12SI alternator troublshooting: DOH: the ignominious denoument

I had already reassembled the 12SI when most of the discussion here
took place. Saturday morning I decided to reinstall it into the car.

First, I checked and the tan/brown wire had zippo voltage on it with
the key off. Then I installed the alternator and the same problem:
increased current draw with the two-pin connector.

THEN I had the horrible realization.

In mid-December, my battery went bad. It was old, and one of the side
terminals had leaked and corroded the connection. I also made sure
that the aged wiring to the alternator was corrosion-free.

To clean the regulator connections, I popped the wires and connectors
from the plastic body, doused them with contact cleaner, and replaced
them.

You can probably see this coming: when reinserting the wires into the
plastic connector, I swapped 1 and 2. This results with relatively
normal alternator operation, except for a higher key-off drain. I
switched the wires to the way they're supposed to be, and now my key-
off draw is 10mA with the alternator all connected, and 9mA with the
two-pin pulled. A great improvement on the 300mA draw before. And the
alternator charged fine; no dead shorts to ground either.

So tomorrow I'll go to the auto electric places and get new bearings
pressed in, and also collect a proper 12SI rectifier bridge. Then
hopefully I can ignore this alternator for the likely remaining life
of the car.

Question though: how do you determine if there's excessive voltage
drop in the wiring? I turned on the blower on high and the back
defrost on. Trying to read the voltage between the battery and
alternator B+ terminal was frustrating, with the readins flipping all
around the 0.03V range, sometimes going up to 0.06 but sometimes going
a bit negative.

What I'm trying to figure out is why the alternator keeps the voltage
up when the car has recently been started, no matter if all the
accessories are on. After a while, the voltage will drop at idle with
a full electrical load. Is this just increased resistance in the
alternator when it gets hot?

.....Ed

On 1/18/2010 7:57 AM, Ed Treijs wrote:


>
> What I'm trying to figure out is why the alternator keeps the voltage
> up when the car has recently been started, no matter if all the
> accessories are on. After a while, the voltage will drop at idle with
> a full electrical load. Is this just increased resistance in the
> alternator when it gets hot?

Your regulator is well... regulating. It's normal for your voltage to go
up to 14V+ or so right after starting the battery. My assumption is that
starting puts a heavy drain on the battery which is then brought back up
to charge/voltage by the alternator. The battery voltage will drop back
down to 13.2V or so after a few seconds.

>
> .....Ed

On Jan 18, 3:04*pm, dsi1 > wrote:
> On 1/18/2010 7:57 AM, Ed Treijs wrote:
>
> > What I'm trying to figure out is why the alternator keeps the voltage
> > up when the car has recently been started, no matter if all the
> > accessories are on. After a while, the voltage will drop at idle with
> > a full electrical load. Is this just increased resistance in the
> > alternator when it gets hot?
>
> Your regulator is well... regulating. It's normal for your voltage to go
> up to 14V+ or so right after starting the battery. My assumption is that
> starting puts a heavy drain on the battery which is then brought back up
> to charge/voltage by the alternator. The battery voltage will drop back
> down to 13.2V or so after a few seconds.

Sorry, I wasn't being clear.

There is a decrease in overall voltage levels as everything warms up,
and the overall voltage levels are lower in summer than in winter. As
you say, that's to be expected from the regulator.

However, when the car is first started and is cold, say the (not-too-
accurate 1978-vintage) voltmeter shows 15.5V with no load. I turn on
the lights, heater blower, rear defrost, etc--I fully-load the
electrical system. The voltmeter continues to show 15.5V, maybe a
touch lower.

Let the engine warm up, and the voltmeter shows say 15.0V with no
load. (It consistently reads high. So did the gas gauge--so I ran out
of gas at 1/8 tank showing!) It'll stay at about 15.0 with a light
load, but once I put enough electrical accessories on, it'll drop to
14.0V or lower. For sure, rear defrost, blower motor, and headlights
on, it won't maintain voltage at idle or even at 1200 RPM.

