Discussion:
Battery voltage drops while running

I have an old Yale G51C with a flathead Continental 163 engine in it. We have been having an issue lately with the battery being dead if we don't keep a tender on it. The tender would always begin to charge immediately after plugging it in. This lead me to believe that either the battery was bad and not taking a charge or the alternator wasn't putting out enough juice to charge.

Today I tried the age old test. The battery was 13.2V with the lift off but if I started the engine it dropped to 8.5V and then slowly worked up to 10.2V. Reving the engine made no difference.

I have had cases before that the voltage stayed the same but never where it dropped.

Bad alternator?
  • Posted 27 Jul 2012 03:00
  • By rslaback
  • joined 25 Nov'09 - 7 messages
  • Wisconsin, United States
Showing items 1 - 11 of 11 results.
no problem bbforks
none taken
he does always have that option to convert to the delco
;o)
  • Posted 27 Jul 2012 23:33
  • By Jplayer
  • joined 12 Apr'07 - 407 messages
  • North Carolina, United States
John Player Jr
_________________
LiftOne, LLC
Charlotte, NC
Email: jplayer@liftone.net
Jplayer- no disrespect- but these Prestolite charging systems ***. I've never had one work as well as the Delco self regualated type. They are troublesome, don't charge well & expensive in comparison. I agree you can get them to work, but dollar for dollar, the Delco is a much better unit.

As far as getting one, my supplier could probably send you one- Contact Torodyne Co.- (215) 598-3105. I'm sure they'll be able to help you- send me an e-mail if you have any questions
  • Posted 27 Jul 2012 10:30
  • Modified 27 Jul 2012 10:33 by poster
  • By bbforks
  • joined 1 Mar'12 - 1,437 messages
  • Pennsylvania, United States
bbforks (at) Hotmail (dot) com
Customers love technology- until they have to pay to fix it!
if the battery is being drained while sitting overnight replace the external voltage regulator, they are notorious for the contacts hanging up. If while running you are getting output from the alternator then dont worry about that, only if there is no output, first put a new regulator on it, check the output, if its ok then your done, if not then you will have to get the alternator repaired as well.
  • Posted 27 Jul 2012 09:52
  • By Jplayer
  • joined 12 Apr'07 - 407 messages
  • North Carolina, United States
John Player Jr
_________________
LiftOne, LLC
Charlotte, NC
Email: jplayer@liftone.net
So is that conversion basically a single wire self exciting alternator like is used a lot of times when converting 6v tractors to 12v tractors? Any help on where I can find that alternator would be appreciated.
  • Posted 27 Jul 2012 09:42
  • By rslaback
  • joined 25 Nov'09 - 7 messages
  • Wisconsin, United States
Those old Yales used a prestolite charging system which was very poor. It also had an external regulator attached to the rear of the alternater. At best the alt would put out maybe 13.5 volts (on a good day). The voltage reading at the battery should be at least 12.5 V with engine running.

Sounds like the alt/reg isn't charging correctly. I would suggest changing the charge system to a Delco self regulating alt. There is a special alternator housing to accomplish this. I've done the conversion serveral times with no regrets.
  • Posted 27 Jul 2012 08:38
  • By bbforks
  • joined 1 Mar'12 - 1,437 messages
  • Pennsylvania, United States
bbforks (at) Hotmail (dot) com
Customers love technology- until they have to pay to fix it!
Being this is an older truck,it might be possible that it has an external voltage regulator,might just need to change that if this is the case???
  • Posted 27 Jul 2012 08:10
  • By kevin_t
  • joined 2 Dec'10 - 1,301 messages
  • Pennsylvania, United States
Should get 14 volts while running,if alt. is putting out.Quick check ,Pull one of the battery cables off ,while engine is running.If it dies.Alt. isnt putting out.also,bearing at rear of alt. will magnitize,if its chargeing
  • Posted 27 Jul 2012 08:07
  • By kent_w
  • joined 5 Jan'12 - 102 messages
  • North Carolina, United States
The voltage while running was 8-10v. It starts up just fine.
  • Posted 27 Jul 2012 06:35
  • By rslaback
  • joined 25 Nov'09 - 7 messages
  • Wisconsin, United States
As Titus stated would also check the fan/alternator belt for proper tension,being an older truck isnt to many circuits that would drain the battery overnight,just lights(if it has them) and horn circuit.
Also check the cable from the alternator to the battery for corrosion and tighness of connections, and do a voltage drop on it,also check for corrosion at the battery terminals and do a voltage drop there also on both positive and negative cables. Check to make sure cables are not corroded internally,have seen cables that look fine on the outside but were full of green junk on the inside of the cable from copper corrosion.
  • Posted 27 Jul 2012 05:43
  • By kevin_t
  • joined 2 Dec'10 - 1,301 messages
  • Pennsylvania, United States
Sounds like a bad battery to me,if its dropping to 8.5v while cranking then i suspect the battery. Did you put a meter on the battery while its running to see what the voltage is then??
  • Posted 27 Jul 2012 05:34
  • By kevin_t
  • joined 2 Dec'10 - 1,301 messages
  • Pennsylvania, United States
Check the fan belt, charge battery do a heavy discharge test should stay above 10 volts if not possible battery failure try a different battery and check charging rate 14 to14.5 volts required. If you have correct charging rate check to see if any circuit is draining the battery.

Regards Titus
  • Posted 27 Jul 2012 03:53
  • By Titus
  • joined 6 Jul'10 - 185 messages
  • North Yorkshire, United Kingdom

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