Charging system going bad???

[elevenssc]

Driving my 340 4-speed 1970 Plymouth Barracuda home last week I noticed that my volt meter was pegged on "C".  The wiring on the car is coming up on 40 years old.  Dad did put the "orange ignition box" on the car about 20 years ago.  I didn't think my battery was bad so I've done some investigation and need some help diagnosing/determining next steps.

When the engine is at idle (800 rpm) the volt meter needle is where it should be...right in the middle between "D" and "C".  I put my digital multimeter on the battery posts and it read 11.6V (Shouldn't it be higher?)

At 1500 rpm, the needle is burried on "C" and voltage at the battery is 12.38.  At 2000 rpm, the needle is still burried on "C" and the voltage is 12.5.  I didn't check alternator output yet cuz by this time, the engine was too hot to be putting my hand anywhere near the alternator, and time was running out.

I cut my high performance teeth on my 1979 351 powered Mercury Capri.  If I remember right, voltage at the battery while the car is running was about 15V.  I know the 70's vintage Mopar wiring was marginal when new, but I'd like some help diagnosing what to check next.

PS, I've also noticed that my instrument lighting at night is also getting dimmer and dimmer.

[Chryco Psycho]

My bet is alternator is bad , I would pull it out take ity to a local parts store & test it

[Supercuda]

The bad/dirty connection issue could be rearing its ugly little head, too. Check the connection at the fuse link, and at the battery and starter relay. Also check the ground connections. Age is never kind to automotive components, so I am sure that you will find the problem, with a little close inspection. And, as Chryco said, check the alternator (and regulator!).

[elevenssc]

Thanks for the input.  I'll definately check all connections and get the alternator checked out.

I've been toying with the idea of re-wiring the car since I got it last year.  The reverse lights dont work cuz the wire broke off the connector.  The soon to be 40 year old wiring is showing it's age.  This charging thing only reinforces my feelings that the electrical system needs some TLC.

I've priced the OEM style harnesses at Year One.  For what they want for a complete set of harnesses for the car, I can buy an 18 circuit painless harness, and a second one as a spare, and still have $$$ left over.  Has anyone out there rewired their E-body with either option? (OE Replacement vs Painless)  Anything you would do differently?  Comments and suggestions welcome...

(my car is not numbers matching...originally a 318 3-spd car, now has a 340 4-spd.  The pailness harness would allow room for "additions")

[resq302]

Just my  on this but I used a Painless wiring kit when I built a CJ 7 with a fiberglass Hummer like body on it.  Rewired everything and it was a pain as the kit came with no ends on it and had to cut, route, and attach all of the ends to everything.  I basically had to cut the old connectors off and then solder them onto the new harness.  For the extra money, the OE wiring that Evans wiring does is a simple plug and play type of deal.  Plus you also retain the correct wiring colors in the event that you have a problem, you can still go to the factory service manual and look up the wiring.  But again, thats just my opinion.

[rallyechall]

You may also want to check with Evans wiring.

http://evanswiring.tripod.com/

[ntstlgl1970]

I agree with CP, also the stock alternator doesn't work as well as the one in your capri did, so comparing them won't tell you much.

[RaptorF229]

Ive been doin the year one wiring little by little. The stuff looks great and is pretty much just like the original.

[resq302]

Here's a little secret .......Year One buys their stuff from M&H Wiring.

[FY1 RT SE]

Here's a little secret .......Year One buys their stuff from Evans Wiring.

Wrong!!!

BTW, I would not put an Evans harness in my or anyone I know cars.

[Aussie Challenger]

  Check the voltage at the alternator first, run a wire direct from the + battery and + alternator and check voltage, original Amp guages create high resistance and so does the terminal block on the firewall.   

[resq302]

Wrong!!!

BTW, I would not put an Evans harness in my or anyone I know cars.

Ok, so what is soooooo bad about Evans harness'?

[Chryco Psycho]

I have used Evans with no issues but others have found wires placed incorrectly in the bulkhead plug which I normally check befoe plugging in any new or different harness

[ted]

Here's a little secret .......Year One buys their stuff from Evans Wiring.

not even close

[422STROKER]

M+H makes YO harnesses IIRC and they don't sell it to anyone but YO.

Tom

I had a charging problem the other day, ended up being a loose connection at the alternator.  The main charging wire and one of the field terminals was loose.  I had an intermittent problem figured it was the regulator but was something simple thankfully.  Rock solid now at 14V with the headlights and heat on.LOL  I needed the heat last night coming home.