Obviously fast idle with the choke on makes this comparison difficult,
but sometimes the motor will come off fast idle pretty quickly, and I
see this happening. It's almost like the alternator gets tired! Well,
hot, anyway.

.....Ed

On 1/18/2010 12:24 PM, Ed Treijs wrote:
> On Jan 18, 3:04 pm, > wrote:
>> On 1/18/2010 7:57 AM, Ed Treijs wrote:
>>
>>> What I'm trying to figure out is why the alternator keeps the voltage
>>> up when the car has recently been started, no matter if all the
>>> accessories are on. After a while, the voltage will drop at idle with
>>> a full electrical load. Is this just increased resistance in the
>>> alternator when it gets hot?
>>
>> Your regulator is well... regulating. It's normal for your voltage to go
>> up to 14V+ or so right after starting the battery. My assumption is that
>> starting puts a heavy drain on the battery which is then brought back up
>> to charge/voltage by the alternator. The battery voltage will drop back
>> down to 13.2V or so after a few seconds.
>
> Sorry, I wasn't being clear.
>
> There is a decrease in overall voltage levels as everything warms up,
> and the overall voltage levels are lower in summer than in winter. As
> you say, that's to be expected from the regulator.
>
> However, when the car is first started and is cold, say the (not-too-
> accurate 1978-vintage) voltmeter shows 15.5V with no load. I turn on
> the lights, heater blower, rear defrost, etc--I fully-load the
> electrical system. The voltmeter continues to show 15.5V, maybe a
> touch lower.
>
> Let the engine warm up, and the voltmeter shows say 15.0V with no
> load. (It consistently reads high. So did the gas gauge--so I ran out
> of gas at 1/8 tank showing!) It'll stay at about 15.0 with a light
> load, but once I put enough electrical accessories on, it'll drop to
> 14.0V or lower. For sure, rear defrost, blower motor, and headlights
> on, it won't maintain voltage at idle or even at 1200 RPM.

15.5V with no load seems awfully high - maybe your regulator is faulty?
I would think your battery would be damaged with voltages that high.

Anyway with a full load, it would seem normal if your voltage falls -
your alternator is not able to keep up with the load. I think that most
automotive charging systems are not designed to be able to handle all
the load that your car might throw at it under all conditions which is
one of the reasons for a battery. Anyway that sounds normal. Your
voltage regulation does not.


>
> Obviously fast idle with the choke on makes this comparison difficult,
> but sometimes the motor will come off fast idle pretty quickly, and I
> see this happening. It's almost like the alternator gets tired! Well,
> hot, anyway.
>
> .....Ed

On Jan 18, 8:22*pm, dsi1 > wrote:
> 15.5V with no load seems awfully high - maybe your regulator is faulty?
> I would think your battery would be damaged with voltages that high.

15.5V on the factory dash voltmeter corresponds to low-to-mid 14.xV
measured with a proper meter across the battery terminals (or alt B+
to ground). It doesn't help that the voltmeter is far to the right of
my line of sight, so parallax error probably adds half a volt, in
addition to its inherent inaccuracy. But that's how they made Trans
Ams in the 1970s.

I could come up with a correspondence table, and read it by leaning
over the transmission tunnel to avoid parallax error, but that sounds
like a lot of work. Anyway, I've checked that the system isn't
overcharging. But the way I see if the system is working "normally" is
to glance at the dash to see if the gauge is pointing to where I
expect it to.

I will however double-check cold and warm voltages once I reinstall
everything--I'm on the way to the electrical shop to get a new
rectifier bridge and bearings. Anyway, I have two regulators, both of
which are not obviously faulty.

.....Ed

On 1/19/2010 5:48 AM, Ed Treijs wrote:
> On Jan 18, 8:22 pm, > wrote:
>> 15.5V with no load seems awfully high - maybe your regulator is faulty?
>> I would think your battery would be damaged with voltages that high.
>
> 15.5V on the factory dash voltmeter corresponds to low-to-mid 14.xV
> measured with a proper meter across the battery terminals (or alt B+
> to ground). It doesn't help that the voltmeter is far to the right of
> my line of sight, so parallax error probably adds half a volt, in
> addition to its inherent inaccuracy. But that's how they made Trans
> Ams in the 1970s.

