Turbo water pump: does it ever cut in whilst driving?

[Paul 290T]

Hi,

From my testing it appears that my relay does not pull in the water pump if I short the lead that goes to the water temperature switch. It could be the wiring from switch to relay of course. However I've tested the wiring continuity between the plug that goes onto the thermo switch and the relay socket in the fuse box and it's been ok.

The feature that gives a 30 second pump run after switching off the engine works every time.

As you probably know the thermo switch is designed with two functions:

1) To extend the pump run period after the engine is switched off until the coolant falls below a preset temperature
2) To start the pump whilst driving if the temperature exceeds a second higher temperature.

In practice has anyone ever observed if the pump cuts in to extend the run over period from engine off or if it cuts the pump in whilst driving?

Regards

 

[TTM]

I recall Tony "944Turbo" mentioning he recorded the pump being triggered when running the car under intense use - track day.

 

[Diver944]

Yes I remember Tony wired up a light in the cockpit to come on when the pump did, and sure enough it illuminated during hard use on track

 

[Lowtimer]

In the absence of rigging up some sort of light, how would anyone know? Surely it would be undetectable while driving.

 

[Paul 290T]

I agree, you'd never know if the pump runs whilst driving.

I think I'll rig up an LED as Tony did. Might prove that my relay is ok, or not.

I suspected that track use would be the only trigger whilst driving. It'll be interesting to see what i find.

Thanks for your support.

 

[944Turbo]

Hi, I could get it to trigger but only by letting the temp go up to almost where the fans cut in (stationary) and then booting it through the gears. I used a dummy alarm led (flashes when connected to 12v) and just connected the negative side to the sensor, I think I picked uo +12v from the ashtray light. It was quite a hot day when I was testing it as well. In normal use even on trackdays it didn't run.
Tony

 

[Paul 290T]

Hi 944turbo,

Thanks for posting your findings.

I was going to wire an LED in parallel to the pump, that would have tested the whole system, I already know the pump is ok. I'm suspicious of the relay.

But if i connected to the sensor then i could test that too. Thanks for suggesting the alternative connection.

That said, from your findings unless I move to a much hotter country I probably won't see the sensor change state anyway.

Regards