Alternator testing & troubleshooting

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.

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

On Sunday, May 22, 2016 at 4:19:36 PM UTC-4, Snuffy "Hub Cap" McKinney wrot e:

ry under load it seems to be OK. Connections and wires are all good. Now I suspect the alternator.

irm that's the problem first. Simple checks shows it's charging and batter y holding a charge, but that's when it's not acting up.

it to show the problem? Most of the time, no symptoms.

y 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 fla shing and the meter needle swinging 0-100% back and forth indicating a prob lem. I switched to parking light and about 5 minutes later all returned t o normal.

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 th e engine's running and see if there's any affect.

Modern cars (yours included) are real picky about battery damping. I've see n bad batteries cause weird problems yet still deliver enough current to sp in 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 thorough ly. My wife's Jeep had an intermittent problem that wasn't solved until I c ut off the old battery terminals and installed clamp on ones. When that wa s acting up, it would peg all the gauges and flash trouble lights.

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 snipped-for-privacy@ripco.com

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

Peter Wieck Melrose Park, PA

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

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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

the headlights on -- but does happen every time. Any ideas how to troubleshoot it?

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.

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.

the parking lights so I could drive the 2 miles home. After driving about 1/2 mile the oscillating and flashing stopped.

but all is back to normal for now.

some kind of low voltage and the swinging and flashing was an attention-getter, and not the actual reading.

that

load.

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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

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

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 anythi ng you either have a bad battery or a fault in the system draining the batt ery. And don't forget, newer cars do drain the battery constantly to mainta in memory.