Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 06-22-2019, 04:53 PM   #1
mngreen
Senior Member
 
mngreen's Avatar
 
Join Date: Jul 2010
Location: Rancho Santa Margarita, CA
Posts: 138
Default Problem with alternator

I replaced my Delco 10-DN alternator with a remanufactured one recently since the bearing was shot and making a lot of noise. I have an old mechanical Delco voltage regulator on the firewall. 12V system. Battery is good and fully charged.

The "new" alternator charges correctly; goes up to 10 amps then tapers down to zero as it should. However, once the engine goes to idle, it registers a 10 amp discharge and stays there at idle until I hit the throttle again, when it then charges and tapers back to zero, as long as I am throttled up. I do not get a discharge when the engine is off and ignition switch is off, so I surmise that there is no voltage loss other than in the charging circuit.

Perhaps the remanufactured unit has some diodes burned out?? Or might a bad regulator be the culprit? The old alternator did not do this and I did not change the wiring (2-wire setup, I think, no idiot light).
mngreen is offline   Reply With Quote
Old 06-22-2019, 06:20 PM   #2
1931 flamingo
Senior Member
 
1931 flamingo's Avatar
 
Join Date: May 2010
Location: new britain,ct 06052
Posts: 8,020
Default Re: Problem with alternator

It needs to be "excited" in order to charge. That's normal.
Others will "chime" in I'm sure.
Paul in CT
1931 flamingo is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 06-22-2019, 07:14 PM   #3
mike657894
Senior Member
 
mike657894's Avatar
 
Join Date: Oct 2015
Posts: 850
Default Re: Problem with alternator

the alternator should hold excite once reved over 1000 rpm. I would blame the regulator or other parts on the back of the alternator. The remanufactured alternators are hit and miss these days. My model A got a good one first try. My farm truck is on its third funky one. Rewired the circut isolated thinking I couldn't get 3 bad ones. The farm trucks one is doing what yours does. take it back, mark it with a sharpie to make sure they are not cycling them on the shelf.
mike657894 is offline   Reply With Quote
Old 06-22-2019, 07:17 PM   #4
mike657894
Senior Member
 
mike657894's Avatar
 
Join Date: Oct 2015
Posts: 850
Default Re: Problem with alternator

I believe for your standard chev alt to work right it needs the light. it will charge weakly with just the large wire and a jumper to post 2. but for good charging it will need the light. someone may know more than me about them though. http://strategiccontentmarketing.co/...ng-diagram.jpg
mike657894 is offline   Reply With Quote
Old 06-23-2019, 10:23 AM   #5
VinceBlack
Junior Member
 
Join Date: May 2017
Location: Kansas
Posts: 15
Default Re: Problem with alternator

Alternator is not turning fast enough to stay excited at idle, just like the old Chrysler systems did in the 60s and 70s. The unit you bought might have a 2 amp rotor which will take more rpm to saturate stator coil to start charging. Installing a smaller pulley might help. Sounds like system is charging fine when rpm increased. A 10si self exciting one wire alt is also an option.
VinceBlack is offline   Reply With Quote
Old 06-23-2019, 11:48 AM   #6
katy
Senior Member
 
katy's Avatar
 
Join Date: Jun 2015
Location: Alberta, Canada
Posts: 1,975
Default Re: Problem with alternator

If your old alternator works good, other than the noisy bearing, why don't you just replace the bearing(s) in it. Not hard to do.
__________________
Don't go away mad, just go away.
katy is offline   Reply With Quote
Old 06-24-2019, 09:11 AM   #7
Badpuppy
Senior Member
 
Join Date: Dec 2017
Location: Guthrie, OK
Posts: 431
Default Re: Problem with alternator

Mike's reference is for a built-n regulator, like the 10SI has. Vince is spot on - check pulley size. katy has the simplest solution, probably.

So long as you don't leave it idling until the battery dies, it won't hurt anything. Like the salesman says, "That's not a problem, that's a FEATURE!"
Badpuppy is offline   Reply With Quote
Old 06-24-2019, 09:52 AM   #8
30 Closed Cab PU
Senior Member
 
Join Date: Aug 2018
Location: Wisconsin
Posts: 1,264
Default Re: Problem with alternator

If the other suggestions do not work, As Vince mentions above, try a smaller pulley.


I believe the venders have them, and it is common when converting from generator to alternator to also change the pulley to overcome/partially overcome the excitation min voltage.
30 Closed Cab PU is offline   Reply With Quote
Old 06-24-2019, 12:27 PM   #9
mngreen
Senior Member
 
mngreen's Avatar
 
Join Date: Jul 2010
Location: Rancho Santa Margarita, CA
Posts: 138
Default Re: Problem with alternator

Well, problem solved, for now....

Swapped back to the old alternator. Negligible discharge at idle and charges good and tapers off, so no problem with the regulator. Maybe the squeaking bearing will go away and was just a too tight belt or maybe even the weather! At least it's not squeaking now.... I think Vince's post is spot on.

Lesson learned...you get what you pay for! $40 for "remanufactured" Chinese crap was just that...CRAP!
mngreen is offline   Reply With Quote
Old 06-24-2019, 10:04 PM   #10
VinceBlack
Junior Member
 
Join Date: May 2017
Location: Kansas
Posts: 15
Default Re: Problem with alternator

Front bearing is a 203RS, NB11 for rear.
VinceBlack is offline   Reply With Quote
Old 06-25-2019, 09:26 AM   #11
mngreen
Senior Member
 
mngreen's Avatar
 
Join Date: Jul 2010
Location: Rancho Santa Margarita, CA
Posts: 138
Default Re: Problem with alternator

Thanks to all...


and Katy, I might just cannibalize that new alternator for its bearings!
mngreen is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 06:16 AM.