Dash Lights

[McMuttley]

As you will recall, I have been looking (or not) at my dash lights. I still am (not).

 

As a reminder, the lights for the dash, tacho and speedo simultaneously stopped lighting, however, the ammeter fitted with the alternator glows bright. The indicator and ignition lamps also work fine (as does everything else electrical)

 

It is the early 3A push/pull switch.

 

I can see no loose wires.

 

I assumed that rather than all 6 bulbs blowing together, it might be the switch (2H4841), but as the ammeter comes on via the panel light switch, I assumed that it must still work ?

 

Is this correct, or could the ammeter be getting feed through a faulty switch but not the dash or speedo

 

Annoyingly, the packet of replacement LED bulbs from China have gone walkies, so I wasn't able to check replacement bulbs.

 

I thought maybe all the bulbs are in series, but the wiring diagram suggests not all ?

 

Before I buy a new switch just in case and new bulbs, LED or not, just in case, any other thoughts ?

 

If I am testing current, what should I be testing??

• switch on off ?
• supply at any of the bulb holders (with switch on and off?)
• ? Do i put the red lead from the multi meter on the bulb holder and the black to earth ??

 

ps, other than china, who does the best value E10/987 equivalent ??

 

Thanks as always.

 

 

 

[Steves_TR6]

Afternoon!

 

All the dash bulbs are wired in parallel, in the diagram and i would expect in reality.

 

Im guessing that when the ammeter was fitted the wiring was altered to suit, i'd start here for failt finding.

 

You can test the bulbs by applying 12v to the positive feed to any one of them, they do need to be in place to get their earth.

 

Hth

 

Steve

[Fireman049]

Hi McMuttley ~

 

Have you checked that you have a proper earth for all the bulbs?

 

Tom.

[Don H.]

I have an ongoing and regular problem with the main instrument lights and one side of the center panel on my car too, Austin. Seems to be mainly due to grounds being opened and often fixed with scuffing contacts on the bulb or other ground point. My first bet for your issue would be continuity problems, not switch problems.

 

But I've also had problems with broken connections. Look carefully through your rat's nest for opens. They're sometimes tricky to find.

 

One of my tricker root causes was a sharp edge on a replacement headlight switch grub screw. The edge was sharp enough to cut the wire, and it took several instances of tracing an opened circuit to find it. Filed the clamping surface flat and no issues with that since.

[RobH]

Does 'old smokey' not have the standard rheostat for the panel lights Austin? If so then possibly that isn't working properly - perhaps the wiper not making contact. Its also possible the light in the ammeter has been wired direct to the lighting switch, so that still works.

[RogerH]

Hi Austin,

I thought the panel lighting on the 3A was similar to the TR4.

If so then 4 panel gauges have only two lights for illumination and not attached to the gauges.

The ammeter must be an after thought with its own bulb.

 

So move the panel away from the dash. Are the bulbs OK.

 

Also has the rheostat been turned to the OFF position. This will affect panel and dash gauges together,

 

Roger

[McMuttley]

Hi, its an early 3, so no rheowotsit, just pull/push

 

3 pairs of bulbs in each of tacho / speedo / dashpanel

 

yes the ammeter is new and has its own dedicated bulb. I originally wondered if it had been given its own supply, but it only lights up if the panel light switch is on

[RobH]

...So that probably means the panel light switch is OK but you have a dodgy power connection - or earth as others have already said - on the other bulbs.

 

From your original question - with the switch ON check for 12volts on the live side of one of the lamps (if the car is negative-earth its red meter lead to measure, black to earth as you say).

 

If there is 12v present but no light, then either the bulb is blown or it has no earth connection.

 

Since you will fiddling up behind the dash it might be easier to do the test using a spare bulb with flying leads rather than a meter though. One end of the bulb to earth and probe on the terminal with the other.

[stuart]

The panel lights are wired individually on single reds from the sidelight section of the light switch (First pull on switch) and the bulb holders earth the bulb with a tag down the side into the sleeve on the back of the steel centre panel. Often these dont get replaced properly into the sleeve and the earth tag isnt touching. You probably wont be able to reach the holders with the panel in place due to the proximity to the heater (another good reason to fit the smaller heater we have discussed previously)

Stuart.

