Hi, I just joined in hopes this group is better than others. I took my dash out and when I put the Tac/ Speed cluster back in one side of dash lights are brighter than the other. I messed with ground and didn't seam to make a difference. Both set of bulbs have been changed at the same time. they don't flicker, they work as they should except for the brightness All bulbs appear working and both sides are even just one side is brighter. Please help!!
1972 Vette 350ci
Thanks
Jerry

 

Firstly, WELCOME!
Was this issue there before the work you did? If not, your work changed something. But if that issue also existed prior to your work… Have you attempted to clean the points of contact that the bulbs make in their little sockets? With something like NO-OX-ID?
Most of these old ‘Vette’s guage backsides exhibit corrosion on the housing. A sure sign that over the years moisture has been there. If it has been on the back of the housings, you can bet some has made it’s way down to those little sockets. If you pull those bulbs and clean the contact points you may see an improvement. Not a bullet prooof, no fail solution, but may very well be the ticket. Hope this helps!
What happened at the other groups? Sounds like that may have been a not so positive experience. Lot’s of positive, helpful folks here, but we still get the occasional snarky type as well.

 

I know there's no room behind the speedo/tach to do much of this but...

The dash bulbs get their grounds through the housings they click into. This means that not only do the bulb's contacts in the sockets need to be clean but the housings' prongs and gauge holes need to be clean too. Scuffing the prongs and holes with 320g paper would be a good measure, plus, after inserting the socket in a gauge hole rotate it back and forth a couple times.

 

If the bulbs came from the same package (I assume you changed them all), then I still believe you have a faulty ground. It could be a weak joint where the wire fits into the connector, a poor connection (too much paint in the wrong place?), metal corrosion, whatever. 12vdc power comes from the same source for all the lights, so that's not your problem. If all the lamps on one side of the pad are the same brightness, but one side is dimmer than the other, it [almost] has to be a grounding issue.

 

I would like to Welcome you to The Corvette Forum Painter1982! This is the best place to go when you have some really tough issues to so solve regarding a C3.

My first guess would be that you are experiencing some sort of compromised ground in that circuit.

Is it possible that the bulb that is brighter, or might be brighter for a reason, like a seat belt light or some other application?
This sounds dumb but the wiring harness on the bulbs under my 57 year old dashboard is so long and could easily be used in the wrong place. I would be looking at a wiring diagram for the 1972 Corvette and see what things look like. There might be sockets rated for a higher wattage but still using the 12 volt standard. Maybe a stereo bulb of one used in a seat belt light. So a lower wattage bulb will make slightly less light on the same 12 volt circuit. It sounds like you are dealing with different wattage 12 volt bulbs. They are probably for different circuits that might require the extra brightness of the bulb for some reason.

Imagine, like in a home, you have 120 Volt AC service and you can choose what wattage you would like. A higher wattage is going to be brighter but use more power. A Lower wattage bulb produces a lower level light output and we are happy while saving money. In a car, we just don't get to choose.

For cleaning the connections in your C3 I like to use a material called DeOxIt. This stuff really works. Thanks to our buddy litevette, as he mentioned the back side of the instruments on the earlier C3's have had a lot of corrosion issues. As I mentioned earlier, my C3 is 57+ years old and most of the original light sockets, switches and connections have had some corrosion on them. The DeOxIt worked wonders removing the old grime from 57 plus years of abuse in the auto world. While working on my car one night I did a side by side comparison and I would not have believed it had I not seen it in front of me what a difference in light the clean sockets could make. It made a big difference and 99% of it was getting a better ground with a good solid cleaning. The DeOxIt is a chemical based copper/ brass cleaner and removes they claim 100% of the corrosion.

IF there was there was No DeOxIt available then I would suggest using a #2 Pencil's eraser because it is soft rubber with a superfine grit. I have pulled off the road and polished the brushes to get certain engines to charge in the old days. The Pencil is probably the best and safest way of cleaning any small sensitive device.

Whatever you do, Whatever you add, Just Please don't put any Die-Electric grease in or on the bulbs or their sockets. Die Electric Grease is for the spark plug wire end-cap that get stuck on the porcelain tops of the spark plugs. It BLOCKS electricity and will mess your electrical system up.

Battery Grease IS Conductive and is made for keeping connections free of corrosion by blocking air from getting into the connection. I have installed thousands of 2 volt battery cells that held about 5.5 gallons each of electrolyte per cell and am used to cleaning the surfaces and then applying battery grease to them. A common ritual in the warmer climates or those in the Marine Environment. I got to enjoy much of my time out chasing Camels across the deserts between installing new batteries.

You might need to try a new light socket and bulb just to verify what is going on down there.