speedo lights and clock

shanon

shanon

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howdy all,

Need some help determining why my speedo lights don't work. Flasher indicator works, but cannot get speedo lit. All other gauge lites work.
Bulbs look good/clear/clean, even replaced/tried a different speedo, but get same results.....dark.
I wish the ol' stock dash VDOs were as bright as my new VDOs... :shock:

Can I change bulb watts?? Gotta good source for bulbs?

Also, how do you tell if the clock is really dead, tried two different units, can't get them to work (light works). Is this a direct wire to the battery or ??? Bizarre ground set-up?????or just take them out for skeet practice....(ie: quartz conversion)

TIA!
-shanon
'70 2800cs
 
Speedo lights: a gray cable feeds each of the bulbs in each instrument. Only one wire per bulb, the ground is locally provided by the bulb socket making contact with the metallic body of the instrument. If the tachometer bulbs work then the gray wires are getting voltage, so my bet is that the ground is disconnected from the speedo body. Ground should be a brown cable (probably triple cable) connecting to the back of the speedo. I think that the turn indicator socket gets two wires and that is why it works fine without the speedo ground.

Regarding bulbs, I upgraded to 4W bulbs using the vanilla Silvania bulbs. They are a bit longer than the originals but fit fine.

Finally, for the clock the only thing it needs is 12V and ground. If lights work you know you have ground. The 12V is different so go measure that. Next thing is to take the clock out and open it up. There are two or three failure modes, all easy to fix, except if you have a sealed clock. Don't hurt them, we can fix them.
 
thanks for tip Arde!

works now- think it was a combo- bad ground and funky old bulbs.
some bulbs were brighter than others after tests. I made a direct ground with a fresh wire and swapped out some bulbs from a spare dash i had. Decided to switch all the gauges too. the spare Euro (Kph) gauge set ended up being 6 mons older (5/69) but in better shape with no hazy lenses. also, the brightness looks much closer to the new VDOs........sweet.

.... and the 240Kph speedo looks pretty cool too!

thanks again-
-shanon
'70 2800cs (re-Euro'd)
 
I installed the new 4w bulbs and had good luck too. My problem is the blue high-beam light which can be barely seen. I moved up to a 7w bulb and it is still hard to see. Oh well. Maybe I'll rig up some blue LEDS in a bundle.

On my glove box light I did a 6-LED combo replacement and it is produces a really neat and bright glow. I may do the same on my trunk and hood lights.
 
Curious, I went to Kragen and got new bulbs today to see if they would make a difference.

Are the Sylvania #1893s the 4w bulbs you speak of?
There is no watt indication to the package. These are a bit longer as Arde described.

FYI-don't push the longer clock bulb in too far/completely, it'll push in the clock face.

-shanon
 
Mine are Sylvania 3893, designated "European Lamps" and have a T4W
in parenthesis. Also got them at Kragen.
 
thx Arde, glad I didn't open the other pkgs!

About the clocks, I went thru the repair sequence from the CS Registry w/o any luck (tried it on both my clocks). One had the contact closed, the other was open, if that helps........ Got any other ideas up your sleeve while their handy?

:roll:
-shanon
 
On the clocks the one with the contact closed is likely to have an electrical problem, and for me that is easier. I would:
- measure continuity a) at the solenoid and b) between the 12V and GND contacts. If have a) few ohms and b) no continuity then you have either a wire or PCB connection problem. Easy to fix.

If b) has continuity and nothing happens when you apply 12V then it could be a mechanical
problem. I'll be happy to try my luck if you give up.
 
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