[6TTR3A]

Take a look at my copy of McMuttleys photo. I made up that circuit on the bench & sure enough, it lit the secondary bulb but blew (all) the primary ones.

 

[Lebro]

Sorry, but this makes no sense.

The only way you would "blow" any 12V bulb would be to apply much more than 12V to it.

i.e 17V or more would eventually melt the filament.

It's for more likely (in Austins case) that the bulbs simply are not making contact.

 

Bob.

[McMuttley]

Well, still haven't got to this task, and with the Xmas period, I forgot to order spare bulbs!!! To respond to 6TTR3A, the lights did work (but were dim) before the alternator and ammeter were fitted, now don't and all 6 bulbs just went out simultaneously - so would it not be odd if all 6 stopped making contact at the same point ?

 

Will be venturing out to the garage on Saturday when the heater has kicked in !

 

ps

 

Olde Dimlylittly is still for sale.

[Lebro]

all 6 bulbs just went out simultaneously - so would it not be odd if all 6 stopped making contact at the same point ?

 

No, not really, it just suggests that there is a break somewhere in the wiring from the main lighting switch through the panel light switch to the 6 bulbs (7 in your case if ammeter has it's own).

 

Bob.

[McMuttley]

sorry, correction - 4 bulbs not working - speedo and revometer, plus the two instrument panel bulbs all dark, but modern ammeter (has its own built in bulb) glows, as do the ignition and flash lamps

[McMuttley]

in case its relevant, my main beam warning light works , but the speedo lamp doesnt

[Ian Vincent]

The main beam warning light is on a different circuit to the dash panel lights. It is fed via the dip switch circuits. Bob is right, look for the broken wire or loose connection.

 

Rgds Ian

[Lebro]

And anyway the speedo & rev counter have two bulbs each !, so that's 6 bulbs not working - all wired to the same place - the panel light switch.

Check this wire first.

 

Bob.

[McMuttley]

OK - sorted - having tested the currents they were fine either side of the switch and thereon along the in-sequence ( ? ) wire - it appears to be no more complex than every bulb had indeed simultaneously gone kaputz.

 

The problem with losing your mind is that you forget things.

 

The reason that I couldn't find the packet of LED's appears to be that someone had fitted them (deffo not me) , or at least I assume this melted mangled mess were, until recently, LED bulbs ?

 

 

 

Did they melt as whoever had fitted them for me didn't add any sort of capacity/resistance thingamy ?

 

Anyway, Bromley's Halfords remarkably had GLB987 bulbs (although only 4) and they 'glow' like the north star (on a foggy night)

 

 

 

Now to cleaning the instruments (well the glass) - - - - As always - one job leads to several others !!!

 

I am aware that the dial face will be very delicate, so I will do no more than a gentle blast away of any dust with a camera cleaning blow spray and very gently brush (maybe not even the latter).

 

Is this task of cleaning the glass as simple as unscrewing the bezel and accessing the glass from the front of the panel without taking the instrument out ?

 

(please say it is)

 

 

(TR3a for sale with working instruments / lights)

[Don H.]

I've always taken out the instruments, Austin, before taking off the bezels. If the instruments are clinched down reasonably tightly, it seems a lot easier to free them from the dash panel. You might not need to remove them all the way, but at least loosen the U clamps on the back of each gauge. The bezels mount with a sort of bayonet mount, BTW, and in the original installation had square-section O-rings between gauge and dash. The bezels themselves had a gasket material between dial face and bezel, to keep out dust and prevent rattling one assumes. These generally crumble if they're still the original ones.

Edited December 30, 2016 by Don H.

[RobH]

It looks like those LEDS had been fitted into the SES (small Edison screw) bases using hot-melt glue. Not a good plan perhaps?

[Lebro]

Perhaps the LED's were the wrong polarity, & had a protection diode in the base - that would draw lots of current, get hot, & melt the hot meld adhesive.

 

has the polarity of the car been changed since the led bulbs were fitted perhaps ?

 

Bob.

[McMuttley]

well having replaced all the bulbs, removed and cleaned all the bezels and domes and cleaned the dial faces and the crappy plastic strips round the sides that don't stop dust but do block light... I have to say that it has been the least rewarding / LEAST BENEFICIAL task I have ever carried out on the car.

 

[Lebro]

:P