diode in a 12v system

[whizzernick]

I need a little help. I just changed my 33 ford from 12v - ground to 12v + ground now it seems that the generator will not charge. I am also thinking about a diode instead of the cut out . will a diode charge both + or - ground ?

[ford38v8]

Nick, you may have fried your cutout points if you ran the engine without having polarized the generator first. What better time to put on a diode, right?

[Bob C]

Originally Posted by whizzernick

I need a little help. I just changed my 33 ford from 12v - ground to 12v + ground now it seems that the generator will not charge. I am also thinking about a diode instead of the cut out . will a diode charge both + or - ground ?

Yes but you have to turn the diode around.

Bob

[mrtexas]

Diode only allows current to go in one direction. If put in the wrong direction the diode will burn up.

[BillM]

Originally Posted by mrtexas

Diode only allows current to go in one direction. If put in the wrong direction the diode will burn up.

So if you connect it correctly it will conduct and if connected wrong it won't conduct, so how will it burn up?
If you conduct more current or apply more voltage than its rated for it will burn up.

[Bob C]

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Did you polarize the generator after you switched the ground? Also need to
switch the wires on the ammeter and coil.

Bob

[terry]

you can get a 12v pos ground regulator from Fun Projects. It looks exactly like your cutout and goes right on top of the generator. If you haven't changed the generator to 12 v, you need to be careful and limit the total am't of amps you are using. The unit comes with good directions on how to avoid this. Terry

[koates]

wizzer, Seems a bit strange to me that you would change your 1933 Ford from 12 volt negative ground (a modern standard) to 12 volt positive ground which is not normally used very often. What is the reason for your change ? The original car when new was 6 volt positive ground. The diodes used in replacement modern cut outs are usually alternator main diodes which come in both negative polarity and positive polarity type. Not all modern diode cut outs are good quality. Some have very small flat looking diodes/transistors which are only able to handle 5 amps or so and are basically crap. You have to buy the ones with the large alternator diodes inside which will handle 20 plus amps. As terry says the FUN PROJECTS voltage regulator (round type Ford) that mounts on top of the generator is a good option. They come in 6 or 12 volts and pos. or neg ground which you would have to stipulate when ordering one. They only work with a third brush generator. Regards, Kevin.

[whizzernick]

thanks for all the response. I just bought a diode kit from C & G . Kit was from Ralph Heinze . I checked with him and was told that the diode was rated at 50 amps & up to 50 volts. I have installed in original ford cut out. testing with a 12V battery electricity will only go one way. but polarity must be correct. I am not sure why . I also need to know why you have to polarize and how do you do it . IM old and forgot.
One other question can an amp gage burn up (original ford loop type )

[JSeery]

No on the amp gauge "burning up", there is no current going through it. The gauge just senses the magnetic field around the wire that passes through the loop. It may not be working, but it is not "burn up".

I'm not totally sure I understand your diode question. Do you understand what a diode does? It only allows current to flow in one direction and blocks it in the opposite direction. So, the diode should be blocking the current flow and allow it to only flow in one direction, that is the whole idea of installing one in the first place. If it is blocking current in the wrong direction then it is installed backwards. You really should consider purchasing an electronic cut-out where all of these issues are taken care of for you.

You polarize a generator to be sure it is functioning with the same polarity as the rest of the system. There have been threads posted in the past on polarizing procedures, I am not able to post that information at the moment. I would think a quick internet search on how to polarize a generator should do the trick.

[whizzernick]

thanks I will try that

[rotorwrench]

When the 12-volt generators started coming on strong in 1955, they had three pole voltage regulators and were 2-brush systems. If this is a 3rd brush type system, you generally flash between the two terminals on the cut out.

A generator has field pole shoes that magnetize to a certain amount of gause when they are properly polarized. This residual magnetism is what pulls the cut out into the closed circuit position after the engine is started. Without that residual magnetism the generator can't come on line. A person needs to know if they have a 3-brush set up or a 2-brush set up to control it properly. If this was a 12-volt conversion, you have to know how it was converted to get the right stuff. Personally, I would never use a positive ground system for a conversion. Polarity is important for modern electronics and things connected in wrong can get fried.

It the diode is connected the wrong way, the generator can motor until it fries itself. A person needs to know his system pretty well before he tinkers with it.

[JSeery]

Originally Posted by rotorwrench

It the diode is connected the wrong way, the generator can motor until it fries itself. A person needs to know his system pretty well before he tinkers with it.

I agree, that is why I was suggesting an electronic cut-out that is pre-setup for this. You really need to know what your doing to modify it.

Ford V8 Voltage Regulator

Without sacrifice of the original look you can now replace that troublesome generator cutout. Enjoy the luxury of modern day electronics hidden inside an original style generator cutout housing. Cruise with confidence knowing you have a "true field winding control" voltage regulator on your generator and thus protection from electrical system burnout due to overworking of the battery and generator. Designed for the standard 6 volt positive ground system, both a 6 volt and a 12 volt model are available and both are designed to work with the unmodified 6V generator. This makes 12 volt conversion of your car a snap. We now offer both positive and negative ground versions of our 12V regulators.

•No lost "Show" points - exact replacement for generator cutout
•Not just a diode cutout conversion but a complete electronic voltage regulator
•Protects the generator and electrical system from burn out due to overcharging
•Adds years to generator life
•No alterations to generator or car wiring - installs in minutes
•No more dead generator or boiled away battery
•6V Models available with or without Ford script
•12V models now available in negative ground configuration

Is the fist photo what you are attempting to use? The second photo is the Fun Projects Cutout.

[whizzernick]

Thanks again for all the help. To get it clear : My 33 roadster was restored in 1971 , now has over 50 thousand miles . I am now on second eng . I am now finishing up a go threw the car and fix things that have needed repair or upgrade. Rds has been 12 (-) ground for over 20 years. nothing wrong with that. In this upgrade I have replaced battery cables to NOS (original cable ends are designed for (+) ground. the cut out(I have used the very early 33 generator from the start) has given me a little trouble in the past --- so why not upgrade to diode in original ford cutout.. The cables and the cut out make me go to (+ ) ground. I installed cut out yesterday and all is well. One other thing: I have had a dual temp & oil chex gauge in my rds for over 40 years . Around 20 years ago I had a minor short and amp gauge stopped working. I took it apart yester day and found it did burn up ( melted solder connections in side. ( you are right loop gauge will not burn up ) but early amp gauge (post type )will. To day I will install a good oilchex gauge . On my up grade I have replaced front shocks . (old ones were leaking and weak ) I replaced transmission ( original was popping out of second ) I am still using mechanical brakes
I just had to do a major brake adjustment. Next was the gas gauge. Gas gauge worked for about 20 years then stopped. my air line to gas tank tested good. The gas tube in gauge was stopped up. I tried every thing to clear ( any one have a suggestion on this ? ) I ended up replacing gas tube with a good one. I now have a good working gas gauge. Last but not least I replaced engine transmission and rear end fluids with synthetic . I will have my roadster at the upcoming Early Ford V8 western national meet in Bakersfield Ca. Sept 2016 I hope to see some of you there.

[whizzernick]

see diode in a 12v system

[JSeery]

Good to hear your getting it sorted out.