I went to start my 70 Charger today and at first I thought I had a dead battery since it clicked a little and the dome light was dim. I put the battery charger on it and it looked like the battery wasn't taking much of a charge. I had driven the car a few days ago and it was fine. I checked the voltage at the battery with my multimeter and it is 12.5 volts (with no load). I jumped the starter relay and I got a spark and the stater solenoid clicked a little. I tried turning the key again and got a buzzing from the starer relay then I tried it again and I get nothing. The starter relay won't even click. The dome light still comes on very dim but voltage at the battery is 12.5. I checked voltage across the starter relay and it is 12.5 there too so it should not be a battery connection issue.

How can I have 12.5 volts at the battery and across the starter relay but my dome light be very dim????

Did you try twisting the battery terminals at the battery? Corrosion builds up and can create resistance. Same goes for any other electrical connection related to the starting system. The connections at the starter are less likely to corrode since they often get a thin (or thick) coat of engine oil from leaks!

I did take the connections off and then put them back on. The weird thing is that for the starter relay to get 12.5 volts the cables must be good but I can't figure out how the voltage at the dome and console lights could be reduced. They are very dim, like maybe 6 volts at them. And with 12.5 volts at the starter relay shouldn't I be able to jump the relay and get at least a spark if not get the solenoid to click and or starter to turn? I'm going to borrow another battery and try it but it doesn't seem that would make sense.

Electrical stuff can be tricky. I've heard of guys giving the starter a few taps with a hammer....
Sounds crude but it cant hurt to try.

turn on your headlights and turn the key or jump the relay.

if your lights go out you just don't have enough charge.
it could be a bad battery, as 12.5 is a little low to me.
I normally see 13.2 on a good batt.

it could also be the cables, as I have had ground wires go bad and not let me turn it over at all.
in which case you can try jumping the car with pos to pos , ground to block and to neg on the good running car and see if that helps.

That actually worked for me one time. Battery's have 2.2 volts per cell so you should get a reading of 13.2 volts on a good battery. You could pull the caps and fill the battery cells back up and recharge.

All the + power for EVERYTHING except the big heavy cable to the starter for the starter motor power goes through the firewall bulkhead connector and then through the AMMETER on your gauge cluster before going to everything else in the car including your ignition switch. It is real common for the bulhead connection to get a bad connection and or FRY, and it is even more common for the AMMETER to fail. The Ammeter in these cars is in series with everything so when it develops a problem it affects power to everything.

Follow the positive wire from the battery to the starter relay to the bulkhead through to the other side of bulkhead to the ammeter etc with your voltmeter. Its tough but you can reach up under dash and see what kind of voltage you have at each side of ammeter. I bet somewhere in there you see a sudden large drop in voltage.

You might very well have battery voltage at starter relay untill you put a load to the system. There might be enough continety to make the dome light glow but as soon as you load the system it falls on it' face. Have seen this caused by corroded or lose battery clamps and other bad connections. Check voltage at starter relay also with key in 'start' and 'run' position. Voltage might drop a lot when key is turned. Or even easier: Check battery terminals and ground battery - engine -chassis. Hope you get it sorted out.
Lars

Try another battery that you know to be good. I've had two act like that both times it was the battery.

I feel like a major dummy. Right away I took the cables off and then put them back on, kind of twisting them figuring that would take care of any bad connection. They weren't gunked up with the white powder you get from a leaking battery. I was going to borrow another battery from my dad and he gave me his battery terminal cleaning brush too. I figured I'd try really cleaning the terminals on the battery that was in the car good first and that was it.

I have had another vehicle where the battery terminal connections got gunked up but on that one I tried to start it and it clicked once and then was totally electrically dead. On the Charger there was still some current passing, enough to make the mutimeter measure it but even the load of the dome light was enough to cause the voltage to drop a lot and there wasn't enough voltage to even engage the stater relay or solenoid.

Glad you found the trouble. Cheaper than a new battery too.Wish I had been as lucky.

Glad you fixed it. I was going to say on my 70' ocassionally even though in park it will not start. Push up on the shifter just a little harder & try again it usually will start. Sometimes it is just enough out of park (even though locked in position) to engage the neutral safety switch to keep it from starting. Just a thought.