I like those old cars with the voltmeters. If you had an ampmeter like
my mom's old car, you'd see the needle swing to the plus side for a
short time while the battery was charging every time the engine was
started or you'd see the needle blip when the lights were turned on. Of
course, this gave some indication of what the voltage was doing.

My old 67 Barracuda had a big, vac gauge on the dash marked with ranges
for power and fuel economy. It was my favorite gauge of all time and
gave me an awareness of the most efficient technique of using the
accelerator pedal as well as engine problems. My least favorite was the
big single tach directly in front of the driver on an Alfa Romeo.

>
> I could come up with a correspondence table, and read it by leaning
> over the transmission tunnel to avoid parallax error, but that sounds
> like a lot of work. Anyway, I've checked that the system isn't
> overcharging. But the way I see if the system is working "normally" is
> to glance at the dash to see if the gauge is pointing to where I
> expect it to.
>
> I will however double-check cold and warm voltages once I reinstall
> everything--I'm on the way to the electrical shop to get a new
> rectifier bridge and bearings. Anyway, I have two regulators, both of
> which are not obviously faulty.

I'm used to digital read-out of voltages. You have to ignore the
markings on dash voltmeters and instead learn to read the normal range
travel but that's the way it's always been with these gauges.

>
> .....Ed

One of the fun things about working on cars is you go into shops that
are a bit of history.

I went to an auto electrical place. Big shop, full of parts and
assemblies and tools and meters. One really old guy (he said something
about being 80) sitting in the office, otherwise no activity. I said I
needed a rectifier bridge and I wanted new bearings. He wound up
giving me a preassembled 12SI end frame, including rectifier bridge,
new regulator and brushes, new bearing, new diode trio. And a drive
end bearing. All for $20. (If anyone in the Toronto area is
interesting, the shop is Starter King, on Lockport, off Shorncliffe,
south of Dundas.)

I did have to go back, because the drive end bearing he gave me was
the wrong size. Got the right one, and he showed me how to press it in
using the hand press. Much easier than my basement-wall-stud
destroying technique to press the old bearing out.

I won't get around to installing the re-rebuilt alternator until
Saturday. At least I know the bearings are good, and I really cleaned
up the slip rings. New electronic components--should work great. And
I've learned about alternator construction. All for $20. Can't beat
that.

On 1/19/2010 1:17 PM, Ed Treijs wrote:
> One of the fun things about working on cars is you go into shops that
> are a bit of history.
>
> I went to an auto electrical place. Big shop, full of parts and
> assemblies and tools and meters. One really old guy (he said something
> about being 80) sitting in the office, otherwise no activity. I said I
> needed a rectifier bridge and I wanted new bearings. He wound up
> giving me a preassembled 12SI end frame, including rectifier bridge,
> new regulator and brushes, new bearing, new diode trio. And a drive
> end bearing. All for $20. (If anyone in the Toronto area is
> interesting, the shop is Starter King, on Lockport, off Shorncliffe,
> south of Dundas.)
>
> I did have to go back, because the drive end bearing he gave me was
> the wrong size. Got the right one, and he showed me how to press it in
> using the hand press. Much easier than my basement-wall-stud
> destroying technique to press the old bearing out.
>
> I won't get around to installing the re-rebuilt alternator until
> Saturday. At least I know the bearings are good, and I really cleaned
> up the slip rings. New electronic components--should work great. And
> I've learned about alternator construction. All for $20. Can't beat
> that.

