Alternator testing & troubleshooting

[Snuffy "Hub Cap" McKinney]

My 97 Ford van has an intermittent electrical problem. Testing the battery under load it seems to be OK. Connections and wires are all good. Now I suspect the alternator.

It's a job to R/R the alternator in this car, so I'll really like to confirm that's the problem first. Simple checks shows it's charging and battery holding a charge, but that's when it's not acting up.

Anyone know where to find a schematic of the alternate? Or a way to get it to show the problem? Most of the time, no symptoms.

This is typically of the intermittent problem.....

At night, with the headlights on, the lights and meter start to cycle very slightly about 2 Hz. One night I had parked and left the lights on for 20 minutes, then started the car and the battery warning light started flashing and the meter needle swinging 0-100% back and forth indicating a problem. I switched to parking light and about 5 minutes later all returned to normal.

Thanks!

[jurb...@gmail.com]

With the car running it should have at the very least 14 volts at the battery terminals. Actually 15 volts is better and I like to see 15.5, moreso for people who are in the north and drive in the dark.

You also need to know if there is an abnormal load draining the battery. This is shown by taking off one battery terminal and connecting a taillight bulb, or other 12 volt bulb to connect it.

[jurb...@gmail.com]

Also check and/or clean ALL connections between the alternators, battery and starter.

[ohg...@gmail.com]

I don't remember the years affected, but Fords did have a problem with the connector plug on the alternator. If you can get to it, wiggle it while the engine's running and see if there's any affect.

Modern cars (yours included) are real picky about battery damping. I've seen bad batteries cause weird problems yet still deliver enough current to spin the starter. If you have a bad diode in the alternator it can cause an AC component which drives electronics nuts. If the alternator is original it's 20 years old, so it could be dying.

And as jurb pointed out, check those battery connections first and thoroughly. My wife's Jeep had an intermittent problem that wasn't solved until I cut off the old battery terminals and installed clamp on ones. When that was acting up, it would peg all the gauges and flash trouble lights.

[Bruce Esquibel]

"Snuffy \"Hub Cap\" McKinney" <Snuffy-...@livebait-mckinney.com> wrote:

> At night, with the headlights on, the lights and meter start to cycle very
> slightly about 2 Hz. One night I had parked and left the lights on for 20
> minutes, then started the car and the battery warning light started
> flashing and the meter needle swinging 0-100% back and forth indicating a
> problem. I switched to parking light and about 5 minutes later all
> returned to normal.

I don't have any answers to your questions but an opinion based on owning a
1997 Lincoln.

Replace the alternator and be done with the problem.

On my car it has both an idiot light and a message system which is supposed
to display "check charging system" when something goes wrong.

In the almost 20 years I owned that thing, neither have been of any help
with nearly dead batteries or failing alternators. The way I figure it, I
don't think either do anything unless you wrap the car around a light post
going 90 mph. Even then, the message center may only report to "check wiper
fluid level".

As far as I can determine, both gauges are connected to the alternator
itself, like a "go no/go" feed or sense lead. It doesn't read or care what
the voltage is, or what the amps are being produced. The alternator itself
has to be able to figure out something is wrong and be able to send the
message.

It just doesn't work.

I don't know how many times I've read on the car owners message board for
that model asking if it's normal that the alternator failed going 60 on an
expressway when the battery ran out of juice (car dies and stalls) with no
previous warning.

Your "gauge" showing 0-100% is a tipoff it's the same or similar system to
mine. 0-100% of what exactly? Volts? Amps? Volt/Amps? That gauge is the same
as my message center for "check charging system" (which never comes on).

Since the alternator is the only thing that can trigger the warning, it's
the alternator itself that is the problem. I'm pretty sure Ford used that in
the late 1990's, as some kind of self-diagnosting, early warning alternator
that came out brain dead instead.

If the lights are flickering, gauges going back and forth from 0 to 100,
just replace the alternator. It's not going to be anything else.

-bruce
b...@ripco.com

[pf...@aol.com]

On Monday, May 23, 2016 at 7:47:00 AM UTC-4, Bruce Esquibel wrote:

>
> Replace the alternator and be done with the problem.
>

Agreed. And as it is a "job", replace any weak links between the alternator and the rest of the vehicles. Check all connectors, and tighten them up and lubricate them with the appropriate dielectric silicon grease to prevent corrosion - and, again, be done with it!

