Gauge lamp dimmer control TR4A

[TrRob]

From the TR4 workshop manual:

 

Illumination of the tachometer and speedometer is controlled by a switch at the left side of the tachometer.

 

Is that the same for a TR4A and where is that switch located? (i only have the TR4 workshop).

The gauge illumination lamps are not connected by mine TR4A and according the wiring diagram I have

these are connected to the gauge lamp dimmer control.

 

regards

Rob

[Geko]

on 4As all instruments lamps including tacho and speedo are connected to the dimmer switch

[peejay4A]

...and the dimmer is located in the switch plinth.

[RogerH]

....and the dimmer switch goes from - dim to dimmer to off.

 

Not the best device after 50 years of iffy wires and dicky contacts.

 

Roger

[Grahamgl]

I dismantled the one in my car,cleaned the contacts and, now it works perfectly.

Graham

[peejay4A]

....and the dimmer switch goes from - dim to dimmer to off.

 

Not the best device after 50 years of iffy wires and dicky contacts.

 

Roger

Mine's shiny and new with new wires and works. Sort of.

[TrRob]

Thanks

[Geko]

Not sure if I'm opening a can of worms in resuscitating an old thread but mine never worked properly, not even the brand new one. It's always been the "0/1" sort of thing but no real progressive dim. The next mission is to see what's inside and try to make this work.

1/ The threaded part is bent so I'm going to straighten it and put it back perpendicular to the housing (2)

2/ The hexagonal rod (3) is coming off just as if there's nothing to retain it inside. Surely it must be sealed somewhere either with a circlip or sealed to one of the parts i.e. (5) ? Part missing?

3/ Shall I remove the resistance (1) to clean it or just brush it gently in situ?

4/ How do I test the resistance to see if the dim effect is the expected one - while the switch is dismantled?

 

Thanks for your advice

Edited March 14, 2016 by Geko

[AlanT]

You a want Scotch-brite pad. Look on ebay. Made in UK by Mirka I think.

 

This will quickly brighten all the metal bits.

 

I would not mess with the resistance winding unless its not joining up to the teminals.

Just buff the tops where the contact hits.

[Geko]

Scotch brite I have, so that's one done...

[RogerH]

Hi Stef,

the centre contact area needs to be cleaned thoroughly as does the brass sweeper that sits on it.

As Alan stated do not remove the resistance coil - simply clean the area where the sweeper arm makes contact.

Make sure the external contacts are clean.

 

If you put a resistance meter on the external contact and the end of the of the coil then you will get zero at one end and the full resistance at the other. If you run the lead along the coil the resistance will vary in a uniform manner.

 

Having spent ages doing a deep clean your lights will now be enthusiastically dim.

 

What is required is a brightener.

 

Roger

[Geko]

Thanks Roger, I think i found the fault: With the wear the arm of the sweeper tend to bend upwards hence not providing a frank and steady contact with the resistance. I bent it downwards so that the contact is frank throughout. I guess the spring (4) will need to be strengthened.

Edited March 14, 2016 by Geko