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12V on idle
https://slantsix.org/forum/viewtopic.php?t=6591		 Page 1 of 2
Author:  Jopapa [ Sun Aug 17, 2003 12:08 pm ]
Post subject:  12V on idle
Well in contrast to my last post about the electrical ("charges like a champ"), it doesn't charge like it should.

When warm it charges great above idle, but at about 900 RPM and lower, it drops to 12V. What manufacturer and part# alts do you guys use to get a full 14V at idle? Or any little tricks to get a full charge?

The stock 80A Denso alt in my truck did a great job, but the housing is way too different to be adapted. The pulley on the new alt in the Dart is pretty small too, so I don't think going yet another size smaller would be possible.
Author:  Pierre [ Sun Aug 17, 2003 12:18 pm ]
Post subject: 
Seems to vary a smidgen day to day, but my alternator does 14v, plus or minus maybe 0.2v at idle. My stock (personally rebuilt) alternator did low 13ish at idle and approached 13.8 with throttle.

Make sure your battery is charged and well or you will be sacraficing alternator output. Consider running a wire directly from the output post of alternator to battery + and redo your measurments from the battery to see if that improves anything. I get a significant, over 1/2 volt, drop from battery to original fuse box because factory wiring isn't exactly ideal, so if I need battery power for an accessory I usually take it directly from battery or from starter, of which I rewired myself with some nice phatty 2awg welding cable.
Author:  Jopapa [ Sun Aug 17, 2003 12:47 pm ]
Post subject: 
Quote:
Consider running a wire directly from the output post of alternator to battery + ...
That was part of my rewiring project 8)

Though I used 10AWG, since it's only a 60A alternator. Connected the charging post to the battery+ on the starter relay, and made a ground strap going from the voltage regulator housing, connecting to the alt's housing, and over to the battery's - post.

Redid alot of wiring in the dash also, to eliminate the ammeter and the remp gauge's wiring.
Author:  Pierre [ Sun Aug 17, 2003 1:01 pm ]
Post subject: 
Well, most if not all stock cars I've worked on didn't do 14v idiling. Infact, I might be more suspicious then happy if a stock alternator did do 14v while idiling.
Author:  Jopapa [ Sun Aug 17, 2003 4:40 pm ]
Post subject: 
Quote:
Well, most if not all stock cars I've worked on didn't do 14v idiling. Infact, I might be more suspicious then happy if a stock alternator did do 14v while idiling.
Really??? You mean on just Mopars, just older cars, or like, everything?

This Dart (and my truck after I put in a 120A alt) is the first one I've seen drop to 12V on idle. Though several trucks I've seen with high output alts have had the idle voltage drop, too...
Author:  Pierre [ Sun Aug 17, 2003 5:07 pm ]
Post subject: 
Yea all cars, usually I see low to mid 13's at idle, then 13.8-14+ when revving. Granted I have not toyed with every single car ever made, but that seems to be the general trend.
Author:  Jopapa [ Sun Aug 17, 2003 6:16 pm ]
Post subject: 
Interesting. Admittedly I haven't worked on a great deal of cars either (and I'm prety sure way less than most people here have worked on), so I don't have very many examples to go by :?
Author:  mighty mouse 63 [ Mon Aug 18, 2003 10:04 am ]
Post subject: 
Using a alternator of unknown orgin (I know its not a rebuilt, but I didn't do the labor) Did you go to duel field? What helped in my case was elimation of the bulkhead connections and bypassing the amp meter. Using good old Die Hard 875cca for cranking chores and will charge at 14.3V at idle and to 13.4 in gear as opposed to the single field setup with 12.5V at idle and 11.9V in gear...Just could be the nature of the beast.
Author:  Jopapa [ Mon Aug 18, 2003 9:39 pm ]
Post subject: 
Quote:
Using a alternator of unknown orgin (I know its not a rebuilt, but I didn't do the labor) Did you go to duel field? What helped in my case was elimation of the bulkhead connections and bypassing the amp meter. Using good old Die Hard 875cca for cranking chores and will charge at 14.3V at idle and to 13.4 in gear as opposed to the single field setup with 12.5V at idle and 11.9V in gear...Just could be the nature of the beast.
Aye, it's dual field. All bulkhead connections (involving the charging system) are gone, with wire going straight in (drilled through the connector so it still looks close to factory) for the dash, and no ammeter.

Too bad you can't get a special pulley with internal gearing that'll spin the shaft even faster...
Author:  Pierre [ Mon Aug 18, 2003 10:29 pm ]
Post subject: 
Why do you insist on 14's when idling? 13ish is plenty. You do realize the current output of the alternator is directly proportional to the horsepower it takes to turn its rotor....
Author:  Jopapa [ Mon Aug 18, 2003 11:44 pm ]
Post subject: 
Quote:
Why do you insist on 14's when idling? 13ish is plenty. You do realize the current output of the alternator is directly proportional to the horsepower it takes to turn its rotor....
Very true. What bothers me is that it drops clear down to 12V on idle, and not low-mid 13s.

That and I'm just anal about such things :?
Author:  Pierre [ Tue Aug 19, 2003 1:39 am ]
Post subject: 
Do you know the history behind this alternator? I know that you can rebuild or rewind them so that they have higher output, but this higher output only comes in at higher rpm and diminishes output at low rpm. Before I bought the gm alternator I called a local shop that does alternators/starters etc for big rigs, and the guy said he could get more juice out of it but it would sacrafice low rpm power.

If battery voltage at idle is same or lower then battery voltage with key off (assuming no accessories are on) then I'd be a bit curious about that alt.
Author:  Jopapa [ Tue Aug 19, 2003 11:53 am ]
Post subject: 
Quote:
Do you know the history behind this alternator? I know that you can rebuild or rewind them so that they have higher output, but this higher output only comes in at higher rpm and diminishes output at low rpm. Before I bought the gm alternator I called a local shop that does alternators/starters etc for big rigs, and the guy said he could get more juice out of it but it would sacrafice low rpm power.

If battery voltage at idle is same or lower then battery voltage with key off (assuming no accessories are on) then I'd be a bit curious about that alt.
I'm pretty sure it's a reman, thoughI can't remember the manufacturer name. I know the girl still has the receipt, so I can check with her later today and have her dig it out. Picked it up at Pep Boys.
Author:  mighty mouse 63 [ Tue Aug 19, 2003 12:03 pm ]
Post subject: 
Jopapa, Wonder if we were separated at birth :?: That is the same technique I used to eliminate my connectors :!: Think were on to something here :idea: ...Dave
Author:  Jopapa [ Tue Aug 19, 2003 12:19 pm ]
Post subject: 
Quote:
Jopapa, Wonder if we were separated at birth :?: That is the same technique I used to eliminate my connectors :!: Think were on to something here :idea: ...Dave
Either that or we used the same article as a reference :lol:
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