You sure can't. We had a shop called "Starters and Alternator" right
down our street and I loved that place. One time the guy rebuilt my
alternator (or was it a starter?) and another time he swapped me for one
on the shelf. Unfortunately, they moved away soon after. That's the breaks.

dsi1 wrote:
> On 1/19/2010 1:17 PM, Ed Treijs wrote:
>> One of the fun things about working on cars is you go into shops that
>> are a bit of history.
>>
>> I went to an auto electrical place. Big shop, full of parts and
>> assemblies and tools and meters. One really old guy (he said something
>> about being 80) sitting in the office, otherwise no activity. I said I
>> needed a rectifier bridge and I wanted new bearings. He wound up
>> giving me a preassembled 12SI end frame, including rectifier bridge,
>> new regulator and brushes, new bearing, new diode trio. And a drive
>> end bearing. All for $20. (If anyone in the Toronto area is
>> interesting, the shop is Starter King, on Lockport, off Shorncliffe,
>> south of Dundas.)
>>
>> I did have to go back, because the drive end bearing he gave me was
>> the wrong size. Got the right one, and he showed me how to press it in
>> using the hand press. Much easier than my basement-wall-stud
>> destroying technique to press the old bearing out.
>>
>> I won't get around to installing the re-rebuilt alternator until
>> Saturday. At least I know the bearings are good, and I really cleaned
>> up the slip rings. New electronic components--should work great. And
>> I've learned about alternator construction. All for $20. Can't beat
>> that.
>
> You sure can't. We had a shop called "Starters and Alternator" right
> down our street and I loved that place. One time the guy rebuilt my
> alternator (or was it a starter?) and another time he swapped me for one
> on the shelf. Unfortunately, they moved away soon after. That's the breaks.

I *so* wish I had a place like that around here. I need to get a VW
Corrado alternator rebuilt, and the only places I know that'd do it for
me are in Annapolis or Springfield. "ordering" a reman from the parts
store is approaching the value of the car.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

dsi1 wrote:
> On 1/19/2010 5:48 AM, Ed Treijs wrote:
>> On Jan 18, 8:22 pm, > wrote:
>>> 15.5V with no load seems awfully high - maybe your regulator is faulty?
>>> I would think your battery would be damaged with voltages that high.
>>
>> 15.5V on the factory dash voltmeter corresponds to low-to-mid 14.xV
>> measured with a proper meter across the battery terminals (or alt B+
>> to ground). It doesn't help that the voltmeter is far to the right of
>> my line of sight, so parallax error probably adds half a volt, in
>> addition to its inherent inaccuracy. But that's how they made Trans
>> Ams in the 1970s.
>
> I like those old cars with the voltmeters. If you had an ampmeter like
> my mom's old car, you'd see the needle swing to the plus side for a
> short time while the battery was charging every time the engine was
> started or you'd see the needle blip when the lights were turned on. Of
> course, this gave some indication of what the voltage was doing.
>
> My old 67 Barracuda had a big, vac gauge on the dash marked with ranges
> for power and fuel economy. It was my favorite gauge of all time and
> gave me an awareness of the most efficient technique of using the
> accelerator pedal as well as engine problems. My least favorite was the
> big single tach directly in front of the driver on an Alfa Romeo.
>

I like all of those gauges The tach front and center is nice for a
sports/racing car where you actually care more about how fast the engine
is turning than you are making sure you're not attracting the attention
of the po-po.

In my pickemup truck I swapped the gauge cluster for one with a tach,
and also hung a 3-gauge cluster under the dash with oil press (never
could get the stupid Ford "idiot gauge" to register properly, even after
following the instructions I found on the helping friendly interwebs)
vacuum and trans temp. I also have a tach strapped on the steering
column of my '55 Stude and have a vacuum gauge and voltmeter under the
dash. (it already had pretty good gauges stock; it has a 4-gauge multi
cluster thing with fuel, oil press, engine temp, and amps) One of these
days I'll rig up an oil temp gauge (that one's a 4-speed, so I need to
find a "useful" gauge to fill the empty hole. I already have all the
gauges I "need," but there's an empty hole in the add-on panel!)

The older a vehicle is, the more gauges I like to have. Makes me a
little more comfortable getting in it and driving long distances (or
through bad neighborhoods)

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel