How do voltage regulators work?

[Jonnyswboy]

I have a 2010 Mazda 6 with a stock alt and it charges around 13.6v. I am going to get a Singer 390A and am wondering if it will still charge at the same voltage as with the stock alt. What regulator would work with the singer alt if I needed one?

Thanks.

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[Buck 5,000+ posts]

The alt charging is determined by the FIELD wire. If you don't have an external voltage regulator, then you almost certainly have one built into the alt itself. Usually the car computer determines charging voltage, unless you have a regulator where you can choose the actual charging voltage.

So usually you have to have the alt built to be prepared to use an external voltage regulator, I believe. Correct me if I'm wrong, but ext volt reg alts vs just plug and play alts have some different internal parts.

 

[Buck 5,000+ posts]

On my 2003 Explorer, that body style was notorious for low voltage charging from factory. I had 3 alts, the factory one, the a re-made factory one at 180 amps, then my 300 ext vol regulated alt. My car computer would be lucky to chage at 14v. A lot of times it would fall to 13.5-13.8v, iirc. The rebuilt factory HO alt helped, but it would still not charge that high. I would charge at 14.8v-15v with my 300 amp ext vol reg alt. They can be a pain, the regulators.

Your alt will still put out power, just having the car computer control the voltage, it may very well affect or lower the charging voltage of your new alt. You'll just have to see. As long as the alt is charging under a load, I wouldn't worry about it too terribly much, unless you want it exactly how you want it.

 

[Slo_Ride 5,000+ posts]

Most alts these days are internally regulated. Most modern cars don't use a regulator at all, it's controlled by the ecu

 

[metalheadjoe 10+ year member]

The alt charging is determined by the FIELD wire. If you don't have an external voltage regulator, then you almost certainly have one built into the alt itself. Usually the car computer determines charging voltage, unless you have a regulator where you can choose the actual charging voltage.

I don't think this is correct. I thought the field wire basically makes the alternator start charging when it sees the engine running. Otherwise self-exciting regulators wouldn't work. I'm not sure, just speculating here.

I can tell you that the computer in my pickup doesn't have any parameters to change the charging voltage, though that is a lot older.

 

[Buck 5,000+ posts]

I don't think this is correct. I thought the field wire basically makes the alternator start charging when it sees the engine running. Otherwise self-exciting regulators wouldn't work. I'm not sure, just speculating here.

I can tell you that the computer in my pickup doesn't have any parameters to change the charging voltage, though that is a lot older.

I think it can be designed several different ways. I know my FIELD wire changed the voltage that my alt charged at, because I measured the FIELD wire voltage while changing the charging voltage, and they went up and down together. I think the FIELD wire is used to let the alternator know the load on the electrical system, maybe in a more advanced way. The FIELD wire was literally the only wire my alt had from the voltage regulator. The only other wires on the alt were the power and ground wires for the alt power output. The FIELD wire from the regulator was literally the only wire that interacted with my alt, my main FIELD wire from the car computer was left unhooked.

 

[Slo_Ride 5,000+ posts]

Field was said so many times in that post it made me think of the movie line, "What's a field car". Lol. I love that movie.