12v conversion woes

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coppersmythe
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Re: 12v conversion woes

Postby coppersmythe » Sun Mar 01, 2015 1:35 pm

EUREKA :!: the problem turned out to be the voltmeter I bought from the local autozone ( bosch auto aftermarket gauge $19.99 ) . I went to tractor supply and found a 30 amp AMMETER ( sorry guys , I have been using the wrong term ) tsc sku# 0236601 for $ 9.99 . Works perfectly , wrench stuck firmly to the back of the alt. ( thanks boss ) . it jumped to about 25 amps , then slowly went down . the voltmeter was acting as a "restriction" to the flow . I thank everyone for the help . coppersmythe...............PS: I even lucked up and didn't have to switch the wires on the ammeter.

coppersmythe
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Re: 12v conversion woes

Postby coppersmythe » Sun Mar 01, 2015 1:40 pm

john , the schematic I used does not have the 1 and 2 wire coming off the alt. , it does not have the light . it does show the ballast resistor , but I did not use one , I bought a coil with internal resistor . I cant remember where I got it (schematic) , but it looks exactly like the bob Melville # 5 , but without the above mentioned wires .coppersmythe............................................

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Re: 12v conversion woes

Postby Bus Driver » Sun Mar 01, 2015 6:23 pm

The voltmeter will pass only a fraction of a milliampere of current. No wonder the alternator appeared to be not charging.
While analog ammeters and voltmeters do start with the same basic meter movement, voltmeters have a significant resistance connected in series with the meter and ammeters have a low resistance connected in parallel with the meter.
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Re: 12v conversion woes

Postby ScottyD'sdad » Sun Mar 01, 2015 6:59 pm

Isn't a voltmeter what people have been saying we should be using, as a more accurate reading of output? I've used higher reading ammeters, in the ones I've done, but I'm sure I read volt meters, here.
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Re: 12v conversion woes

Postby Bus Driver » Sun Mar 01, 2015 10:01 pm

It is assumed that the voltmeter was connected as the ammeter was originally connected-- thus the voltmeter was the only current path between the alternator and the battery. A voltmeter properly installed has one connection to ground and requires a means to be disconnected when the engine is not running in order not to discharge the battery over time. For the Cub, I think either instrument is adequate to show whether charging is occurring. But it is crucial to note that the normal voltage while running is about 2 volts higher than with the engine stopped. Same voltage running and not indicates a charging problem.
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coppersmythe
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Re: 12v conversion woes

Postby coppersmythe » Mon Mar 02, 2015 6:19 am

bus driver is spot on , as usual . I connected it as the diagram shows to connect the ammeter . I hope this thread helps others to avoid these problems . the sad thing is , I was digging around the shop last night making a mental inventory of my electrical "stuff" . I find an unmarked box , inside was a brand new IH 12v voltmeter 2" gauge . :oops: coppersmythe..................................PS: I will do my homework before tackling the '48 restoration wiring .

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John *.?-!.* cub owner
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Re: 12v conversion woes

Postby John *.?-!.* cub owner » Mon Mar 02, 2015 10:22 am

That is called experience. How do you think we know what to ask when someone has a problem. We weren't born with that info. Some people learn by watching others, some by reading, but some of us that just have to pee on the electric fence ourselves. :oops:
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Re: 12v conversion woes

Postby danovercash » Mon Mar 02, 2015 1:01 pm

Is that like making things happen, watch things happen or wondering what happened ! Lol. John. Which one are you?
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John *.?-!.* cub owner
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Re: 12v conversion woes

Postby John *.?-!.* cub owner » Mon Mar 02, 2015 5:42 pm

danovercash wrote:Is that like making things happen, watch things happen or wondering what happened ! Lol. John. Which one are you?
Guess!!!!!!
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Re: 12v conversion woes

Postby Boss Hog » Mon Mar 02, 2015 7:18 pm

I do not know who started the hype with the voltmeter but IH never had one on a cub as far as I know. And that is good enough for me :D
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John *.?-!.* cub owner
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Re: 12v conversion woes

Postby John *.?-!.* cub owner » Mon Mar 02, 2015 9:30 pm

With an alternator a volt meter has it's advantages. Keeping an eye on the voltage both while running and stopped gives you a better idea of what is happening with both the battery and the charging system. Not just that it is charging, but whether it is under or overcharging, in addition to how well the battery is staying up when setting.
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Re: 12v conversion woes

Postby artc » Tue Mar 03, 2015 5:54 pm

I dislike ammeters for the following reason - if the ammeter says "0" while the tractor is running - you do not know if it is because the alt/gen has fully charged the battery or is just dead. so in essence it tells nothing about the condition of the battery or the charging system unless its charging just after start-up. conversely, a voltmeter at 10 volts tells you the battery is weak, at 12.6 all is well engine off, and at 14.4 running its charging. that is one reason you do not see ammeters on cars since the 1960's. but you have to connect them differently, as this thread points out. an ammeter is in series with the load, and a voltmeter is connected from +12 to ground.
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Re: 12v conversion woes

Postby Bus Driver » Tue Mar 03, 2015 8:05 pm

Given that most Cubs still have ammeters and no doubt will continue to do so, a simple test of the ammeter while running is to turn on the lights. The ammeter needle should show a response at that moment.
The GM 10 SI alternators no longer are plentiful at wrecking yards. I bought several many years ago and some of them were of higher amperage. Only one required service and that was just new bearings. On a Cub, a 55 amp alternator barely responds to the lights being switched on. But the engine is a bit more loaded if one listens carefully. The rear flasher makes the ampere needle quiver slightly. That shows me that the rear flashing light is working.
No matter which gauge is used, it is necessary to be able to interpret the meaning of the readings displayed.
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