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Discussion Starter #1
I'm replacing my stock alternator with a new Bosch AL7606N (and I did enlarge the alternator bracket to provide clearance for the new Bosch).
The pulley on the new Bosch is slightly larger (about 69mm) than stock (64mm) so thought I'd put a stock sized pulley.

A few questions:
1) Will the pulley on the stock alternator fit the new Bosch and?
2) As I'm keeping the stock alternator as a spare and don't want to cannibalize it and assuming the stock pulley fits the Bosch, does anybody know the part number for another stock pulley to put on the Bosch?
--I thought this would be easy but when I search for new, stock pulleys I get many returns, most of which don't even mention the spec's for the pulley so I'm unable to verify if it's the correct one.

And in case my logic is incorrect and someone wants to correct it, here's why I'm considering installing the stock (smaller) pulley on the new Bosch: I'm not sure if the stock belt will fit over the larger pulley and slightly higher mounted Bosch ....and I figure the smaller pulley will spin the Bosch slightly faster at idle which will be a good thing for current output at idle.

Thanks.
 

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It will fit perfectly. Put the Bosch pulley on the old unit. If the Bosch is a 6 case, you may need to put a couple washers under the mount. Also, you may need to clock the alternator to match the plug orientation. Easy to do.


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Discussion Starter #3
Thanks, that's a good idea.
And I dremeled the alternator bracket slightly so I didn't need to put washers under the Bosch alternator.
For some reason the new Bosch (AL7606N) came clocked the same as my small, stock alternator.
Also adding 1) a cable between both battery positives 2) a cable between the Alt positive and the drivers side positive battery and 3) a cable between the Alt case and drivers side negative battery.
--My stock grounds (from each of the battery negatives to the chassis/engine) look to be in extremely good condition, cable and connection wise, so am not fooling with them for now. Maybe something to do later. We'll see.
My idea with this new, lifetime Bosch alternator is to keep my stock alternator, which is working perfectly fine, as a spare and run the Bosch. If/when the Bosch quits on me I'll install my original and be on my way ...and at my leisure, exchange the Bosch for a new one.
--I've got a digital volt meter so I'll be able to keep an eye on the system voltage and will have warning when the Bosch starts to go ...before it takes down my AGM batteries.
 

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There is already a large cable between the two batteries + terminals. It runs across the front above the radiator. If you run a cable between the driver's + and the alternator, you are giving another pathway from the driver's battery to the starter. Probably won't be a problem, but if the connection on the large existing cable goes bad, you're going to be running the starter through that little cable. I wouldn't do it. On the 6.0, the driver's battery ground goes to the frame. On the 7.3, it goes to the block. That's the optimal way to have it run, so I wouldn't do anything except make sure your cables and connections are in good shape.
 

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Discussion Starter #5
Hi RT,
Yes I know about the 1/0 positive crossover cable between the batteries but thanks for mentioning it ...'cause you never know when you might be missing something obvious.
The cables I'm adding are part of "The Big Three" mod which I've spent the last week or so reading about on various sites. It's mentioned on most of the truck sites. I didn't come across any mentioned downsides to this mod ...which of course doesn't mean there aren't any. I do have a fusable link in the cable between the alternator output and the drivers side positive battery terminal. The "big 3" seemed to be recommended when installing very high output alternators. The Bosch doesn't not qualify as high output at 140A but as I've had 20' of 2 gauge welding cable lying around for the last couple years and a friend with a hydraullic crimper ...and time to fool around, I made the cables up. And I have a camper with some electrical demands and a large-ish amp.
Before installing the cables, I did the following measurements (which I found in post #19 here, Improvements to battery cabling ) and found some voltage differences more than I liked so went ahead with adding more conductors as mentioned above. It could be this "battery cabling improvement" for my particular non-demanding situation is mostly sparkle and not that much function.
 

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Discussion Starter #6
Let's hope it doesn't sparkle too much.
 

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And RT, you know a ton more about this stuff than I do and have answered questions of mine over the years. ...Do you think the above cabling has downsides, even with the fuseable link between the alternator and driver's side positive battery terminal? Thanks.
 

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I think the fuseable link addresses the concerns I had. You might beef up the block to frame and frame to body straps if your camper setup relies on body grounds.

You’ll note that big 3 link you referenced is from the 6.0 forum. Their trucks have the driver’s side battery going to the frame with a weenie cable going from the frame to block. The upgrade really does help that situation.


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Discussion Starter #9
Thanks.
 

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Hi RT, I finished attaching the cables today. I got thinking about the cable from the drivers side positive battery to the alternator + terminal and the alternator + terminal's connection to the glow plugs and starter and what kind of current might run through it (the fuseable link in it now was what I had on hand and is 100A). So put a clamp meter on the cable (drivers side positive battery to the alternator) and turned the key to the "On" position (didn't start it) so as to activate the glow plugs and checked the clamp meter; initially up around 80A and then rapidly decreasing just as you'd expect glow plugs to do. This gave me pause. As I always try to follow the 'first, do no harm' idea and really wasn't sure how much current I'd see through this cable upon start, I disconnected the cable before start up. Once started, I measured the current through my new positive battery terminal crossover cable and the current in the cable added from the alternator case to the driver's side negative and it was interesting watching these current readings as the batteries charged. However despite this "Big 3" mod being done on other 7.3's, I'm still scratching my head over the cable that's supposed to go from the alternator to the drivers side pos battery terminal. I'm thinking if it was connected during start, there'd be a whole bunch of current running through it from the drivers side battery. Not sure that's optimal. ....So on this big three mod, have you ever heard this question come up or been addressed?
--If nothing else, it's been an interesting exercise.
 
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