Instrument Light Brightness Switch

[HarryFD]

My new to me 1971 2+2 came to me a few months the ago.

While most of the car was in great shape, it was running very rich. My local Jaguar guru was able to get that resolved with minimal fuss. He reported no issues of concern to me.

Another minor issue was that the toggle switch that controlled the brightness of the instrument lights was jammed in the dim position. Fearing that if I took the switch apart to repair, I would be unable to fix it, I ordered replacement from SNG Barrett. It was installed with no drama.

I decided to take the old switch apart. After gently removing the front of the switch, I found that the white plastic toggle had be jammed to the side and a contact was bent. The two switch tetter-totters were intact. After putting all the parts in their proper places, the switch is now functioning as designed.

My take away, the next time a have a switch issue I will attempt a home repair first as it seems pretty straightforward.

[bitsobrits]

Fortune favors the brave.

[Marcusu]

Just out of interest, where do you find the instrument dimmer switch on the dashboard?

[Craig Balzer]

The switch is a simple 3-position one: off-dim-bright
Just left of the headlight switches:

[malcolm]

The switch is a simple 3-position one: off-dim-bright
Just left of the headlight switches:

If it's anything like mine was, the three positions are "Off, almost unnoticeable, dim"

[Craig Balzer]

the three positions are "Off, almost unnoticeable, dim"

Absolutely correct.
Historical research has revealed that Lucas was responsible for the first intermittent wiper, too.

[Craig Balzer]

I got to thinking about your question regarding a dimmer switch.

There is actually another dimmer on Series III's (may be also on earlier series, just not that familiar with them).

This photo from the 'net shows the US driver's footwell.



There is a stubby black knob down in there at shin level; just above the chromed bolt that holds the radio tower in place. It controls a rheostat for the dashboard gauges - I just don't remember which ones.

Here is the back-side of that knob:

[Marcusu]

Thanks for the replies all.
It’s interesting that the U.S cars have a secondary dimmer rheostat knob in the footwell.
I have a mystery switch under the dash on the right-hand side of my RHD New Zealand market car, see photo.
I thought it might be either a dimmer switch or trip reset for the speedometer. Does anyone know what it might be?

[Redman]

Pretty sure it's the trip reset. Only turn it anticlockwise!

[Marcusu]

Thanks Gordon! I’ll give it a try.

[AussieEtype]

If in doubt, read the instructions

[HarryFD]

I got to thinking about your question regarding a dimmer switch.

There is actually another dimmer on Series III's (may be also on earlier series, just not that familiar with them).

This photo from the 'net shows the US driver's footwell.



There is a stubby black knob down in there at shin level; just above the chromed bolt that holds the radio tower in place. It controls a rheostat for the dashboard gauges - I just don't remember which ones.

Here is the back-side of that knob:

I just looked under the dash of my 1971 2+2 coupe with AC and did not find a rheostat in the location indicated.

[malcolm]

Are you sire that's not a foot dip switch for the headlights?

[Bob.]

Later handbooks clarify.
The OP has a 1971 ('early') car so won't have the supplementary control in the footwell. The parts manual shows the rheostat it but doesn't identify the change point when it was added.

[Craig Balzer]

Bob

A much better description and photo than mine.
Well Done!

[Bob.]

Looking deeper, it seems that this dimmer was added to LHD cars in early 1972, but it wasn't fitted to RHD cars, which just got a blanking plug to fill the new mounting hole.

[AussieEtype]

but it wasn't fitted to RHD cars, which just got a blanking plug to fill the new mounting hole.

The early RHD (1971) cars did not even get the mounting hole, let alone the blanking plug.

[Bob.]

Neither did LHD.

[Heuer]

[MarekH]

That service bulletin is just telling you when the resistor changed from one mounted using stand-offs into free air versus one mounted on a ceramic base instead. This already appears on the post 14 Parts Manual diagram above the clocks as it is well before s3 production.

The bulletin isn't saying anything about a rheostat, when it might have been added or whether that replaces the fixed resistive dimmer option. In any case, you'd probably want the dim and dimmer panel light options to instead be bright and brighter as it isn't Jaguar's finest design feature. It's almost as wonderful as the custom relay used to power the two stages of brightness rear screen heater orange indicator bulb.

kind regards
Marek