Changing light bulb in speedometer - help

Gauge lights are all powered by black (ground) and yellow (dimmer rheostat). You need my drawings, dude. Gently pulling on the housing the wires go into will remove the bulb. Bulb numbers in the manual are cryptic. I'd suggest removing a bulb and reading the number printed on it.






_____________________________
Ferrari 308 Wiring Drawings
http://www.ferrarichat.com/ferrariads/showproduct.php?product=1036

 

Steve,

On the Speedo the bulbs that illuminate the face of the Speedo are the two bulbs at approximately 3 and 9 O’clock. The three on the bottom illuminate the idiot lights in the lower face of the Speedo (blinkers and something else I forget…… high beam indicator?.). The bottom center one may also illuminate the Speedo face but I just do not recall. Replace them all as even the new replacements, albeit higher output and better than OEM, are still a little too low in wattage output. In the other gauges I just replaced the face illumination bulbs as the idiot light bulbs worked just fine. This left me a a small bench stock of future replacement bulbs.

Back to the Speedo. Look carefully at the white plastic piece that enters the back of the Speedo for each bulb. It is actually two pieces; a white socket/plug which holds the bulb and which is connected to the black terminal on the end of each wire, and a white ring which holds the wiring and contacts inside of the well for each socket and bulb. Pull gently holding the upper white section and the two white pieces should separate, leaving the white ring attached to the aluminum back of the Speedo and the bulb and socket should be out and in your hand. I used needle-nosed pliers with cloth rapped around them to prevent scratching to start separation and a jeweler’s screwdriver to slowly pry the socket the final rest of the way out. Worked like a charm.

Also here is the thread where I posted the links for sourcing the bulbs.

http://www.ferrarichat.com/forum/showthread.php?t=185212&highlight=bulbs

See Post #11 and Post #12 but I suggest you read the entire thread. Good stuff in there.

For the last fix here. Recommend you remove the two wires going to the dimmer rheostat and splice them together (you have already removed them to get the cluster out). The OEM dimmer rheostat is so poorly made the thing drinks juice by the volt even when it is supposedly in the “Full-Bright/Zero Resistance” mode. The resistance is terrible; in the order of several volts. It is probably the single-most “problem area” causing dim dash lights. Just shim or solder the two dimmer wires together and insulate, replace your bulbs with the higher watt replacements sourced above and “Ta – Da !!!!!” Brighter Lights!!!

Comparatively speaking, have your sun glasses handy !!!

I finally found the European replacement for one of the two bulb types (the big bulbs; the other-than-Speedo replacements) but have yet to find the replacement lights for the Speedo here in Germany. I’ll keep looking and when I find them I’ll post both vendor and part numbers for my non-North American friends who wish to do this fix and get the parts locally.

Hope you can follow this. If not, post again and I’ll try to be more clear.

Mark

 

I stand corrected; twice. I wrote the above from memory, NOT from looking at the back of my Speedo. Sorry.

1st Correction:
Now Reads: On the Speedo the bulbs that illuminate the face of the Speedo are the two bulbs at approximately 3 and 9 O’clock. The three on the bottom illuminate the idiot lights in the lower face of the Speedo (blinkers and something else I forget…… high beam indicator?.). The bottom center one may also illuminate the Speedo face but I just do not recall.

Should read: On the Speedo the bulbs that illuminate the face of the Speedo are the two bulbs at approximately 3 and 9 O’clock. The three on the bottom illuminate the idiot lights in the lower face of the Speedo, directional blinkers and Parking Light Indicator.


2nd Correction:
Now Reads: Back to the Speedo. Look carefully at the white plastic piece that enters the back of the Speedo for each bulb. It is actually two pieces; a white socket/plug which holds the bulb and which is connected to the black terminal on the end of each wire, and a white ring which holds the wiring and contacts inside of the well for each socket and bulb. Pull gently holding the upper white section and the two white pieces should separate, leaving the white ring attached to the aluminum back of the Speedo and the bulb and socket should be out and in your hand. I used needle-nosed pliers with cloth rapped around them to prevent scratching to start separation and a jeweler’s screwdriver to slowly pry the socket the final rest of the way out. Worked like a charm.

Should Read: Back to the Speedo. Look carefully at the white plastic piece that enters the back of the Speedo for each bulb. It is a one piece socket/terminal which is connected to the black terminal on the end of each wire. Pull outward and twist gently back and forth. The white piece should separate enough to then slowly pry it out of the aluminum back of the Speedo. I used needle-nosed pliers with cloth rapped around them to prevent scratching of the white plastic socket and start separation and a jeweler’s screwdriver to slowly pry the socket the final rest of the way out. Worked like a charm.

Very sorry for the confusion.

Mark

 

thank you

 

Walter, this thread has good information, but it's also over 13 years from the prior post to yours - some good things have changed in that interim! Now, many if not most of us working on the instrument lighting for the 308 are switching to LED bulbs in the gauges, which are both brighter and draw less voltage than the old incandescent style bulbs. Your forum searches should turn those up pretty quickly -

I'd highly recommend going the LED bulb route if you're going to the trouble of removing your instrument panel already.

Cheers,
Gordon