my 69 roadrunner idles at positive charge but when i go down the road when the rpm raises the car discharges below mid point until i shift to a diff gear then i goes up to poss again then when i get to the top of the gear it happens again is this normal ?? plz help thanks in advance

 

Are you sure the wires on the ammeter are not connected backwards? That's the first thing I'd check.

It would be relatively normal to show a slight discharge at idle. Especially if you have accessories or added goodies drawing power. A significant discharge means you have things hooked up to the battery side of the system instead of the alternator side.

These cars were designed around the alternator powering everything, except starting the car. So everything hooked up to the battery side would actually show as a discharge on the gauge.

 

well im not sure about connection but it seems worst at night with the lights on which is normal i would think with the lights and the extra draw how do i tell if there not correctly connected ? is there a easy way to tell or could it be the alternator it looks pretty new and it says re-manufactured any help with a diagram or a pic would be really helpful thanks

 

Check and clean the Regulator to make sure it has a good ground up on the firewall. Also make sure you have a good ground from the engine to the body.

 

As Carnutt said........do THIS

Get in, everything OFF engine not running, and turn the headlights on

If the ammeter is hooked up correctly it will go to the LEFT to discharge

CHECK THE belt tension. Very very common for a belt to be glazed, worn, loose, or even wet for a time after splashing through a big puddle, and the thing will charge at low RPM, but the belt slips at higher RPM.

You still have a factory style system, that is, the older 69 / earlier regulator which looks sorta like this?

http://vintagemoparts.com/img/p/440-1620-thickbox.jpg

If that is what you have, try this test. At the alternator, remove the green field wire, that is, the small "push on" connnector. Hook a clip lead to that terminal, and clip the other end to the big alternator output stud. Start the engine

It should charge just off idle, and when speeded up should really lay over. IT IS BEST to monitor battery voltage with your multimeter ........which I KNOW you have......... to make sure battery voltage does not go too high, IE over 16V

Turn on lights, heater, other loads, and "replicate" cruising RPM. The ammeter needle should be able to keep up if the battery is charged.

If not, and IF you have checked the belt, you probably have an alternator going south. Bad / sticky brushes, or other internal problems

 

Great, fast & easy test.


The wiring (if original) should be connected with black on passenger side stud, this is the alternator side of the circuit (comes from the alternator). Red should be on the driver's side stud, this is the battery side (goes to the battery).

FYI: All loads / add-on's should be mounted on the black wire (alternator) side of the gauge, whether under the dash or under the hood. So any add-on's or even repairs, should all be on the Black, passenger side stud of the gauge. Unless some one added an upgraded wire for the battery charging circuit.

Unlike vehicles today, these cars were designed around the alternator providing all the power, other than starting the engine.