One of the lamps for my speedometer is out on my 79. What's the change out procedure?

Thanks

 

Cuss a lot before beginning then cuss through the whole job. It's a miserable job every time you have to pull out the dash panel . Everything including the main dash wiring harness is crammed into that small space making it difficult to get the dash back into place.

 

Before you pull the dash, take a look under there first. You might just be able to do it (possibly). I just went out in the shop and looked underneath mine. You can see the grey wires and the bulbs on the back of the speedo (if you pull the duct that's there).

I can touch the rubber socket. I'd recommend a head lamp instead of a flashlight, because you're going to need two hands under there and there's no room at all. You'll be on your back, feet on the ground, shoulder blades on the floor in front of the driver's seat and arms up into a spot, that makes a fruit crate, look like a studio apartment.

If it's the bottom bulb you're lucky, because it's going to take one hand to hold the rubber socket and one to push and twist the old bulb out. And this with a bunch of wires, vacuum hoses and cables everywhere, in very cramped quarters.

And You're gonna have to be careful, not to mangle anything and relax and take your time, because at times those old sockets are so mangled, that the hot copper wire is hanging out the back. Not an easy task.

Easier than pulling the dash (which, really, really sucks, believe us). A group of us, agreed that we'd all rather pull the motor out of the car, than pull the dash...

 

Not an immediately helpful answer. Whenever you do remove the drivers' tach/speedo dash board...look at all the individual little light bulb assemblies protruding from the inside firewall wire harness with their gray wires. Cut them off. With the dash safely out of the car, stick the light bulb assemblies back into the speedo/tach surrounds. Make a wire harness and wire them all together and make a single connector. Next, look at all the cut off gray wires protruding from the inside firewall wire harness. Join them all together and make another connector. When you re-install the harness there will be a male/female harness connector hanging down from the tach/speedo and another female/male harness connector hanging down from the wire harness. Just simply snap the connectors together.....no fuss about trying to install individual lamps.
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Agreed that working under the driver's dash board is really one of the worst places. If You've some extensive work to do..like changing from manual brakes to power brakes, or factory power brakes to Hydroboost power brakes..it makes a lot of sense to remove the steering wheel column. It's not that difficult, and with the column out of the way, everything becomes just so easy.

 

disconnect the speedometer cable from underneath by pushing on the tab and pull (not easy). remove the lower bolts and drop the steering column slightly, remove the screws and pull the speedometer/tach assembly out some, the bulbs are on a printed circuit sheet in small twist out holders. i would replace all of them while in there since they're all old... good luck. more detailed instructions below...

http://willcoxcorvette.com/instructi...ng_removal.pdf

 

You can do it setting in the drivers seat. Remove screws and remove clear plastic cover. Remove allen screws holding black plastic trim cover surrounding tach and speedo. Remove tach and speedo mounting screws and pull out tach assembly. You can pull the speedo out far enough to disconnect the cable. Now the bulbs are accessible. Some bulbs you can pull out with your fingers, On some bulbs you can put some black tape on the jaws of long nose pliers. Be careful with those plastic trim parts. They are fragile. That's what I did on my 79 C-3. However that really didn't solve the problem. It turned out the flex printed circuit board behind the instrument cluster had some bad copper pathways. Willcox to the rescue with a new part. The instrument cluster had to come out, but with some judicious maneuvering of the cluster, I was able to get it out of the dash and without dropping the steering column.
Good luck.

 

i just did this last weekend on my 79!

relax, it's not hard or miserable. here's what i did:

on the clear plastic cover, take note of the 2 different screw sizes, and where they go. remove them and the clear cover. you'll need a shorty phillips driver for the ones above the steering column.

remove the 4 allen bolts that secure the speedo itself. the tach stays right where it is. if you have tele wheel, move it to it's lowest position, and put a cloth over the steering wheel hub.

no need to get all cramped up trying to unsnap the speedo cable from under the dash. too crowded!

pop the hood, move over some wiring/hoses to provide access to the speedo cable. unscrew the threaded connection that secures the speedo cable in place, then push the speedo cable/speedometer assembleage rearward. this will require you to push the cable rearward and pull the speedo rearward, alternating. the speedo will move rearward prob 6 - 8inches, and will drag on the cloth you put over the steering column hub. no scratches! : )

now you can unlatch the speedo cable and remove the speedo itself. carefull of the needle!

i had 4 out of 5 bulbs burned out, so i replaced 'em all. my GM service manual and my owners manual both listed a 1891 bulb. that is incorrect, wrong socket. you probably will find #168 bulbs in there, as i did. that's what i installed, four have simple access. one is in a recessed pocket, i used a padded needlenose to pluck it out. rather than take a chance on breaking the bulb when reinstalling, i installed it using a section of fuel line as a "grabber".

now is a good time to clean the lens, and speedo face but be carefull of the needle.

i suppose it took, maybe 45 minutes? counting multiple trips to get the right tools. : )

good luck,
bob p

ps. on each bulb, i spread the little wire contacts a bit so the bulb would have a less tendancy to loosen. i tested/wiggled all five and they stayed lit, so i should be good for awhile.

 

Wow, you '79 guys are right and you just sit in the driver's seat? That easy. Man, I learned something again! I looked at Google images for that year. Yep. The early - mid C3's are an exercise in BDSM as far as anything under the dash goes. Agreed, pull the wheel for the older cars.

If you decide to leave the column in, unscrew the turn signal and tilt wheel levers out of the column. It will save you some choice words later on. Why you can remove them lying down on the carpet and put them in the ash tray.

 

a few months ago i had to change the tach circuit board so i did some research here and got REALLY NERVOUS! apparently it involves dropping the steering wheel, pulling the dash, disconnecting the tweedle valve, etc. turns out there was a nice change in 79: just remove the clear plastic lens, remove 4 allens holding the tach in a pull it out. no drama. omg, i was a happy camper.