The Stovebolt Site Forums The Shop Area Engine Shop alternator

my truck is converted to 12v but the alternator is sending 13.5 v to the regulator only. it is hooked to the left side of the regulator. should'nt there be a wire going back to the battery? if you check running voltage at the battery you only get 11.5 and 13.5 at the regulator. which means it really isn't charging. got any ideas?

indianajay,

A system with a externally regulated alternator..your system, should indeed have a large gauge wire from the BATT post on the alternator going to a common connection with the battery somewhere. This is usually on the ammeter, but could be as simple as junction block on the firewall or common connection on the starter.

The regulator might have four terminals, and the alternator should be connected to two of those..the 'F' terminal and the #2 terminal. There should be a 'big fatty' with all the power in it going from the alternator to battery via the ammeter or 'sumpin'.

It has to be there, you just might not see it!

Stuart

Is the alternator internally regulated and single wire? If so, the wire from the alternator goes to the BATT terminal of the regulator and that should go to the battery through the ammeter. The regulator is just along for the ride in that case.

i think my alternator is not internally regulated. it has three post and the diode thing. it looks old. i am used to one wire setups on hotrods. and this is all unfamiliar territory to me. it sounds is if i leave everything the way it is and add a #2 hot back to the cut off switch on the firewall, it should work.

indianajay,

Something is rotten in Nashville. Was this thing working..has it ever worked. Your reading of 11.5 volts is NFG. A discharged 12 volt battery is about 12.5 volts...11.5 volts would be long gone! The 13.5 is goofy too. The alternator should be easily into the 14 + volt range.

The regulator should have four terminals.

Regulator F to alternator F.

Regulator #2 to alternator R.

Regulator #3 to a connection with system voltage..maybe on the starter or the the BATT post of the key switch.. somewhere to sense voltage.

Regulator #4 to key switch. Powered when key is switch ON.

The power wire from the alternator..the BATT wire goes into the system, either through a ammeter or to a connection on the starter. This is its path to the battery.

You haven't indicated what kind of rig you are working on. Keep us posted.


Stuart

my regulator has three terminals. from right to left the terminals say F gen and the last one is too rusty to read. that is where the alternator is hooked up to. it looks like it may say fn or fc i can't tell

indianajay,

Does that last terminal say BATT. Do you have a alternator or a generator . I haven't seen a alternator used in conjunction with a three terminal regulator. :confused:

Stuart

1951 6400 with a 248 gmc motor. I know what your saying like i said i am used to good alternators that have one wire and put out 14+ volts. am thinking i will get one and start over. my truck will discarge down to about 10 volts and still start before it has to get charged with a batt charger. i assume it has a 6 volt starter.

A good alternator with internal regulation will easily put out 13.5 volts. No problem. No internal regulation will get you 16-18 volts. Blow up your battery.

One wire setups are OK for hotrods only run on weekends. It will eventually discharge the battery over a long period of non use. Three wire setup is what you want for a daily driver. You may have to change over your keyed switch to one that will accept the 3 wire setup.

indianajay,

A functioning alternator will always put out at least 14.5 volts. You haven't indicated if this is a new setup you are installing, but it sounds like it is.

If your alternator is externally regulated, it won't work with the regulator you have described.

If your alternator is internally regulated, the old voltage regulator could hang on the firewall as a decoration, but as Baldy pointed out, it wouldn't be used in the system.

The tab configuration for the alternator regulator..the little things where the DA plugs in will indicate which type you have. The case is usually marked R & F for an older external model and 1 & 2 for the SI, or internal styles.

Only one of these units uses a regulator hung on the firewall, and it isn't the regulator you have.

All alternators are good and all will work fine...you just have to know what you have so you can proceed accordingly. One wire units are easy to install and work perfectly for any service.

Stuart

jhaa_lives's statement that a one-wire alternator ". . will eventually discharge the battery over a long period of non use" is information I had not seen or heard before. Is there a link to an explanation for this?

Is a long period 1-month, 3-months, 6-months, 1-year? I have not observed this over a 6-month northeast winter hibernation.

The only problem I'm aware of on the single wire alternator is that the engine has to be revved to ~1200 RPM or higher to get it to charge when you first start the engine, after that, it works just like a three wire and charges at idle. In normal driving, even if you didn't intentionally rev it to get it charging, you would get it charging just going up through the gears. Any alternator can discharge the battery if the diodes leak.

true about reving the motor most of my rods and boats were like that. here is what i have discovered my alternator has an f on it.i will take it too autozone and have them test it. the wiring is wrong. my regulator has three post
batt gen f

the f wire is hooked to the battery the gen is hooked to the alternator post with the diode and there is nothing on F. should i put f on f leave gen where it is and battery side leave alone? I will get the alternator checked and get a new diode too. thanks for your help stuart you are a real help to me. for some reason when people cut into wires and make a mess of things i get alittle intimidated. sometimes it's easier for me to cut all the wires and start over.