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Hi
I have an ‘87 motorhome with an E-350 nose. I believe it has a 2g alternator which is like to upgrade. It has an ammeter on the dash as well. From what I see online, it looks like I can do it, but I have reservations. First, it has a single v-belt to drive the alternator. I’m thinking I might have to change the crank pulley to use a 2v groove pulley. Second is the ammeter. What I read was to bypass it because it would deflect too much and probably peg the meter. My thought on this was to shunt it so only a portion of the current would go through it, thereby allowing me to still see charge/discharge rates without overloading the meter. Any thoughts on this approach?
Thx
Bruce
 

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Sometime increasing alternator capacity on a single V-belt can result in squealing. The two V-belt arrangement would be good if it could be done. Proper shunting would likely allow the continued use of the ammeter. The alternative is to switch to a voltmeter.
 

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I switched over to a large cased 130 amp 3G alternator on my BBF in my '79 Ranchero, it also had V-belts and ammeter. The V-belt will work OK as long as you don't pull over 80 amps +/-, above this the belt tends to slip, I tried to roughen the inside of the alternator pulley with sand paper and it did help for a while. I tried to install a 2 belt pulley on my 3G alternator but found there was not enough thread engagement for the alternator pulley nut due to the thickness of the pulley and/or the alternator's shaft length, there may be another pulley(pulley thickness) option for this, I just never found one. The ultimate fix was to modify my original 3 sheeve crankshaft pulley to accept a 6 rib sheeve to run the alternator, no more squeal. As far as the ammeter goes, or really the shunt involved, I would suggest to get rid of it. The shunt in my application was basically a 10 ga wire that was run between the junction post and the battery side of the starter solenoid. This 10 ga wire my be fine with a 55-65 amp alternator but with a 95-130 amp 3G it will become a restriction and a potential fire hazard. Now you can modify the shunt wire and upgrade to an 8GA or better yet a 4GA cable, but I chose to convert my ammeter to a voltmeter. Here's a couple pics, hope this info is helpful.


 

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This is a fairly easy swap, did same to a 110A on our 1993 F-350 460. That is a serpentine setup, so there was no pulley swaping. I put a 100A breaker between the replacement alternator and the battery just for a bit of safety. Wiring is not complicated, plenty of diagrams found online with a little search. Alternator was $45 out of the sea crate full of alternators at the wrecking yard. Dropped right in place.
 

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Can someone please let me know a car that these large frame alternators came in? Going to the yard this weekend and will most likely run into a couple different tauruses and contours and such.
 
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