Classics Roll On By Eli Melnick Spring is my favorite time of year. The onset of nice weather brings out the “summer” cars, the convertibles, the antiques, and a lot of 50s and 60s classics. One such fine example is the early Ford Mustang. Its charging system is avery simple one, yet because it uti- lizes an ammeter rather than a warning light, the wiring confuses technicians and results in unnecessary warranty returns. Most of us are used to the four- wire hookup of the typical Ford ex- ternal voltage regulator. It uses a “‘sta- tor” feed from the alternator to the “S” terminal of the regulator to turn the voltage regulator on and turn the ALT warning light off. The warning light is controlled by a green/red wire, which connects to the “T’ terminal of the regu- lator. When the car comes equipped with a gauges package, an ammeter is used to monitor the charging system rather than a warning light. The green/red wire becomes an ignition feed wire that is energized by the ignition key. However, it is not hooked up to the “T’ terminal as one might assume but instead, it is used to turn the voltage regulator on via the “S” terminal. This makes the stator feed from the alternator unnec- essary and that’s when problems be- gin. The alternator itselfhas three con- nections. One, of course, is the main BATTERY terminal. The second is the FIELD connec- tion. The third wire in this application is a GROUND lead. For some rea- son, a lot of installers insist on con- necting this ground lead to the insu- lated STATOR terminal. This shorts out the rectifier, damaging an otherwise good part. Whenever we get called for help on this type of system, we try to get the vehicle into our bays—tt is much easier to correct hands-on than trying to explain the system over the tele- phone. Since these vehicles are over 30 years old, most of them have had the voltage regulator connector replaced. The new universal connector comes with six wires in four terminals, an over- kill for these applications—where three wires and three terminals are all that is required. We have found plenty of combinations of wrong hookups so get your side-cutters out and “cut” the confusion… One word of caution. On some early 80s Ford vehicles with the op- tional gauges package, the STATOR output from the alternator is used to feed the electric choke heater, but has nothing to do with the voltage regula- tor. Remember that the choke heater voltage is around seven volts when checked with a DC voltmeter. Isn’t it nice to see these classics run the way they were designed? Overcharged Duster As the summer rolls in, so do the old classics with their own unique problems. This time it is an early 70s, delightful Dodge Duster with an over- charged battery complaint. Its proud owner had taken it to several garages that kept replacing the alternator and/ or the voltage regulator. This didn’t solve the problem, and in the process his wallet was overcharged as well. This scenario arises from Chrysler’s design of the charging system, which has always used an externally-regu- lated alternator. Starting in 1970, JUNE/JULY, 2000 Chrysler implemented an electronic regulator mounted on the firewall or the inner fender. It had a triangular two- terminal plug. One of the terminals was connected to the green field lead (‘A’ circuit) while the second terminal was fed from the ignition switch via a blue wire, which served as the SENSE ter- minal. Using an ignition feed for voltage sensing is not a good idea. Since it car- ries quite a bit of power for such loads as the alternator field, choke heater and the ignition coil, this circuit can exhibit substantial voltage drops—as much as two volts! You can fill in the rest of the story. The voltage regulator is factory-set at 14.5V, so with the voltage-drop added, we end up with a battery charg- ing voltage of over 16 volts. There is an easy cure that we have been using for years with great suc- cess. We add a Bosch-type relay to the circuit. We cut the ignition-feed off the regulator plug and use it to ener- gize the relay. We then connect one of the normally-open contacts to the posi- tive battery cable (actually at the starter relay) and the other contact to the SENSE (blue wire) terminal on the regulator. Whenever the ignition switch is turned on, the relay is energized and the SENSE terminal of the regulator sees the actual battery voltage. Make sure that you solder the connections, possibly even using a fusible link to protect the installation. After all, an overcharging classic is better than a burnt-up one. Eli Melnick is owner of Start Auto Electric, Ltd., Toronto, Ontario. Questions? Write Eli at Melnick@home.com Page 1 of 1