Raising Alternator Voltage
Posted: Tue Mar 02, 2010 7:49 pm
I am currently running a Lucas a133 (ex Ford Fiesta) alternator from a scrappy in my early +2. The voltage regulator ran at 14.1V on no load (just the engine running) measured at the starter solenoid, and fell to 13.5V with the lights and ventilation fan on. Regulating quite nicely and with plenty of alternator power in reserve.
The trouble was, I could have done with a higher regulated voltage, as that voltage is at the highest part of the system, and voltages at the lights were just about 12V, and at the cooling fan 11.5V. I would call my wiring adequate, and pretty representative of a standard setup. And we all know about that volt drop from the engine to the battery miles away in the boot.
So I looked into it (some of you may already know about this of course), and there is a way of raising the alternator voltage.
You have to extract the alternator, and open it up. What you are looking for is the voltage regulator, which may be a separate module, or a clearly defined circuit on its own. You have to refer to a diagram of the alternator to be sure, of course. The earth wire from the regulator to the "chassis" or metalwork of the alternator now needs to be identified. If you can't find it go no further, otherwise you need to cut this wire and wire in a power diode to the cut ends, with the cathode (identified by a white line) connected to the "chassis" end.
I used a 600W diode with a forward current of 3A max and a reverse voltage of 200V. Anything similar will do.
The alternator voltage has now been raised by 0.6V, so everything seems to run like a car with a battery in the engine compartment, with a corresponding 0.6V uplift .
I will trial it over the next few weeks, and see what effect it has on the electrics. Bulb life will be shortened a bit, but hopefully I wont find out for some time..... The cooling fan will also blow harder
NOTE THAT THIS IS NOT A CURE FOR FAULTY WIRING AND EXCESSIVE VOLT DROPS IN THE SYSTEM. PLEASE MAKE SURE YOUR SYSTEM CONNECTIONS AND WIRES ARE OK BEFORE CONTEMPLATING THIS.
Good luck to anyone who wants to try.
Dave Chapman
The trouble was, I could have done with a higher regulated voltage, as that voltage is at the highest part of the system, and voltages at the lights were just about 12V, and at the cooling fan 11.5V. I would call my wiring adequate, and pretty representative of a standard setup. And we all know about that volt drop from the engine to the battery miles away in the boot.
So I looked into it (some of you may already know about this of course), and there is a way of raising the alternator voltage.
You have to extract the alternator, and open it up. What you are looking for is the voltage regulator, which may be a separate module, or a clearly defined circuit on its own. You have to refer to a diagram of the alternator to be sure, of course. The earth wire from the regulator to the "chassis" or metalwork of the alternator now needs to be identified. If you can't find it go no further, otherwise you need to cut this wire and wire in a power diode to the cut ends, with the cathode (identified by a white line) connected to the "chassis" end.
I used a 600W diode with a forward current of 3A max and a reverse voltage of 200V. Anything similar will do.
The alternator voltage has now been raised by 0.6V, so everything seems to run like a car with a battery in the engine compartment, with a corresponding 0.6V uplift .
I will trial it over the next few weeks, and see what effect it has on the electrics. Bulb life will be shortened a bit, but hopefully I wont find out for some time..... The cooling fan will also blow harder
NOTE THAT THIS IS NOT A CURE FOR FAULTY WIRING AND EXCESSIVE VOLT DROPS IN THE SYSTEM. PLEASE MAKE SURE YOUR SYSTEM CONNECTIONS AND WIRES ARE OK BEFORE CONTEMPLATING THIS.
Good luck to anyone who wants to try.
Dave Chapman