What's this switch for?

[simonwt]

I'm sorry to be asking what is probably a silly question...but I have recently acquired 72082640, a Big Valve Federal car.  This was the series of 100 done in Regency Red immediately before the first JPS cars.  Below the ash-tray on the console I have a mystery amber switch that lights up when turned on...but I haven't managed to work out what it's for!   Picture attached.  It appears to be original, but the Owners Handbook (which I have) does not show it, and the Workshop Manual says "Commencing at Chassis No. 72082684R..."  (i.e. 44 cars after mine...) the new facia has the "Fasten Belts" warning light in the same spot as my switch.   

Anyone know what the switch should do?

Many thanks
Simon

[BDA]

  simonwt!!!

That switch is not original to your car. On my car, and I think yours too, that is where the seat belt idiot light goes. You'll have to turn it on and see what happens or find the wires leading to it and follow it where it goes.

BTW, I have a similar switch on my car. It overrides the radiator fan controller. I would think that it is likely that it might be a similar thing to combat overheating.

[4129R]

That is a good place for any extra switches, or even a Smiths Voltmeter.

I will install fan over-ride switches, and that seems as good a place as any for them.

[simonwt]

@BDA.  The seat belt light was not introduced until after the first run of 100 Federal cars.  Mine is in that first run, so I wondered if this switch was some sort of Lotus fudge.   It is not (currently) a fan bypass, as my car has a separate fan switch under the dash next to the trip counter reset.  I will have to dig around behind the dash and see where the wires go I guess.   Thought I'd ask first in case this was an original item...sure looks like it...

[BDA]

I should have added that the original intent of my switch in that position was for driving lights that I never installed.

Good luck finding out what it does. Let us know what it is when you find it. It will probably be interesting to people here.

[simonwt]

Mystery solved!   As BDA so confidently stated, this switch is not original, although it is beautifully installed and has a very “Lotus” feel to it.   I managed to track down and speak to the PO before the P.O. before the P.O.   Turns out he had this switch installed to run a back-up electric water pump which is installed just below and behind the radiator.   He liked to take long runs and wasn’t willing to be stranded by something so trivial as a broken water pump.   It also turns out that the back-up pump is not working (!), so I will now spend some time checking ground wires and get that operational.   Thanks for the input...

[BDA]

There's been a lot of interest in electric water pumps. I would consider myself fortunate to have one!

[cwtech]

An interesting concept about installing a back-up electric water pump!  ....Not sure I can justify the reasoning.

If it is plumbed in series with the original flow, it could act as a restriction if not activated.

Almost all of water pump failures I have seen, resulted in coolant loss, so plumbing the back-up pump seems to have dubious merit.

If the coolant leaks into the crankcase, there are bigger problems.  ....If the coolant leaks externally, what does the pump, pump?

What am I missing?

[EuropaTC]

An interesting concept about installing a back-up electric water pump!  ....Not sure I can justify the reasoning.

If it is plumbed in series with the original flow, it could act as a restriction if not activated.

Almost all of water pump failures I have seen, resulted in coolant loss, so plumbing the back-up pump seems to have dubious merit.

If the coolant leaks into the crankcase, there are bigger problems.  ....If the coolant leaks externally, what does the pump, pump?
What am I missing?

For my money you're not missing anything. 

I think the sentence in bold is the key, if you get an instantaneous water pump failure whilst you're out driving then 99/100 it will be the mechanical seal and you lose water.  Where it might just save you is if the drive belt snaps and you realise what's happened before the engine overheats/bursts the mechanical seal. 

But you'd need to be quick off the mark to catch that, unless of course you had it automatically switching on whenever the engine is running.  In which case I suppose you might just as well discard the OEM pump and run 100% electric ?

[4129R]

Surely if the original pump fails, albeit from the pulley belt shredding (although it is not under much tension), then the original pump stationary would restrict flow substantially.

[Stuleslie]

My view is that the electric pump would be used to prevent overheating during stop-start traffic. As the Europa has a reputation for overheating while the engine ticks overs I would think that extra flow through the rad would be a good idea. The pump would have minimal restriction when not in use as the impeller would turn in the flow.

[jbcollier]

I have an Davis Craig EWP80 in series for just that reason.  It's a coarse-vaned, centrifugal pump that has virtually not restriction when turned off.   It's paired with the highest output fan I could find and a fan controller with a 50% duty cycle setting for the AC.  I also retained the stock rad fan switch which turns on both the EWP and the rad fan to high.  At highway speeds, nothing is on.  Tootling about town on a hot day, the fan controller will run the fan a low speed.  Sitting in traffic, the rad fan switch turns everything full on when temps hit 190/88.

[GavinT]

Interesting, John.

Where did you mount yours?
I’ve been contemplating a Davies Craig EWP80 and wondered if it mattered where it was situated.

In the front near the radiator is probably OK but I’m not sure if it wouldn’t get in the way there.
But since they’re quite small, perhaps mounting it at the water pipe exit of the backbone . . in that little lower area forward of the engine.

Alternatively, install near the exit of the existing water pump. I see the wiring diagram indicates the sensor needs to be at the thermostat housing.

Thoughts anyone?

[4129R]

The back up pump may not restrict flow, but the original pump, if it failed, surely would restrict flow.

Surely the problem in traffic is air flow through the radiator matrix to lose heat when there is no natural air flow through the grill. Wouldn't this be best solved by increasing the airflow through the radiator, rather than pumping faster hot water that cannot be effectively cooled?

A similar problem happens in F1 when the front drivers have to sit on the grid while the back of the field forms up.  Heat which cannot be lost by airflow through the rad.

[jbcollier]

The stock pump does not flow that much at idle.  The EWP80 flows a lot more, guesstimate of 3 to 4 times more.  Given that I'm going to be running AC, I think it is a good idea.