Masters degree credit available for alternator charging question

[hippieforever3]

I'm posting this here rather than the FC forum bcause it may be a
generic issue across models.

I've looked a few diffent versions of the charging / starting
schematics and can't find anything that explains what I'm seeing.

Consider this sequence;
1. Turn on master power switch in the battery compartment
2. Observation - dash voltage is showing 12+ to 13V, no current
3. Turn ignition key
4. Observation - dash voltage momentarily drops to 10.5V
5. Engine starts
6. Observation - Dash voltage rebounds to approx. 11.5V, no current
7. Momentary tap on the throttle, approx. 1500rpm or more
8. Observation - Dash current now showing +50a to 100a, voltage starts
to climb toward 13-14 volts

It's steps 6 - 8 that mystify me. I can understand the voltage
rebounding after the starter surge but why no current before revving
the engine?

This implies a relay somewhere that only kickes in after a little rpm
rev. I don't see it on any of the various BB schematics I've got. Is
there an internal relay in the alternator?

Has anyone else seen this or do I have some "custom" configuration?

Movin on,
GPSGary
1984FC35

[sfedeli3]

Gary,

You had to spin-up the original Motorola and Delco-Remy alternators
to pull-in/excite the field. If you get a new/used Leece-Neville
alternator, you will see an immediate charge (self-exciting). My coach
had the same behavior when I would first power up. Usually, I would
not see any charge until I hit the highway and got the revs up over
2000, then the amps would peg-out at 150 or so for a while and slowly
come back down to 50 or so. My new Leece-Neville shows a 14.2 volt
charge at 50 amps as soon as the engine spins over and starts. The
amps slowly drop back as the batteries get topped off again.

Shane Fedeli
85PT40
Hershey, PA

. --- In WanderlodgeForum@yahoogroups.com, "hippieforever3"
wrote:
>
> I'm posting this here rather than the FC forum bcause it may be a
> generic issue across models.
>
> I've looked a few diffent versions of the charging / starting
> schematics and can't find anything that explains what I'm seeing.
>
> Consider this sequence;
> 1. Turn on master power switch in the battery compartment
> 2. Observation - dash voltage is showing 12+ to 13V, no current
> 3. Turn ignition key
> 4. Observation - dash voltage momentarily drops to 10.5V
> 5. Engine starts
> 6. Observation - Dash voltage rebounds to approx. 11.5V, no current
> 7. Momentary tap on the throttle, approx. 1500rpm or more
> 8. Observation - Dash current now showing +50a to 100a, voltage starts
> to climb toward 13-14 volts
>
> It's steps 6 - 8 that mystify me. I can understand the voltage
> rebounding after the starter surge but why no current before revving
> the engine?
>
> This implies a relay somewhere that only kickes in after a little rpm
> rev. I don't see it on any of the various BB schematics I've got. Is
> there an internal relay in the alternator?
>
> Has anyone else seen this or do I have some "custom" configuration?
>
> Movin on,
> GPSGary
> 1984FC35
>

[Richard Gideon]

I agree with Shane's posting...also, do not overlook a mechanical
issue such a loose set of alternator belts. If the belts are worn
out or slipping badly they need to be replaced. Most difficult to
diagnose from afar. Sign up and attend one of the many rallies held
across the country...some of us are starved to get 'hands on'
troubleshooting experience! Sounds like your batteries are quite
undercharged...upgrade those obsolete battery boilers if you you have
not changed them yet.

Dick Gideon
1989 35FC
Rolla, MO

--- In WanderlodgeForum@yahoogroups.com, "hippieforever3"
wrote:
>
> I'm posting this here rather than the FC forum bcause it may be a
> generic issue across models.
>
> I've looked a few diffent versions of the charging / starting
> schematics and can't find anything that explains what I'm seeing.
>
> Consider this sequence;
> 1. Turn on master power switch in the battery compartment
> 2. Observation - dash voltage is showing 12+ to 13V, no current
> 3. Turn ignition key
> 4. Observation - dash voltage momentarily drops to 10.5V
> 5. Engine starts
> 6. Observation - Dash voltage rebounds to approx. 11.5V, no current
> 7. Momentary tap on the throttle, approx. 1500rpm or more
> 8. Observation - Dash current now showing +50a to 100a, voltage
starts
> to climb toward 13-14 volts
>
> It's steps 6 - 8 that mystify me. I can understand the voltage
> rebounding after the starter surge but why no current before
revving
> the engine?
>
> This implies a relay somewhere that only kickes in after a little
rpm
> rev. I don't see it on any of the various BB schematics I've got.
Is
> there an internal relay in the alternator?
>
> Has anyone else seen this or do I have some "custom" configuration?
>
> Movin on,
> GPSGary
> 1984FC35
>

[Pete Masterson]

It may simply reflect the engine alternator not able to put out significant amps at low idle speed -- or the voltage regulator is failing to 'kick in' until revs are up a bit. The controlling device is the voltage regulator associated with the alternator.

Some alternators have internal voltage regulators and others have external regulators. I'll leave it to someone with a model more contemporary to yours to comment on what's likely on your FC. Keep in mind, a previous owner may have replaced the alternator (and voltage regulator) at some point, making yours no longer match the OEM arrangement.

It is unlikely, but if you have a sophisticated inverter/charger control module (such as the Heart Link 2000 R as installed (after market) in my coach) the charging from the alternator would be controlled by that device instead of the normal regulator.

Pete Masterson

'95 Blue Bird Wanderlodge WBDA 42

"aeonix1@mac.com"

On the road at Lockhart, TX.

On Nov 14, 2008, at 1:56 PM, hippieforever3 wrote:

I'm posting this here rather than the FC forum bcause it may be a 

generic issue across models.

I've looked a few diffent versions of the charging / starting 

schematics and can't find anything that explains what I'm seeing.

Consider this sequence;

1. Turn on master power switch in the battery compartment

2. Observation - dash voltage is showing 12+ to 13V, no current

3. Turn ignition key

4. Observation - dash voltage momentarily drops to 10.5V

5. Engine starts

6. Observation - Dash voltage rebounds to approx. 11.5V, no current

7. Momentary tap on the throttle, approx. 1500rpm or more

8. Observation - Dash current now showing +50a to 100a, voltage starts 

to climb toward 13-14 volts

It's steps 6 - 8 that mystify me. I can understand the voltage 

rebounding after the starter surge but why no current before revving 

the engine?

This implies a relay somewhere that only kickes in after a little rpm 

rev. I don't see it on any of the various BB schematics I've got. Is 

there an internal relay in the alternator?

Has anyone else seen this or do I have some "custom" configuration?

Movin on,

GPSGary

1984FC35

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