Peter Wieck
Melrose Park, PA

[et...@whidbey.com]

I have seen this exact behavior occur because of a bad ground. I also
had a similar problem on my backhoe and it was a bad regulator. Inside
the regulator a wire had come loose and was making an intermittent
connection. So sometimes the charging worked and other times it
wouldn't.
Eric

[Dave M]

--

Having the meter slam back & forth like that indicates a loose wire or fuse
connection in the charging circuit. Couldn't blame it solidly on the
alternator, but it's in the circuit, so it's certainly a prime suspect.
Also suspect is the "megafuse", most likely located in a fusebox somewhere
under the hood. If the fuse is OK, be sure to look at the socket that it
plugs into. If the contacts are burned or overheated, that's your first
repair. The element inside a fuse can break rather than blow. Look closely
at it with a magnifying glass to be sure.
Check your local auto parts stores (Autozone/O'Reilly's/Pep Boys/etc); some
might test your alternator at no charge.

Lots of info and wiring diagrams at http://tinyurl.com/zrzfn8m.
Good luck with your van.
Dave M

[Snuffy "Hub Cap" McKinney]

> > This is an intermittent problem that only happens when driving with the headlights on -- but does happen every time. Any ideas how to troubleshoot it?
> >
> > For awhile the needle would oscillation between the normal 50-60% position a few degrees after driving a half hour or more with the headlights on. Then I cleaned all the connections in the starting systems from battery terminal to hot connections and grounds, and the problem stopped.
> >
> > Then last week, I had driven to a store at dusk with the lights on - no problem indicated. I left the lights on for 20 minutes while in the store. Then when I started, the battery needle start oscillating from 50% to 100% regularly, and the battery warning light started blinking off and on.
> >
> > Car was running fine so I turned off the headlights and just put on the parking lights so I could drive the 2 miles home. After driving about 1/2 mile the oscillating and flashing stopped.
> >
> > I have tried to duplicate the problem so I could show a mechanic, but all is back to normal for now.
> >
> > Without knowing anything, I would guest that the computer detected some kind of low voltage and the swinging and flashing was an attention-getter, and not the actual reading.
> >
> > Any ideas how to troubleshoot this?
> >
> >
> >
>
> Leaving the lights on 20 minutes would put more load on the alternator
> when you did start the car. The first thing that comes to mind is that
> for some reason the alternator is unable to work properly under high load.
>
> The second thing that comes to mind is some serious sounding problems
> have simple solutions. Higher load makes the alternator work harder.
> It can be something as simple as a slipping belt. I'd tighten or
> replace it before rebuilding the alternator. Yes, I've seen it happen
> more than once. .
---

Thanks for all the help. Still trying to find the time to spend TS...

Last night I was able to catch it cycling just now. No time to check at the alternator tonight, but here's some voltages at the battery terminal.... Turn signals seems to cause the cycling tonight, although I have seen it cycling with just the lights on.

Battery with engine off - 13.6
Turned engine on
Idling with no lights - 15.0 steady
Turned on parking lights - 15.0 steady
Turned on headlights - 15.0 steady
Turned on headlights and turn signal - 15.2-15.8 cycling
No lights, turn signal on - 15.2-15.8 cycling

[Sjouke Burry]

That sounds like a defective regulator or generator
going on/off.
Which would suggest the two voltages.
Bad wiring would produce a different pattern.

[jurb...@gmail.com]

>"Battery with engine off - 13.6
>Turned engine on
>Idling with no lights - 15.0 steady
>Turned on parking lights - 15.0 steady
>Turned on headlights - 15.0 steady
>Turned on headlights and turn signal - 15.2-15.8 cycling
>No lights, turn signal on - 15.2-15.8 cycling "

Does not sound to me like you need an alternator. As much as old timers may disagree, 15 volts it just about where you want it. These newer batteries can take it. To charge the old batteries of the 1960s that hard would cause too much water loss and you'd have to feed it every couple of day. Not no mo.

If you are charging at or near 15 volts and have trouble starting or anything you either have a bad battery or a fault in the system draining the battery. And don't forget, newer cars do drain the battery constantly to maintain memory.