Guess what I have.....Hint: 3 Watt instrument bulbs.

[RickM]

Finally in from Germany. My next door neighbor's nephew is a car nut/engineer over in Germany (the Eifel (near the Nürburgring)). He was able to source the elusive BA7s based 3W/12V bulbs.

This weekend I'll start to conduct some simple tests to present to the crowd.

The following tests will be conducted for new Bosch 2W bulbs, new 3W bulbs and my 20 year old OE bulbs :

- Individual current draw
- Light meter readings (In and/or out of guage??)
- Visual impressions/pics

I'm trying to decide on an appropriate power source for the test as I'd like to conduct indoors. I'll also have to source a light meter...I think dad has an old german one .

From there we can attempt to calculate load capabilities of the dash harness.

Cross your fingers.

[Rick Lee]

I want a set!

[304065]

Rick,

No matter what, the factory's dash harness is pretty weak. It's a finer gauge, like 18 or so, and there's no fuse. Any retrofit solution should go to a lower gauge wire with better power handling capability and a fuse for safety.

[RickM]

Originally posted by john_cramer
Rick,

No matter what, the factory's dash harness is pretty weak. It's a finer gauge, like 18 or so, and there's no fuse. Any retrofit solution should go to a lower gauge wire with better power handling capability and a fuse for safety.

Agreed. Don't want to present a possible "solution" that introduces a fire risk. Let's get some values together and see what we have. Should at least be interesting.

While we're at it I'm hoping the bulb socket is capable of the increased draw.

[rfuerst911sc]

I am interested in the results please keep us up to date.

[john walker's workshop]

me four. i'll deal with the wire size, regardless.

[jester911]

Yep,
I would love to be in if it works.

[steve911]

Count me in too.

[Early_S_Man]

RickM,

The instrument illumination bulb Black/Blue wiring is 0.5 mm^2, or slightly smaller than 20 ga on the AWG chart ... as shown below:




My suggestion for bench testing is to use a variable 0 - 20 Volt power supply, monitored by a good digital multimeter, and set the variable supply to the same as your system Voltage -- measured above 2000 rpm with the headlights on ... which tends to run higher [14.5 - 15.0 Volt range] than most earlier cars! You could build a variable power supply with parts from Radio Shack ... a 24 Volt transformer, bridge rectifier, LM317T regulator chip, and a handfull of other parts should fill the bill!

For a light meter ... I would suggest a Gossen Ultra-Pro with Fiber Optic probe.

The bulb sockets won't be a problem, as you are only going from 142 mA at a nominal 14.0 Volts ... to 214 mA. My suggestion for wire size would be 16 ga. There really isn't a fire hazard here with the additional load, but an upgrade should be over-engineered to give the best illumination and reliability. It wouldn't hurt to incorporate a 2.5 or 3.5 Amp circuit breaker into the new wiring loom.

One step in the upgrade should be to clean all of the bulb socket's body with automotive white polshing compound ... to get rid of any oxidation or corrosion, and give the best possible grounding, which does depend on the friction fit in each instrument! You can clean the receptacle for the bulb holders in each instrument by positioning the gauge face up, and apply polishing compound with a Q-tip, scrubbing the sides thoroughly ... followed by isopropyl alcohol on Q-tips as well.

[derek murray]

I'm in...

[BOOMER]

Sweet, I've seen the light........ me too

[RoninLB]

Originally posted by RickM

He was able to source the elusive BA7s based 3W/12V bulbs.

Bingo

[david914]

I'm in for a set!

BTW, I'd be more concerned about the capabilities of the dash illumination rheostat than the wiring. The stock ~20 AWG wiring will support the additional load, but without knowing the details on the dimmer, I'd proceed with caution. A simple dimmer circuit could be installed to handle the extra load if need be. It could be driven off the stock rheostat.

[buttjoint]

Where do I sigh up?

[scottb]

I'm in for a set.

[Jack Olsen]

Build a better (or at least, brighter) mousetrap...

I'm in, too.

You should sell a bulb-and-fuse-set combo.

[smestas]

I'm in for a set!

[thabaer]

Before I opened the thread, my guess was burned-out dash light wiring and curled PC traces

Do you guys really have trouble seeing your dash ?? I usually have my dimmer turned down 1/3 or even 1/2.

[Shaun @ Tru6]

I'd love to see my gauges at night. Count me in.

[TRE Cup]

Definitely interested!
thanks
dave