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Ford 9N, 2N & 8N Discussion Forum
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alternator spin backwards?

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RMD

07-26-2004 20:38:17




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1942 9N w/ 12v conversion. Facing the front of the alt. the pully is turning clockwise. But the cooling fan blades are backwards as though the alt should be spinning the other way. Will an alternator charge turning either direction, or do they only work one way? This one does not charge.
Thanks in advance for any help!




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Jim Cox

07-28-2004 06:58:16




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 Re: alternator spin backwards? in reply to RMD, 07-26-2004 20:38:17  
get a 12SI fan from a mom-and-pop shop, should be under $15. You want to make sure you have the type 110 automotove brush holder, they can go either direction. The type 116 prefer CW, but last longer. That's why we use them in our Reman Ag alternators. Either way, all our 10SI thru 22 SI Delcos spin CW. We put 100% new fans on the 10SIs we reman

Jim Cox
Product / Applications Engineering
CNH Reman Electrical

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Bob

07-26-2004 21:52:51




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 Re: alternator spin backwards? in reply to RMD, 07-26-2004 20:38:17  
You didn't mention what make of alternator you have, but that shouldn't matter, as virtually all of them will charge the same in either direction, and furthermore, clockwise SHOULD be the standard direction for an alternator to turn. The problem would come if the alternator were to be run CCW because many common alternators (Delco for example) do not have the drive pulley keyed to the shaft, and given a little time with the pulley driven CCW, the nut would work loose, and the nut and pulley would spin off!

Most alternator fans are designed with the fins sloped so the outer end trails the inner end, when run the usual CW. This is because the fan draws air OUT of the front of the alternator, and air rushes in the back side of the alternator, cooling the rectifiers and the regulator first.

Looking at your alternator, is this how the fins on the fan are arranged?

Anyhow, almost certainly, CW rotation is NOT the cause of your alternator not charging.

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duey

07-26-2004 21:52:07




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 Re: alternator spin backwards? in reply to RMD, 07-26-2004 20:38:17  
It is turning the right way, that is the way the hand crank turns, the same way driveshafts turn, too. But techically it doesn't care, one that is working is waving a magnetic field past a pile of coils without regard to direction. The diodes straighten out this mumbo jumbo of electron flow and gives a half decent form of direct current out the big bolt.

Now a generator, he's a bit more fussy....

Most of these little tractors don't provide too much load for an alternator, and they don't need tons of cooling... they about hang out in the open air as it is. duey

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RMD

07-27-2004 19:29:25




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 Re: Re: alternator spin backwards? in reply to duey, 07-26-2004 21:52:07  
Thanks for all the good info guys! I about figured all that out cause I took the alt in to a parts house and had it checked. It is putting out 14 volts on their machine. I put it back on the tractor and wired it all up and it charged. BUT! I put a voltmeter on the back side and also checked the voltage at the battery terminals with the tractor running and it was reading 17.5 volts! It was charging at 30 amps according to the amp meter. The battery was fully charged before I started the tractor, so it shouldn't need to charge so hard. Afraid that is going to fry the battery! Anyone know what is wrong? It is a Delco Alternator like in a chevy pickup. I have the P1 terminal hooked to the ignition switch and going through a momentary toggle switch, and P2 hooked to the Bat terminal on the back of the alternator. Again, Thanks!

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Bob

07-28-2004 06:51:25




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 Re: Re: Re: alternator spin backwards? in reply to RMD, 07-27-2004 19:29:25  
A couple of things...

Is your battery top wet from electrolyte boiling out from over charging? (Which would definitely be a sign of overcharging.)

Are you using a digital meter? Some digital meters don't like all the electrical noise from the alternator and the ignition system. It makes them read funky!

Does the battery seem in good condition, and does it have enough capacity to spin the engine over well? What is the battery voltage after it sits overnight, and before you start the engine? It should be very close to 12.5 Volts. If the voltage is lower than that, it can indicate a bad cell, which can affect the internal resistance of the battery, and give odd readings when it's being charged.

If the shop that tested the alternator knows what they are doing, my first bet would be "digital meter with a headache syndrome".

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RMD

07-28-2004 20:01:43




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 Re: Re: Re: Re: alternator spin backwards? in reply to Bob, 07-28-2004 06:51:25  
Thanks for the reply. The battery is not boiling over and is a fairly new battery. I was checking with a digital meter so that could be the cause of the bad reading. After sitting overnight, the battery voltage is 12.8 volts. The two side terminals on this alternator are not labeled at all with a P1 or P2, so I wonder if I have them reversed. With the traqctor not running and the key in the off position, I get a slight negative reading on the amp meter, as if a drain of some sort. If I disconnect the side terminals from the alternator, the drain goes away. Again, Thanks!

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Bob

07-29-2004 00:05:37




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 Re: Re: Re: Re: Re: alternator spin backwards? in reply to RMD, 07-28-2004 20:01:43  
With the two terminals facing "UP" (12 o'clock), the LH terminal is #1 and the RH terminal is #2 (when viewed from the back of the alternator).



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