• TomB
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  • From: Austin, TX
  • Registered: 2004-03-27
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Topic: Alternator Voltage Regulator Specs

As I noted under the "Battery Keeps Dying" post I had installed a VDO volt meter and found my alternator output dropped considerably under load, from about 13.5 V to about 12.5 V with headlights on. It looked to me like poor load regulation on the voltage regulator.
Well, before taking action I happened to review the VW dealer tech microfiche for the T1 charging systems, and found test specs for both the older alternator with external regulator (under the rear seat) and the later (primarily Bosch) alternator with internal regulator. Guess what: the spec for the internal regulator version allow more voltage droop than the older type. The external regulator specs are for voltage under full load to be 13.9 to 14.8 V; but the internal regulator version specs are 12.5 V to 14.5 V at load.
So it looks like the design of the internal regulator really doesn't handle load as well. Time to find those instructions for converting to external regulator!

  • From: somewhere over the rainbow USA
  • Registered: 2006-07-26
  • Posts: 1,889

Re: Alternator Voltage Regulator Specs

TomB,
  That is interesting to know. I would like to see how to convert to external VR. I have seen directions to go the other way but never from internal to external VR. link?
burrhead

burrhead

A wise man makes his own decisions, an ignorant man follows public opinion.
  • From: B.C.Canada
  • Registered: 2005-01-26
  • Posts: 2,610

Re: Alternator Voltage Regulator Specs

Perhaps 12.5 V. is enough for charging the battery and more is excessive? It is amperage after all that's needed to drive more accessories. All accessories are designed for 12 V so do you want more? I wouldn't be too quick to second guess the German engineers. Been down that road.

Jim

'71 SB(DD only 79K(now 84K miles) & '78 FI Westy (project)
PO of '65 Beetle in '69, '70 Crewcab & '70 Ghia in '77
'71 Super inside rear vents now available
http://www.openroad.ca/volkswebbin/view … p?id=85915
  • Ryan
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  • From: Silicon Valley
  • Registered: 2004-04-24
  • Posts: 587

Re: Alternator Voltage Regulator Specs

If memory serves you need at least 12.7 to put a decent charge on the battery.  You might be surprised to hear this, but not ALL accessories are designed for 12 volts.  The are designed to 'work' with 12 volts, but many things prefer upwards of 14 volts to be really happy.  My stereo head unit will kick down the internal amp output for less than 14 volts, all the ratings on my MSD are spec'd at 14 volts, and the list could go on.
Last I heard the current line of Bosch Alt w/ internal regulators are spec'd at 13.7 volts.  That said, I use a modified internal regulator from a Volvo that is set to 14.4 volts.  The footprint was the same, just needed to mod the leads.  Luckily I have a local shop that does rebuilds and they let me browse through their books to find what I wanted.  I brought it to them and they did a 'full' test (factory certified rebuild) and replaced the regulator for $30 total.
Anyways, my point.  You might want to look into a different internal regulator first, they are very easy to replace and it'll look cleaner.  --Ryan

  • TomB
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Re: Alternator Voltage Regulator Specs

Thanks for the tip Ryan, sounds like a good mod. Do you have the part number for that Volvo regulator?

  • From: Northern Illinois
  • Registered: 2004-03-27
  • Posts: 1,105

Re: Alternator Voltage Regulator Specs

Ryan,
I'd be interested in the Volvo VR as well. My Mexi is doing the same as Tom's and come spring I want to fix it. I was considering installing a 75a alternator since I have A/C as well but the VR is a hell of a lot easier to change.

-Darby
  • From: Northern Illinois
  • Registered: 2004-03-27
  • Posts: 1,105

Re: Alternator Voltage Regulator Specs

Tom, Here's what I saved from the Mexi files:


How to change the voltage regulator on a beetle with the alternator in
place. The result is an external regulator:
1. Remove the air filter holder.
2. Remove the D+ spade connection (blue wire) on top of the
alternator.
3. Carefully remove the black cover with three screws marked "D+"
located on top of the alternator.
4. The black cover that was removed is also the brush assembly.
5. You will see a green and red wire going to a spade connection.
Using needle nose pliers twist and remove the green and red wires from
the old voltage regulator inside the alternator.
6. Drill two holes on top of the black brush assembly you just removed
marked D+.
7. Insert the green and red wires through the holes and re-attach them
to there proper spade locations on the brush assembly. (Note: the
spade sizes are different and you cannot make a mistake here.)
8. With the new voltage regulator in hand, solder the green wire to
the green and red wire to the red. I would recommend using shrink
tubing to insulate the exposed parts of the wire.
9. Located behind the body of the new voltage regulator,solder a 5
inch black #10 wire to the silver metal through hole. This will be the
ground cable.
10. Carefully re-install the black brush assembly using the 3 screws.
11. Install a #10 lug on to the other side of your ground cable.
12. Secure the lug using the screw and washer located on top of the
alternator next to the D+ cover.
13. Find a convenient location and secure the voltage regulator body
using a tie wrap.
14. Re-install the blue wire with the spade connector to the D+.
15. Re-install the air filter holder.
16. Voltage Regulator: part number 9-190-087-003.

I'm not sure about the part number given here though, attached is a link to CIP1 that shows a picture, isn't this the original Brazil regulator ??
http://www.cip1.ca/SearchResults.asp?Se … arch2.y=13

Last edited by DrDarby (2008-02-12 18:51:30)

-Darby
  • Ryan
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  • From: Silicon Valley
  • Registered: 2004-04-24
  • Posts: 587

Re: Alternator Voltage Regulator Specs

Not ignoring you guys, I'm looking.  I did this so long ago I really don't remember off hand, but I'm looking.  --Ryan