Under dash switch.... for fuel pump?

[davidpidge]

After fixing the mogs dynamo we took it for a drive. I was showing someone the under dash switch (which I believed was for the speedo back-light) but then then the car spluttered to a stop.

Turns out the switch had turned off the fuel pump!

Bit of headscraching before I realised what had happened. Am I going mad? Isn't the switch usually used for the speedo light? Did a previous owner create a nicely hidden immobiliser?

[alanworland]

Sounds like it - neet huh!

Alan

[ManyMinors]

I have owned a Morris Minor for several decades and cannot ever recall a time when I've felt the need to turn off the speedo lighting. Therefore, the switch should be ideal for that purpose
I fitted a fuel pump switch on my car too but I must admit that mine is even more hidden from view

[geoberni]

There are people who have used the Dash lighting switch for an isolator, either fuel pump or Coil supply.
Personally, I think it a very dangerous idea to use it for the fuel pump, as you yourself are now witness, the car will run for a while until the float chamber runs dry.
Imagine that happening to someone taking the car, or yourself because you've forgotten to switch it on when coming back to the car (distractions can happen) and it runs out as you're crossing a junction, or any other instance that results in you getting hit by something Big!
Much better to isolate the Coil than the fuel pump.

The only logical reason for the switch was to save about 15% of battery demand when parking with the sidelights on and try to keep a bit more to start the car.
Using the wattage given in the manual:
Side lights 4 x 6W, Number Plate 6-8W total approx 30W
Panel Lights 2 x 2.2W approx 4.5W
With far fewer street lights than we are used to having now, it was important to mark obstructions in the road as per the vehicle lighting rules.
In the older residential parts of the village where I live (pre 1950s bits), most of the street lights are Parish Council operated, not County Highways, simply because the PC installed them many decades ago, long before the County would bother.
It's why the ubiquitous after-market Parking Lamp was so common 1950s-70s. They met the lighting Regs but were typically a 3W lamp, instead of a possible 35W or so if using sidelights.

[davidpidge]

That makes sense. I did actually use the switch on one of my old mogs because I was constantly having battery issues when commuting during dark, wet mornings especially in traffic so I used to switch off the speedo light to save a bit of power.

[JOWETTJAVELIN]

The only logical reason for the switch was to save about 15% of battery demand when parking with the sidelights on and try to keep a bit more to start the car.

The main reason was actually to allow the driver to switch panel lights off at night to avoid unwanted glare on dark roads. I use the facility often. Various parking lights were available as extras.

Regarding 'secret switches' should the aforementioned scenarios play out, the insurance may not pay out as the result of an undisclosed modification.

[geoberni]

The only logical reason for the switch was to save about 15% of battery demand when parking with the sidelights on and try to keep a bit more to start the car.

The main reason was actually to allow the driver to switch panel lights off at night to avoid unwanted glare on dark roads. I use the facility often.

You may be right, I've heard that reason suggested before, but personally I don't think it holds up.
Imagine getting stopped by the Police for speeding and giving the answer 'Sorry officer, I'd turned off the Speedo Lighting so I couldn't see what it said...'
The owner's Operation Manual states where the switch is and what it does, but not why they fitted it.

Of course there is another precedent for your option; didn't they initially fit a little 'night-time' cover over the Indicator stalk lamp in case that nasty flashing green light annoyed the driver.......

A very valid point about Insurance and Fuel Pump Isolation switches

[JOWETTJAVELIN]

More roads were de-restricted then and there was no speed limit on motorways. Better cars had variable intensity panel lighting for the same reason. I would've thought that someone who claims to have worked on aeroplanes would know all about the effect of extraneous light sources on night vision.

[oliver90owner]

60-70 years ago things were much different to now.

Batteries were much more robust and of larger capacity. They would deep discharge without too much problem (compared to a modern automotive battery); starting handles were readily available, for starting with a depleted battery; dynamos were poor at replenishing the battery state of charge, so saving 15% of the battery drain was clearly a benefit. Battery chargers were likely much more common than nowadays.

Side lighting was 25W, at most (at 12V) - 4 x5W side lights + the number plate illumination (often 2 x 2W lamps). Not Minors, but many vehicles would have been fitted with other instruments, requiring further illumination, so the saving of night-time current drain could/would be a greater saving for those owners. TBH, most panel illumination could be controlled by the ignition switch, during the night-time, so I reckon the poor recharging system was likely the underlying reason for switching the panel lights.

Landrovers were fitted with a panel light. A lousy driver if one was unable to judge one’s speed, or switch on the display in a built-up area.

How many Minors, in the 1960s (M1 opened in 1959?) - not many were ever likely to exceed the 70mph speed limit, when that was eventually adopted in, or soon after, 1965.

The argument of dazzling the driver is a poor one. How many modern vehicles shut off the panel illumination? Some have a dimming facility -manual in older vehicles and mostly automatic in newer ones.

In the 1970s many vehicles could be illuminated on only one side, when parked. The indicator stalk was used to select the lamps to be illuminated. Around that time the legal requirement, for night-time illumination, within (at least) 30mph speed limits was removed - although many in cities parked, without lights, in quiet cul-de-sacs and/or under street lights before that.

[svenedin]

I detect anti-dynamo sentiments. The Lucas C40 dynamo can output 20 amps. This is more than adequate for a standard Minor. It is not actually the dynamo that lets down the battery charging (especially at night with the headlights on) but the voltage regular (RB106). A switch to an alternator gives a higher output but also a modern charging regulator. Personally I don’t want to see alternators under the bonnet so swapping the insides of the RB106 to an electronic regulator is an alternative solution. Some may know the quote attributed to Joseph Lucas, “A gentleman does not motor about after dark”

[geoberni]

I would've thought that someone who claims to have worked on aeroplanes would know all about the effect of extraneous light sources on night vision.

I had the courtesy to acknowledge your idea as a possible reason and you just have to be ... well 'You'... making personal comments.
Perhaps it's because I never reacted to you putting a Basil in your signature 2 years ago the last time we had a difference of opinion.
I'm sorry you can't have an adult conversation.....

[philipkearney]

Some may know the quote attributed to Joseph Lucas, “A gentleman does not motor about after dark”

An ironic quote from the 'prince of darkness' !

[svenedin]

Some may know the quote attributed to Joseph Lucas, “A gentleman does not motor about after dark”

An ironic quote from the 'prince of darkness' !

Exactly!