Alternator

[69furyIII]

Hello, I have a 1969 plymouth fury III,it has a round back single field alt, but now when I bout new alternator today the only have square back with 2 field, I was told to ground on of them to alternator case, is this OK to do , also the tested specs on this unit is idle 47amp and max rpm 79 amp, I have the original battery gauge in the dash, will this alternator cause issues being hooked up to original charge wire, thanks on advance for all the help.

 

[Big_John]

Yes, ground one of the field wires to the housing.

As far as the rest, some will say that you should do some sort of ammeter/bulkhead bypass and some will say you don't need to. IMHO, It's a good idea to do the bypass anyway, because it does take the strain off the bulkhead wiring, but you don't need to drop everything to do it. Get the car running and charging first before any mod.

@cbarge has a good thread on doing the bypass. Underhood Ammeter Bypass Be sure and include the proper fusible link if you do it.

 

[69furyIII]

Ok, thank you

 

[Gerald Morris]

Hello, I have a 1969 plymouth fury III,it has a round back single field alt, but now when I bout new alternator today the only have square back with 2 field, I was told to ground on of them to alternator case, is this OK to do , also the tested specs on this unit is idle 47amp and max rpm 79 amp, I have the original battery gauge in the dash, will this alternator cause issues being hooked up to original charge wire, thanks on advance for all the help.

1. Bypass that ammeter and get a voltmeter, which you can wire off the charging stud or + battery terminal if you're really concerned about charging voltage. The MAD bypass probably is the most common, canonical bypass method. I improved on that a little, by lugging both conductors on the ammeter together and feeding ALL the system current directly to these, making sure to disconnect all other feeds through the firewall, from either battery or alternator. I use a large conductor, #10 AWG minimum, though I used #8 for our current driver, Gertrude. This makes for a robust, safe method of feeding all circuits, as one provides current to both the old battery fed and alternator fed circuits, in effective parallel, by this approach. I use a fusible link, 2 even AWG sizes smaller than my main feed, at the battery, which is where the feed comes from. I then charge the battery directly off the charging stud with the same size conductor, running it in FRONT of the radiator, to separate it from any old conductors. Again, MAKE SURE ALL OTHER FEEDS HAVE BEEN REMOVED, AND IF NECESSARY, CAPPED OFF! There should be ONE conductor leading to the battery, then ONE through the firewall to the lugged together red and black wires which formerly fed through the ammeter. The, the Morris Bypass.

2. Make double SURE that your conductors are large enough to handle the ampacity of the new alternator.. If your new one can produce 79 amperes at ~14.6 VDC, then lengths of #10 AWG will work, IFF they're no greater than 5 feet. If using #10, use a #14 AWG fusible link/ If using #8, use 12 gauge. Low voltage systems like our cars require careful consideration of ampacity.