flickering lights

[76 cadillac bob]

Greetings fellow restorers,
Have a 1976 Eldo Conv 80,000miles  and am almost restored. New everything including an alternator, however, first time driven at night last night   lights dim and flicker a bit and when I move power seats everything dims badly. Just had a major tune up. Battery installed 2014 by prior owner. Everything works well otherwise. It has to go back to mechanic as replacement wiper motor only works if you slap it hard
LOL I got mad and it worked!! This is one twisted car.....any suggestions on the dimming issue?

[30326]

Re-check the grounding wires. Usually the fault 9 times out of 10.

[Scot Minesinger]

The connections at the alternator caused this same problem for me, it was easy to fix - check that too.

[bcroe]

Have a 1976 Eldo Conv 80,000miles  and am almost restored. New everything including an alternator, however, first time driven at night last night   lights dim and flicker a bit and when I move power seats everything dims badly. Just had a major tune up. Battery installed 2014 by prior owner.

I guess "everything" means a new timing chain? 
Certainly there is a voltage droop at the lights.  If reving the engine a
bit bring the lights and voltage back up, it means either the battery has
developed enough internal resistance (or poor termination) to cause excess voltage loss at high load, or the alternator is weakened and
can't put out much power at idle. 

If not these, there is certainly excess resistance in the wiring, either
in the 12V or ground path (or both).  I'd throw on a heavy load in
addition to the lights (blower, rear defog) to make the lights dim. 
Measure the voltage drop between the 12V battery to the alternator
output post, and to the + terminal on the light.  Voltage should on
the order of 0.3V or less between them.  Same on the bat ground,
alt case, and light ground terminal.  This voltage should be 0.1V or
less.  If you detect the problem, walk one meter probe down that
wiring to find the spot where the big loss occurs.  Bruce Roe

[TJ Hopland]

New alternator?  New or rebuilt?   Typical parts store unit?   Or specialty vendor?   Either way I would take it out and have it tested.   Lots of poor quality stuff out there these days.    Checking connections is good but won't help if the alternator can only put out 1/4 what it should. 

Did 76 still have the connector in the starter harness?   If so that is also a good place to look for issues.  If its there its a 6 pin connector about 1 foot from the starter.   73 had it and it was gone by 78. 

[fishnjim]

If you can't diagnose electrical, take it to a local auto electric shop.   

I think by '76, the voltage regulator (VR) was in the alternator.   That controls the voltage and should not allow voltage to drop such that the lights dim when large draw like power seats.   That's a classic sign it's not functioning properly and/or a weak battery.   If the VR is not working, it'll run down the battery, so you have to check both.
The flickering can be either a loose wire, bulb, or a bad battery cell.   Always best to just go ahead and get a new battery and cables.  Test the alternator after installation.   Make sure the proper wire gauge and CCA size.   Some use smaller than is required to "save" a few bucks.

[76 cadillac bob]

thank you all, I believe battery and ground could be the issue, I always go with simplist and cheapest first, then work my way through.