12V Alternator Issue

[ChrisFromCLE]

I’m scratching my head about a 12V alternator on my other tractor, a Farmall Cub. I know that this is the N Series Forum but we have a wealth of conversion experience not found elsewhere. Hopefully you can help me figure this out.

It has a Ford three wire alternator with a Transpo f7078 voltage regulator/one wire converter. The regulator is hooked up properly, BK to ground, RD to BAT, GN to FLD, and YW to STA. The alternator will not charge unless I spark FLD to BAT. Then it charges fine - 14V at the battery terminals. When I turn the tractor off, it returns to not charging - the polarization does not stay.

I added an indicator light by wiring + to switch, to light (26 ohms), to the OR wire on the regulator. When the switch is turned on, the light illuminates. When the tractor is started, it stays on, the alternator is not charging. With the light on I have zero volts from FLD to ground. When I spark FLD to BAT the light goes out and charging begins.

What is wrong here? What am I missing? Does the regulator have an internal failure?

I appreciate your insight and expertise.

Chris from CLE

 

[Jim.ME]

The alternator does not polarize like a generator, it needs power to the field to start charging,as shown to you by it starting to charge when you spark the field flAttery positive.

Try hooking the wire from the indicator light to the field terminal and see what happens.

 

[old]

I’m scratching my head about a 12V alternator on my other tractor, a Farmall Cub. I know that this is the N Series Forum but we have a wealth of conversion experience not found elsewhere. Hopefully you can help me figure this out.

It has a Ford three wire alternator with a Transpo f7078 voltage regulator/one wire converter. The regulator is hooked up properly, BK to ground, RD to BAT, GN to FLD, and YW to STA. The alternator will not charge unless I spark FLD to BAT. Then it charges fine - 14V at the battery terminals. When I turn the tractor off, it returns to not charging - the polarization does not stay.

I added an indicator light by wiring + to switch, to light (26 ohms), to the OR wire on the regulator. When the switch is turned on, the light illuminates. When the tractor is started, it stays on, the alternator is not charging. With the light on I have zero volts from FLD to ground. When I spark FLD to BAT the light goes out and charging begins.

What is wrong here? What am I missing? Does the regulator have an internal failure?

I appreciate your insight and expertise.

Chris from CLE

Is your alternator a Delco 10S! if so it has to have 3 wires hooked up to work. The charge wire which goes to the amp gauge the excite wire which turns the alternator on I.E. FLD wire and then the sense wire which tells the alternator when to stop/slow down on charging

 

[Jim.ME]

Is your alternator a Delco 10S! if so it has to have 3 wires hooked up to work. The charge wire which goes to the amp gauge the excite wire which turns the alternator on I.E. FLD wire and then the sense wire which tells the alternator when to stop/slow down on charging

It is not a Delco 10SI. He clearly posted "It has a Ford three wire alternator with a Transpo f7078 voltage regulator/one wire converter." in the post you quoted.

 

[Jim.ME]

I’m scratching my head about a 12V alternator on my other tractor, a Farmall Cub. I know that this is the N Series Forum but we have a wealth of conversion experience not found elsewhere. Hopefully you can help me figure this out.

It has a Ford three wire alternator with a Transpo f7078 voltage regulator/one wire converter. The regulator is hooked up properly, BK to ground, RD to BAT, GN to FLD, and YW to STA. The alternator will not charge unless I spark FLD to BAT. Then it charges fine - 14V at the battery terminals. When I turn the tractor off, it returns to not charging - the polarization does not stay.

I added an indicator light by wiring + to switch, to light (26 ohms), to the OR wire on the regulator. When the switch is turned on, the light illuminates. When the tractor is started, it stays on, the alternator is not charging. With the light on I have zero volts from FLD to ground. When I spark FLD to BAT the light goes out and charging begins.

What is wrong here? What am I missing? Does the regulator have an internal failure?

I appreciate your insight and expertise.

