Charging question

[xr4tifan]

Why does my "charging" indicator (battery symbol) not go off until I've hit 2,000 RPMs or so? Is this normal?

[Ed Lijewski]

A surmise: the regulator/rectifier brushes are worn and making poor contact with the commutator/and or the vcommutator is worn/dirty. Regulators are easy to R&R. (I have a new in-box one for $35 shipped.)

YMMV

[ford.scorpio]

x2; worn out brushes

FYI & for the future references, if your charging light does not come on when you turn on the key (lose connection or burned out bulb), alternator WON"T be charging......

[xr4tifan]

Revising this thread. I replaced the alternator with a new/reman one and I'm still having to rev the engine to get the charging indicator to shut off. (Even the old one had brushes making good contact.) Checked all electrical connections from battery to alternator and all are good. Is there anything else that could cause this problem?

[John Brennan]

As I recall, my '85 did that all the time. There were never any deleterious effects I could tie it to; I assumed it was normal.

[brokencase]

This happened to me when I replaced my dash lights with LEDs.

The warning light for the alternator depends on the current rating of the original incandescent bulb.
When I put the LED in it did not draw as much current. Had to rev to 2-3 grand to get the light to go out.

I pulled the cluster and put an original bulb back in for the alternator warning light.

[Ed Lijewski]

The remanufacturer, if a quality firm, should have a tech office or customer service number. I had an electrical charging system anomaly and spoke with a tech of the firm who walked me through several live questions and testing results relating to measurement of voltage/continuity/ground of the alternator at rest and spinning.

YMMV

[Mike McCreight]

Normal on the early cars.
Start the car, wait a bit, blip the throttle.
Repeat.

[Ed Lijewski]

XRs?. Dunno.

Scorpios? Don't think so.

YMMV

[Ed Lijewski]

Something to check is the small wire from the harness to the back of the alternator-it provides the necessary "excitor" current to start charging by the alternator. Wire should good; clip on connector shoukd be firmly attached to the wire; connector should firmly attach to alternator male prong.

YMMV

[Mike McCreight]

XRs?. Dunno.

Scorpios? Don't think so.

YMMV

Oops.
My bad.

[John Brennan]

XRs?. Dunno.

Scorpios? Don't think so.

YMMV

Oops.
My bad.

I considered this as well, but I figured, same manufacturer, same time period, might be the same of very similar arrangement.

[Ed Lijewski]

Often not well known is that alternators do not produce voltage/current as soon as they start to spin. There is a zero-ampere speed at which the alternator reaches its rated voltage before it can generate any current. This is typically 1000-1100 engine rpm on Merkur alternators (alternator rpm is higher as its pulley is smaller than the crank pulley). At idling speed (OEM settings) the alternator has to satisfy basic electrical demands without running down the battery.

Just above the idle speed is the cut-in speed at which the alternator begins to deliver current for the first time. The exact speed depends on the battery voltage, voltage from the alternator warning light (pre-excitation power), the rate of change of rotational-speed and the magnetic remanence of the rotor's magnets.

If the alternator cut-in speed is consistently far above ~ 1100 rpm that suggests an anomaly sonewhere in: the battery, the excitation circuit, the voltage regulator, and/or the alternator itself.

Brush off (intentional irony) concern about that high cut-in speed if you so choose; but understand that it is not normal.

YMMV

[brokencase]

I disagree Ed, For a couple of reasons...

Once started, a Scorpio will run and idle just fine with the battery disconnected.
Don't ask me how I know...

I have a voltmeter that plugs into the cigarette lighter socket...like one of these..
http://tinyurl.com/zuygetb
Best $2 spent, BTW!

A Scorpio alternator is putting out around 13.4 volts at idle with no accessories turned on.

It won't vary much with RPM. But it will drop a little depending on load.
Of course we are not measuring current here, just voltage.

The above being said, it should be mentioned that it is not that great. It's adequate
but not great.

If I plug the volt meter into my 03 Sport Trac I typically get above 14 volts at idle
and it is more solid.

It's a known fact that the regulator is not that good on the Bosch 90 amp unit.
This link shows what others have done about it.
http://www.turbobricks.com/mods.php?content=art0004

I'm not ready to go to that effort yet. But I might.
Right now my alternator (@75k miles) has the original Bosch brush/regulator module.
I bought an aftermarket replacement and I am hoping the solid state is a
better & more modern design. I'll put it in this coming summer.

[Ed Lijewski]

^^ Didn't address charging system theory/principles...nor suggest an answer to the Poster's question.
I have a couple of those ~$2.50 cigar lighter voltmeters, they're useful only for fuzzy snapshots of voltage. As they measure voltage at the cigar lighter, readings are subject to voltage drop. The post above doesn't address charging system theory/principles...nor suggest an answer to the Poster's question.

I have a couple of those ~$2.50 cigar lighter voltmeters, they're useful only for fuzzy snapshots of voltage. As they measure voltage at the cigar lighter their readings are subject to voltage drop.

A direct connection voltmeter-battery is best.

Idling, with a new alternator:



Voltage regulator P/Ns for Scorpio and XR are the same.

Disconnecting battery cable(s) while engine is running is a first principle disqualification for offering charging system advice.

YMMV