Alex C, but did swapping the fan control module fix your issue?

 

[vanilla_ice]

Bump - Has anyone else experienced the same symptoms as @Alex C ?

I read one theory that the control module cuts off power to the pump if it detects an issue. I.e. too much resistance. Any truth in that?

Thanks