Chris from CLE

This drawing should match how you have the alternator wired currently as I read your post.

 

[Duner Wi]

This drawing should match how you have the alternator wired currently as I read your post.

View attachment 162296

Application guide for those interested F7078
Applications

• American Motors (1976-1978)
• Ford (1969-1985)
• Lincoln (1972-1978)
• Mercury (1972-1985)

 

[ChrisFromCLE]

This drawing should match how you have the alternator wired currently as I read your post.

View attachment 162296

Yes, wired exactly like this.

Chris from CLE

 

[Duner Wi]

Try a bulb that draws more ohms like a 194 bulb.

 

[Jim.ME]

Try a bulb that draws more ohms like a 194 bulb.

Good point. He should tell us what the bulb in his indicator light is. If he used an LED it won't work, at least I have not had any luck using an LED indicator light for such applications.

 

[ChrisFromCLE]

Good point. He should tell us what the bulb in his indicator light is. If he used an LED it won't work, at least I have not had any luck using an LED indicator light for such applications.

It is an incandescent lamp, sealed unit so not sure of the wattage but it measures 26 ohms, I thought about needing more resistance so I tried it with two lamps in series. Is it possible that even 52 ohms is not enough?

Thanks,

Chris from CLE

 

[Jim.ME]

It is an incandescent lamp, sealed unit so not sure of the wattage but it measures 26 ohms, I thought about needing more resistance so I tried it with two lamps in series. Is it possible that even 52 ohms is not enough?

Thanks,

Chris from CLE

Two should have provide enough resistance. You may have a bad regulator/one wire converter.

 

[ChrisFromCLE]

Two should have provide enough resistance. You may have a bad regulator/one wire converter.

Thanks for your insight Jim. I will pull it again on Monday.

Chris from CLE

 

[Jim.ME]

My personal choice would be to replace it with a Delco 10SI, three wire (or one wire). Easily found replacements if there are issues. With the 1G "Ford" you are always going to be dealing with an external regulator as well as the alternator. Again, just my choice, others are free to choose for themselves.

 

[Duner Wi]

Have you tried over 2000RPM. If nothing else works a Ford electronic voltage regulator would be easy enough for me to figure out.

Warning light, no warning light , Too small an amp draw and warning light bulb may not be a factor in getting Transpo F7078 to excite to start charging.
I would try a quick blip to at least 2000 RPM and see if it kicks in.

 

[ChrisFromCLE]

Have you tried over 2000RPM. If nothing else works a Ford electronic voltage regulator would be easy enough for me to figure out.
View attachment 162414
Warning light, no warning light , Too small an amp draw and warning light bulb may not be a factor in getting Transpo F7078 to excite to start charging.
I would try a quick blip to at least 2000 RPM and see if it kicks in.

Thanks for the response. I did try that. No change even at full throttle.

Chris from CLE

 

[Duner Wi]

Thanks for the response. I did try that. No change even at full throttle.

Chris from CLE

If you search the Internet regarding F7078 Transpo ,you are not the only person having difficulty getting them to kick in .Here is diagram from 1976 Motor Manual.useing factory regulator.

 

[ChrisFromCLE]

If you search the Internet regarding F7078 Transpo ,you are not the only person having difficulty getting them to kick in .Here is diagram from 1976 Motor Manual.useing factory regulator.View attachment 162441

Duner,

Thanks for the schematic. I’ll give the guy who sold me the Transpo one more chance. If that fails I will change the regulator using this drawing.

Thanks,
Chris from CLE

 

[Duner Wi]

Pigtail for regulator, Wells #1P1131. If F7078 doesn't work out in the end. The yellow A+ wire connects near the battery to battery +. This is remote sense wire. Connecting near the battery gives best results over long term. To excite alternator 194 bulb or equivalent .Do you really need want the idiot light ? There are other ways to excite alternator. Post back if you get F7078 working and how . Thanks