Ford alternator adaptation

[3oo3]

I have installed an '03 Ford Mustang engine into a Model A and have utilized the '03 alternator. The Mustang gauge was originally installed inline in the regulator circuit and had a resistance of 490 ohms. I replaced the original Mustang gauge with a carbon resistor of 500 ohms. I have installed VDO gauges which use a voltmeter. Voltage in a static condition indicate 12 volts on the VDO gauge. Running it shows 14. The battery is new and has had limited run time so it is possible that it does not have a full charge. My concern is that the battery is being overcharged??? I do not know the accuracy of the carbon resistor. Would it be reasonable to replace the resistor with a potentiometer (0-500 ohm) to control the voltage?
Thanks, 3oo3

 

[MikeHalloran]

Normal voltage in a '12V' system with the engine running and the battery fully charged is ~13..14.5 volts, depending on the temperature. With the engine off and the battery fully charged, voltage should be ~12 volts, depending on the temperature.

With respect to the 'carbon resistor' and the 'Mustang gauge', at least one of us doesn't know what you are doing, or trying to do. Can you get some local help?





Mike Halloran
Pembroke Pines, FL, USA

 

[Comcokid]

From my experience in the past designing gauges, although the market views VDO with high quality, (and they are well built), they frankly are least accurate of the gauges on the market. And, all the gagues on the market are just that - gauges, and not precision instruments. If you want to really know what the voltage is, use a hand-held meter

And, as Mike Halloran points out, we may refer to automotive systems as "12 Volt", but the actual voltage is a little higher.

 

[patprimmer]

Mike

Make that 2 of us that don't know what he is doing.



Regards

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[3oo3]

I am going to vote with the majority that the originator of this thread (me)does not know what he is doing and that is why he is posting here. My limited auto electrical training (40 years ago) always stipulated that the output voltage of the alternator should not be over 13.4 volts. Voltage higher than this would create a overcharge condition. The Mustang regulator circuit with the INLINE gauge (R500)is sourced to a dedicated 15A fuse and I came to believe that the resistance of the gauge influenced the output of the alternator. This assumption may be totally wrong???? I have read other sources stating that voltage in modern vehicles is running a high as 14.5 volts so maybe what I have is doing exactly as it should. I guess the next question is what effect if any does the inline resistance (gauge)have on the output of the alternator???? What would happen if I removed the resistor???? The load on the system is very low (ignition only 99% of the time)and I do not want to cook the battery. Thanks for your input. 3oo3

 

[MikeHalloran]

I don't think that presence or absence of that gage should affect the system voltage.

Have a look at the schematics for the donor car. A lot of alternators today have internal regulators, as I suspect yours does. You have to work hard to modify the performance of systems like that, and mostly they work well enough that you shouldn't feel the need.

If you're still nervous about cooking the battery, just leave the headlights on.



Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

If it's putting out less than 14.7 volts it won't cook the battery, at least not so long as the battery is not also to close to a high heat source.

I have some recollection of old fashioned amp meters that had a resistor in parallel. I am sure that a google search would throw up a diagram.

Regards

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[evelrod]

I don't have a "Mustang" engine in my 1930 Ford, but I DO have a late model Ford alternator and a 12v electrical system. The installation is as bare bones as you can get, one wire using the OEM loom. I use the stock instrument (ampmeter) and the stock 6v starter motor. The only resistor is a 6v drop for the original 6v horn motor.
I replaced the 6v coil with one compatible with the 12v system without the need of a separate ign resistor along with a set of 289 points and condenser on a modified breaker plate to replace the Model A stuff. Sorry, I don't see a problem.
It's been doing fine now for several years.

Rod

 

[patprimmer]

Rod

How do you turn the windscreen wipers off.

Whenever I ran 12 volts through a 6 volt wiper motor they went so fast they ran through the parked zone then continued to the park position, then through it again.

Regards

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[evelrod]

Vacuum mtr., Pat. I rebuilt the OEM Ford mtr. with a NOS kit I found at a swap meet originally intended for a Dodge. I lube it with Vasoline. My problem, as it refers to rain, is cured by just not driving the A in it. Also I use lots of Rain-X, just in case.

Rod

 

[patprimmer]

My experience was converting VW Beetles from 6V to 12V.

They all had electric wipers and I needed to swith the main power line to stop them. This bypassed the park feature.



Regards

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