Author Topic: Not Charging Light is on, and "it's not charging"  (Read 4433 times)

Ross Parker

  • Guest
Not Charging Light is on, and "it's not charging"
« on: June 17, 2015, 14:00:17 »
Hi everyone....I could use some help. I've checked the previous threads and can't find what I'm looking for.
Bottom line is: where is the voltage regulator on my '68 280SL, US model, auto trans?
Here's the background...
-everything was fine, until the battery went dead because there was a big dead short.
-fixed the short, replaced the battery.
-in the process of replacing the battery, I inadvertently shorted the hot and ground on the little terminal block that sits on the front of the oil pan.
-car starts fine, but now "battery not charging" light is hard on...and it's true, it's not charging.
-when engine is running, and I remove the grounding wire off the battery, engine instantly stops.
-all fuses in the firewall panel are fine.
-took alternator off the car, had it bench tested. It is working fine.
-I believe alternator is original. The 'alternator bench test' guy said "you've got an external voltage regulator on that car. Check it"
So, I can't find another 'in-line' fuse in the charging circuit, and I can't identify the voltage regulator to check it out...maybe I fried it with that momentary "shorted at the little terminal block".
Any help in pointing me would be appreciated......Ross

Jonny B

  • Pagoda SL Board
  • Platinum
  • ******
  • USA, CA, San Marcos
  • Posts: 4198
Re: Not Charging Light is on, and "it's not charging"
« Reply #1 on: June 17, 2015, 14:24:47 »
Voltage regulator is mounted on the inner passenger side of the engine bay. It is a small metal box and should have a band of yellow tape around it. I am traveling this week and am not able to post a photo.

I replaced the alternator in my 250 SL a couple of years ago due to a short, and when we purchased the new alternator, we also got the recommended solid state replacement regulator.

Jonny B
1967 250 SL Auto, DB 568
1970 280 SL Auto, DB 904
1966 Morris Mini Minor

ja17

  • Full Member
  • Platinum
  • ******
  • USA, OH, Blacklick
  • Posts: 7414
Re: Not Charging Light is on, and "it's not charging"
« Reply #2 on: June 17, 2015, 14:31:38 »
The voltage regulator is the silver box on the left side of the engine compartment. It is near the left shock tower. It has a three-pronged plug hooked to the bottom of it.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1982 300TD Wagon turbo 4spd.
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

Ross Parker

  • Guest
Re: Not Charging Light is on, and "it's not charging"
« Reply #3 on: June 30, 2015, 12:41:26 »
Thanks everybody.....FIXED !!
It was the voltage regulator !!
The "alternator bench test" guy, tested the regulator (which was original) and said "it's not working properly, and, it gets hot"
I took it apart, and it seemed ok, except for a slight build up on one side of the points.
I decided not to file it down, but rather to get a new voltage regulator.
NOS on E-Bay $110 usd, sourced in USA.....likely 3 weeks away.
Parts supplier near my home found a new one (not OS) in Calgary supplier's warehouse.....$70 cdn, here in 3 days !
Installed it (same style of wiring connection plug) and alternator.
Connected battery, and fired it up !!
No flippin idiot light !
Wahoo....just in time for the July 1 Car Show tomorrow!!
Thanks again....this is a great Forum site !! ;D

Ross Parker

  • Guest
Re: Not Charging Light is on, and "it's not charging"
« Reply #4 on: June 30, 2015, 21:42:04 »
....oh, in case yer interested....the $60cdn voltage regulator that solved the problem, and had the perfect line up of plug connectors and bolt holes to the fender, was from Intermotor, VR 124....Ross