Can someone explain the 70s charging system for c bodies only classic mopar forum electricity billy elliot lyrics


I dont wanna chase my tail here thats why I am asking. I am starting the car, see the 14.7V. Sometimes putting load (Fan, headlights) on it it stays like that, then…fairly unexplained and suddenly I see 12.5V… sometimes 13v sometimes 13.8 (that does not change when i rev the engine) sometimes lower but thats a gauge calibration issue. When this happens and the e-fan is on, I can hear how it slows down. It then can also happen, that the Voltage goes back up after a while!?

It is a dual field Powermaster 95amp alternator (puts out 60something at idle). With an adjustable 70s style voltage regulator. Its connected via relay from the battery to a junction for IGN+ with a bunch of other stuff. Does the voltage regulator somehow sense anything, even with load on it which makes it stop/reducing putting out? The charge battery output wire runs from the alternator stud through a big fuse and then to the batt+ terminal. on the batt side of the fuse is where i also get battery power for accessories that require it!

The factory wiring cannot handle that amperage and you risk a fire or a meltdown under your dash. You don’t tell us the year, make and model of your car but a 1970 C Body likely did not have more than a 50 amp alternator unless it was a police car with heavy duty Leece-Neville alternator and associated components and you are potentially putting amperage through the cars wiring that is twice what it was designed to handle.

The factory charging circuit runs through the volt or ammeter gauge in the dash before it charges the battery and the wiring to the gauge and the gauge itself were not designed to handle that much amperage. You need to do a volt/amp gauge bypass IMHO. Google MOPAR volt or amp gauge bypass or search for it on or on this site.

The short answer to your question is that a voltage regulator, if working properly, regulates the voltage depending on the draw. When you first start a car the voltage regulator can put out 14 – 14.5 volts to charge the battery and then it will lower the voltage accordingly to maintain the battery at a full charge and will vary with the load on the battery. Keep in mind that a 12 volt system is really not a 12 volt system. A fully charged battery should show 13.8 volts. Always check the voltage at the battery. Please read the above reference materials and tell us everything about your car and any alterations/changes to the charging system.

Question FOUR, why the perceived need for an adjustable voltage regulator, although Chrysler sold some back then, but NOT as OEM factory equipment. They were usually used on vehicles which saw many short trips that didn’t allow the battery to get fully-charged on each trip.

Be advised, too, that consistently running too much voltage in the system will compromise the durability of EVERY electrical item in the car, including light bulbs, as the Direct Connection Race Manual states. One reason to NOT use the DirectConnection voltage regulator on anything but a race vehicle with electronic ignition. I found that out myself!

The alternator does not know how much load it’s producing or why, as that’s a function of the alternator’s design output and engine rpm. The regulator modulates that output to best fit the needs of the vehicle’s electrical system (at a particular point in time). The mechanical regulators had "points" which performed that function. The FSM details how much output is allowed at particular ambient air temperatures surrounding the regulator.

GM went to a "voltmeter" in the earlier ’70s on their then-new models (Camaro/Firebird, for example). It was claimed that this gave a better look at the health of the electrical system than an "Ammeter" with a needle that swung back and forth as to how much load/charge was being used/produced. One the newer vehicles, the charging is controlled by a computer module (as Chrysler’s been doing for a good while). The "normal" range goes from about 12.6 volts to about 15 volts . . . and the needle can be anywhere in that range at any time. Usually more when first started and drops to the lower levels the more the vehicle is run. It’s temperature-variable, too. One of those "As long as it’s in the range, all is well" things.