12 volt question

[Dale Uhrich]

I have converted my truck to 12 volt and installed a 12v bosch alternator. It requires a brief 12 volt connection to make it start charging that is usually hooked to the starter system when it isn't foot operated. Any idea other than a momentary switch on the dash?

[MBF]

If you're not concerned about originality you could replace the igition switch w one that has a start position and use that just to energize the alt. Depending on how far along with the conversion you are you may be better off going to a GM internally regulated alternator. That's what I used on my 52 1 ton and 36 Plymouth. Mike

[greg g]

Run a wire from the starter post of the solenoid, this will be hot only when the key is in the start position. But you will need a diod in the line to make sure the alt doesn't back feed the circuit. the other option would be to get a Ford type solenoid with the snd small post, this is designed to bypass the resisted line to the coil to allow 12v to the coil during starting. Again this terminal is only energized when the key is in the start position. When the key is released, it is a dead end.

[grey beard]

Unlike MoPar automobiles, Pilothouse trucks have no solenoid. They're "kick" start, if you remember. As mentioned earlier in this thread, GM 10-SI alternators are self-exciting, and need no external line for this purpose. The problem with using them is that they require significant rpm to build up enough field current to energize the circuit - no problem on modern engines but a pain on older trucks and tractors.

If you use an alternator, best to get the correct diameter pulley so the alt turns at proper speeds. Many have used the old gen pulley because of belt width prblems, but these are always too larege in diameter, and affect alternator speed aversely. The diode mentined earlier is necessary to keep current from backfeeding from the alt through the ign switch on shut-down, so the engine doesn't continue to run. (It feeds the coil after the switch is turned off.) LOL

[Dale Uhrich]

would it work to put a diode in the line from the output of the alternator so it can flow toward the battery only. then install a 12 volt relay with a 12volt hot source tied through a closed set of points to the energizing tab on the alternator. next tap the output post on the alternator to the coil on the relay so when it starts to generate it will energize the relay and disconnect the other source from the alternator.

[greg g]

I keep forgetting the trucks have that foot thing. So I guess it you went from the big post on the starter up to the alt, It would jolt it while you depressed the foot switch. You would still need a diod in the line to keep it from back feeding once the alt is making juice.

[Bill pilot99]

I went with a 12 volt generator and regulator, looks just like the 6 volt.

[Don Coatney]

I keep forgetting the trucks have that foot thing. So I guess it you went from the big post on the starter up to the alt, It would jolt it while you depressed the foot switch. You would still need a diod in the line to keep it from back feeding once the alt is making juice.

Greg;

I think the big post on a foot starter is hot all the time.

[MBF]

Yes it is! Mike