Alternator Wiring Question---P Terminal

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   Hey I was wondering if any "P" terminal will work on an alternator (the manufactor of the alternator doesn't matter) to run a tach off a 7060 tractor. I am using the brown wire where it came off the old alternator on the P terminal with the tach working it just wasnt charging. 
I read the "P" terminal runs the tach on a 7000 series tractor. The tach worked prior to taking it off. The local shop didn't have an exact replacement (4 wire alternator). They sold me a 5 wire alternator with three terminals at the top instead of 2 terminal, and then a ground hook up and a battery hookup. 

The tach doesn't work, and I was just wondering before I take the alternator back off and have them test a new alternator. It charges the tractor just fine, but the tach won't work. Is there a relay in the tach somewhere that might have gone bad? 

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tthams Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 18 Oct 2020 Location: Denison, Iowa Points: 140	Post Options Post Reply Quote tthams Report Post Thanks(0) Quote Reply Topic: Alternator Wiring Question---P Terminal Posted: 15 Jul 2021 at 1:39pm
	Hey I was wondering if any "P" terminal will work on an alternator (the manufactor of the alternator doesn't matter) to run a tach off a 7060 tractor. I am using the brown wire where it came off the old alternator on the P terminal with the tach working it just wasnt charging. I read the "P" terminal runs the tach on a 7000 series tractor. The tach worked prior to taking it off. The local shop didn't have an exact replacement (4 wire alternator). They sold me a 5 wire alternator with three terminals at the top instead of 2 terminal, and then a ground hook up and a battery hookup. The tach doesn't work, and I was just wondering before I take the alternator back off and have them test a new alternator. It charges the tractor just fine, but the tach won't work. Is there a relay in the tach somewhere that might have gone bad?

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jaybmiller Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Location: Greensville,Ont Points: 24335	Post Options Post Reply Quote jaybmiller Report Post Thanks(0) Quote Reply Posted: 16 Jul 2021 at 5:44am
	I'll make the assumption that the 'P' terminal means 'Pulses'...... kinda makes sense to me... need to see a wiring diagram but th e'old skool' in me says.. To test the tach, I'd take a 12-16V transformer ,add a diode, and connect to the Tach and see if the tach works. I used to make custom tachs for my JEEPS and Mustangs,decade ago. B&B Steve probably knows whats in the alternator and how the tach works.
	3 D-14s,A-C forklift, B-112 Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water

steve(ill) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 11 Sep 2009 Location: illinois Points: 85472	Post Options Post Reply Quote steve(ill) Report Post Thanks(0) Quote Reply Posted: 16 Jul 2021 at 8:36am
	I dont think all alternators put out the same PULSE on the P terminal... The output has to be MATCHED to the tack internals.... Probably wrong resistance match between the two. Different alternator is needed.
	Like them all, but love the "B"s.

Steve in NJ Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Location: Andover, NJ Points: 11925	Post Options Post Reply Quote Steve in NJ Report Post Thanks(0) Quote Reply Posted: 16 Jul 2021 at 9:06am
	When it comes to Tachometer's, there is a slew of different signals that different Tachs respond to. First, you have to find out what signal the Tach works off of. Then you match an Alternator to that particular Tach. Some Tach's use what is known as a "pulse generator" to send the signal to the unit. Some do not. Steve is correct on his assumption of the different signals or pulses. As I said, find out what model Alternator is used in that particular application. Once that is established, you then need to look at the break down or description of the chassis and internals. In that information is where you'll find the type of pulse or signal needed to operate that Tachometer. ie- Delco 36SI, or Neihoff LB series, etc. A good Auto Electric store should be able to help you out with that. In some of the older catalogs, there used to be a break down on the different models used. Leece/Neville's used to make me crazy sometimes when matching up an Alternator to a Dump Truck or Firetruck. ... HTH Steve@B&B
	39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife

tthams Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 18 Oct 2020 Location: Denison, Iowa Points: 140	Post Options Post Reply Quote tthams Report Post Thanks(0) Quote Reply Posted: 16 Jul 2021 at 8:20pm
	Thanks for the informative information. I sure learned a lot on this post. I will track down an exact replacement this weekend.