64 Wildcat Dash Lights

[samdotcom]

Here's a question for the electrical wizards out there. I'm having trouble with the dash lights dimming. The dimming effect only seems to get to "half bright" and then stays at that level.
I have tried the following things to no avail.
1. made sure all the fuses are correct and working
2. made sure both engine grounds are good at the firewall
3. removed 4 bulbs from the dash and ran direct current to them to make sure they weren't just "wearing out" (they were fine)
4. replaced the headlight switch with two different good switches.
Now the strange part about this problem is the fact that all other applicable lights dim and go "bright" when the rheostat turns. (such as the heater control lights and the console tach light. I figured I'd check with you guys to see if I've missed anything before I start to remove the instrument cluster.
I'm out of ideas so far.
The car description is as follows:
1964 Buick, Wildcat, Convertible
no a/c, 401 nailhead, with alternator, and automatic transmission
There are no other "electrical accessories" no power windows, door locks, etc. Every other electrical accessory seems to be working
I respect you guys thoughts and ideas and will reply to any and all responses.
Thanks
Sam

[TurboV6]

Some of the 64s had some bad soldering in the circuit boards, which may have detererated or oxidized over time. pull the dash face and check the board, it may not be allowing electricity to flow correctly

[Special_Deluxe]

Are the dash lights uniformly "dim" or are there splotches of lighter areas and darker areas? How many bulbs are there in total?

If the problem is uniform I'd suspect a ground problem with the cluster harness under the dash, or a supply problem at the plug. Try tracing the wiring harness that goes to the dash- if there's a ground connection under there it might be a simple matter of cleaning it off. Try wiggling the wire harness a bit whilst a helper watches the dash lights, it might be a bad conncetion that just needs some cleaning off. If you can unplug the wiring harness from the dash try testing the supply wire with one of those extra bulbs: If it's full-on bright maybe the connector is bad, or the ground connection for the cluster is bad as detailed above. If the test bulb is dim it means a power loss in the supply circuit- Apart from checking the wiring for shorts and bare spots I'm not really sure how to go about tracing that, hopefully someone with more electrical know-how than myself can chime in But grounds and connectors and checking for bare wires are always a good place to start.

If the problem is "splotchy" with areas of bright and dim, it may be the cluster circuitry or perhaps bad contact in individual bulb sockets. The sockets can be cleaned but anything else probably means pulling the cluster out

Best of luck and hope this helps.

[samdotcom]

Hello everyone
In answer to your questions I have the following answers so far.
The dash cluster has 7 "illumination" bulbs and all of them operate with the same "brightness" when the headlight dimmer switch is used. This "rheostat brightness" for the illumination lights is only "half bright" when turned to the "full brightness" setting. When these same bulbs are removed from the dash and checked with full voltage, they go to maximum "brightness". Therefore I am assuming that the bulbs and sockets are ok.
All other circuitry seems to go to "full brightness" when the rheostat is used. Therefore I again assumed that the headlight switch is functional and possibly that the rheostat is operating correctly.
This is what I'm contemplating doing, before I take out the guage panel. Tell me what you think.............
Since I'm assuming that the headlight switch and rheostat are functional and all the other lights are working correctly, I'm going to replace all the "illumination" bulbs back into the gauge panel and try to get a multimeter to make contact with the circuit board "ilumination" solder lines. Then see if i can read any voltage changes while moving the rheostat in both directions.
Am I correct to believe that the voltage readings should drop on "low brightness" and resume to 12 volts on "bright"? I would try testing the rheostat voltages but it seems to be working for all other components in the dash and associated lights on the rest of the dash.
To be honest, I've never removed the dash gauge set, and even after reading the manual, I'm still just a little afraid to try it. But I will if I have to....(smile) No body likes a coward. (smile)
Well as promised this is my latest attempt to find some answers. I'll try to answer any and all other ideas, questions, or points of view, as soon as possible. Thanks again guys.
Still trying to avoid a dash removal.............................

Sam

[Special_Deluxe]

Hello everyone
In answer to your questions I have the following answers so far.
The dash cluster has 7 "illumination" bulbs and all of them operate with the same "brightness" when the headlight dimmer switch is used. This "rheostat brightness" for the illumination lights is only "half bright" when turned to the "full brightness" setting. When these same bulbs are removed from the dash and checked with full voltage, they go to maximum "brightness". Therefore I am assuming that the bulbs and sockets are ok.
All other circuitry seems to go to "full brightness" when the rheostat is used. Therefore I again assumed that the headlight switch is functional and possibly that the rheostat is operating correctly.
This is what I'm contemplating doing, before I take out the guage panel. Tell me what you think.............
Since I'm assuming that the headlight switch and rheostat are functional and all the other lights are working correctly, I'm going to replace all the "illumination" bulbs back into the gauge panel and try to get a multimeter to make contact with the circuit board "ilumination" solder lines. Then see if i can read any voltage changes while moving the rheostat in both directions.
Am I correct to believe that the voltage readings should drop on "low brightness" and resume to 12 volts on "bright"? I would try testing the rheostat voltages but it seems to be working for all other components in the dash and associated lights on the rest of the dash.
To be honest, I've never removed the dash gauge set, and even after reading the manual, I'm still just a little afraid to try it. But I will if I have to....(smile) No body likes a coward. (smile)
Well as promised this is my latest attempt to find some answers. I'll try to answer any and all other ideas, questions, or points of view, as soon as possible. Thanks again guys.
Still trying to avoid a dash removal.............................

Sam

Based on this information, if I was a betting man I'd put my money on a bad ground in the intrument cluster wiring harness or else a bad connector where it goes into the cluster. Given that the supply line is common for all three componants (heater panel, tach, cluster) but each use a different ground, and a different plug, it's possible that one of these two could cause the problem. These can probably be checked by doing the old "under dash limbo" which is a pain but a whole lot less of a pain than takiing the cluster out!

Please note that I claim no electrical expertise and it could very well be something else but thats what I would check forst.

Best of luck and keep us posted!

[samdotcom]

Thanks Mike...
I think I'll try finding a ground problem cause I really don't know how, nor do I really want to remove the dash panel gauges. (even though I've got the manual). I'll start on it after this weekend due to a death in the family, but I promise I'll keep you posted a soon as I tear into it again.
Thanks Again Everyone..........
Sam

[kimb82]

Interested in what you have found out!
My lights in my 64 do not work at all, the only one that works is the center console light!
Gonna have to tear it apart to diagnose.

[WildKitty]

Ive got the dashes outta both my 64s - gawd that was hard with a bad back
I think I would try some electronic spray cleaner on the lamp switch reostat before I pulled the whole dash - turn the knob as you spray it

Butch

[jamhdit]

I would check the round plug that connects to the gauge cluster it hase bothe the power to the lights and the ground in it.. You can disconnect it and check your voltages there then if they are good it would be in the circit bourd sheet on the back of the gauges