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Old 12-15-2011, 09:55 PM   #1
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Default 78 Dash Lights

i need some help with dash lights. I do not have dash lights for my speedometer or tach. the hi beam indicator is on with low beam and off with hi beams. The both turn signal indicators stay on when headlight switch is turn on. with the headlight switch on the headlights flicker, the tach stops working and the car wants to die. with headlights off the car runs fine. I have dash lights to the gauges. Do i have a bad headlight switch?
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Old 12-15-2011, 10:19 PM   #2
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What is your alternator voltage output?
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Old 12-15-2011, 11:08 PM   #3
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is this something that just started happening or are you in the midst of any work on the car by chance? i agree it sounds like your alternator (probably the regulator built in) isn't functioning properly. if i remember correctly, the internal regulator can be rebuilt without rplacing the whole alternator.
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Old 12-17-2011, 10:11 PM   #4
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i just finished the interior of the car...new seats, carpet, radio. voltage checks out on alternator.
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Old 02-16-2012, 06:03 PM   #5
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Wow, I have a '78 with nearly the exact same issues.
The headlights work ok, and the engine does not act like it is going to die though.
If I dim the gauge lights until they are off, all the gauges work fine. just no lights. If I turn the dimmer switch the center gauge lights work but the blinker and high beam indicators do as you describe. Tach stops working too.
My thought was a new switch too. Were you able to fix yours?
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Old 02-16-2012, 08:00 PM   #6
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Originally Posted by m and t's77 View Post
What is your alternator voltage output?
Would this be relevant if the engine was not running?
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Old 02-29-2012, 11:34 PM   #7
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To the op.
I hate to say it, but double check the wire harness that plugs into the back of the instrument cluster. I did not make note of mine when I disassembled it tonight, so I cannot say for sure that it was plugged in backwards. However, I checked all of the connections with a test light verify that they were good. They were. When I reassembled the dash I noticed that the plug could be plugged in either way. There is definitely a right and wrong way. I made sure it was plugged in correctly and surprise. Everything works perfectly.
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Old 03-01-2012, 10:38 AM   #8
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I'm sory to keep going on about this. I was sure there was some major malfunction that I would never be ably to fix. I'm very relieved it was something simple. Looking at the wires you could imagine how goofed up it would be if the harness was plugged in upside down. It's amazing anything worked.
Click the image to open in full size.
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Old 05-06-2013, 12:00 AM   #9
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My 78 is having a slightly different issue-

The speedometer and tach work fine, other than a 3-8mph speed discrepancy... But the back lighting, and the signal/high beam/warning lights all don't work. The center cluster lights all work if anyone is wondering.

I had the cluster out today and found out that 3 of the bulbs and holders are missing, and 2 more bulbs are also missing, but the holders are there. I cleaned up all of the connections and the contact area of the printed circuit while the cluster was out...

Are the missing bulbs making a break in the overall gauge lighting circuit? Or is some other issue going on?

I swear that the high beam indicator worked last summer,but maybe not...

I'll have to look at the fuse tomorrow to be sure the circuit is getting power, but they all were fine the last time I checked.

Any help would be great- Thanks
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Old 05-06-2013, 12:00 AM
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