Really need some help. Years ago when, Texas T Parts first came up with the converted 12V alt, I took the bite and installed same on my 26 This would have been before Ben Hardiman cane on the scene, Last month my brake light switch, (the one that clamps on the bendix can) shorted and before I could crawl into the trunk and disconetc the battery I had a blazing fire going on. All of the wiring looms melted to a chared mess. Well, I've managed to rewire all except the alt. This alt needed to be excited before it would do it's thing. Now, here is my delima, the alt has 2 electrical terminals. One is a cross blade pushon while the other is a threaded stud. Now, which one is the output terminal and obviously the other would be the excite terminal. Anybody out there has any input? And yes, I'm installing a fuse this time.
The one with the nut is the out-put terminal.
It should have about a number 10 wire.
The push-on gets power when you turn the ignition switch on to give Alt. the electricity. It needs to be a # 16 or larger.
I always put a small bulb in that circuit. I am not sure if that needs to be done though, but when I turn my ign. switch on the bulb lights up. When I start the engine and the alt. kicks in that bulb goes out because it is getting electricity from both side.'That way I know for sure my alternator is working. I did not wire in the AMP gage as they often are the problem.
mine is just there for looks.
If it is a 10si the plug should be marked 1-2 or F-R.
2 or R loops back to the the battery terminal. It is a sense wire. It can also be hooked to the battery at the battery to monitor true battery voltage.
#1 or F hooks to the key thru' a diode or light.
It is an output so wiring it directly to key is nor recommended. It you have a distributor it will typically power the coil and you won't be able to turn the ignition off!
That output is only capable for 2-3 amps on a good day and will if exceeded blow the diode trio out.
You could leave it off and just rely on residual magnetism to turn the alt on but it will take a bit of speed but once on will stay on as long as the engine runs, that is what the trio does.
I would use a light (as suggested) or an axial diode on the ignition terminal. It will not work unless #2 is tied to B+.
This all assumes a 10si with built in regulator.
Ideally use a 21/22 SI regulator that heavy trucks use....Then it would be just a battery wire.
Preferably a AC actuated VR for ultra fast turn on speed. The air gap between the rotor and stator can affect that turn on speed btw.
Hope this helps.
Aaron,Mike.....Thanks guy's. Now I have some guidance on how to correctly hook this thing up. You two are a great help....Jerry.
Jerry: get a fuse in there somewhere to prevent having to re-wire a second time!
Aaron, Mike.....What size diode should I use? I have a 35V, 75A.....Is this large enough? And yes Charlie...I have a 20A fuse going in. Don't need to repete this excerise again.
Just curious what happens when the 20 amp fuse blows due to overcharging? I guess it prevents a fire, but you still lose the alternator with no battery attached.
Doug, Hi and a good point. I am planning on puting the 20A fuse in the light circuit which was the cause of my original calamity. I am planning on leaving the charging circuit as/is. My only question is a 75A diode large enough to keep the battery from backing up into the alt and running my day.
Bear in mind fuses are rated in current. Higher voltage will typically not cause a fuse to blow and most alternators employ secondary voltage features. Voltage goes up and the current does not follow.
Your diode idea is an aircraft application. 75 amp is large enough on a 10SI but why do it? If the alternator is not seeing the battery it will have a difficult time turning on and will have to be excited or you will have to rely on speed.
The battery will not "back up" into the alternator unless it has a rectifier issue and at that it will typically be the rotor draw (3-5A) that it will see...Use a fuseable link if you have concerns. For years alts were hard wired into the battery.
The kiss method is the best imho.
I would make sure my loads are as close to the battery as possible. If the alt output goes open and it goes to 28v you'll want your loads not on that line...i.e wire the alt on a dedicated line.
BTW should your diode fail or link the alternator will go into secondary voltage and the stator will burn.
Overcharging due to the alternator is rare. The sense wire can contribute to it and keep in mind the regulators are temp compensated.
Mike, for reasond beyond my understanding I cannot contact you direct using the forum. Could I have your # so I can call you or my address is firstname.lastname@example.org if we could do it that way. 281-451-9949...Cell....Jerry.
On the way..