Battery or alternator or other?

DrRadar · 08-30-2010, 10:40 PM

I can't figure out this puzzle. My son drives a 97 Ford Escort 2.0L with 123k. Last week, it died on him; first, the radio acted funny, then the speedometer quit working, the lights dimmed, and finally the engine stopped. There was not enough battery to turn it over. It jump started immediately and we charged from another vehicle for about five minutes, then tried to drive home. It went a few miles before it died the same way. Towed it home.

Charged the battery overnight; it accepted charge and charger shut off automatically like it does with a good battery. (With a bad battery, oftentimes the current won't decrease with charging time so the charger never shuts off.) A friend load-tested it and said the battery was ok. (The battery is two years old.) The alternator was replaced four months ago and is generating 14.2V at the positive battery post, which sounds good to me. Replaced the factory negative battery clamp with a "clamp-on" replacement. Drove it a day before it died again.

Pulled alternator; Autozone tested it and it passed. Suspected the factory connectors at the negative battery post for the electronics might be corroded inside the plastic, so cut them off, put on spade lugs, and connected to negative battery clamp.

Disconnected negative battery cable and measured resistance between alternator and battery - both the positive and ground connections. Both were 0.5 ohm or less. So I don't see a problem there. Charged battery again.

After a couple days of very light driving, it has died again. I suspect the battery, but am not sure. Specific gravity in all cells is about the same - just below the good/fair boundary - not bad for a discharged battery.

Any suggestions or advice before I roll the dice with a new battery?

Thanks.

danielsatur · 08-30-2010, 11:02 PM

How old is the battery? 2-years
It might not be holding a charge like it once did.

Some circuits might be connected to the battery fuse instead of a ignition fuse, a short causing the discharge.

inafogg · 08-30-2010, 11:41 PM

recharge battery and load test
fair to good like you said isnt good enough
can you check the cells indivisualy
sounds like a weak battery but thats my 2 cents

AzTumbleweed · 08-31-2010, 07:55 AM

A weak battery should not make it quit running if you have a good alternator. You have not said whether or not the BATTERY warning light is coming on. This might be a long shot but here's what I discovered on my Escort. The brushes in the alternator wore out. For some reason if it quits charging due to bad brushes the BATT warning light does NOT come on. Typically, it would charge when I started it up but quit charging after a few miles. The only way I knew this was that I have an after-market battery gage. If you have a volt meter I'd lengthen the leads so it would reach the inside of the car then go for a drive and watch the meter. If battery passed load test I'd rule that out but you might go to AutoZone for a second load test just to confirm it's good.

DrRadar · 08-31-2010, 08:38 AM

Quote:

Originally Posted by AzTumbleweed

A weak battery should not make it quit running if you have a good alternator.

That's why I'm puzzled. The car starts easily when jumped from another vehicle or with a freshly charged battery, but dies when running. Smells like an alternator, but haven't found a smoking gun to convince me.

Quote:

Originally Posted by AzTumbleweed

You have not said whether or not the BATTERY warning light is coming on.

The BATTERY warning light is not coming on - at least not when we're looking at it!

Quote:

Originally Posted by AzTumbleweed

This might be a long shot but here's what I discovered on my Escort. The brushes in the alternator wore out. For some reason if it quits charging due to bad brushes the BATT warning light does NOT come on. Typically, it would charge when I started it up but quit charging after a few miles. The only way I knew this was that I have an after-market battery gage. If you have a volt meter I'd lengthen the leads so it would reach the inside of the car then go for a drive and watch the meter.

This scenario fits the symptoms. I'll pursue this. But the alternator is only four months old; even with a reman from Autozone, the brushes should be new.

Quote:

Originally Posted by AzTumbleweed

If battery passed load test I'd rule that out but you might go to AutoZone for a second load test just to confirm it's good.

Easy enough to do.

Thanks for sharing your experience.

DrRadar · 08-31-2010, 08:40 AM

Quote:

Originally Posted by inafogg

recharge battery and load test
fair to good like you said isnt good enough
can you check the cells indivisualy
sounds like a weak battery but thats my 2 cents

I did check each cell, but after the battery was fully discharged. I'll recharge and retest.

DrRadar · 08-31-2010, 11:38 PM

First, a little administrative business. I posted two replies to this thread, but they aren't displayed when I select the thread from the Escort forum main page. They do show when "Printable Version" is selected. I don't know if I did something wrong. I don't want you to think I was ignoring your advice...

Per AzTumbleweed's suggestion, I ran a couple wires from the battery (recharged once again) to the cab and connected to multimeter. After starting the car, the meter showed 14.2V. But seconds after putting it into drive, the voltage dropped to 12.3V - lower than battery voltage with the car off. Apparently, an intermittent failure turned into a hard failure. I took the alternator back to Autozone and this time it failed their test. The replacement alternator is in the car and is generating about 13.8V.

The Autozone manager noted that the bad alternator had a Motorcraft regulator but the replacement has an after-market regulator. He said they were switching to the after-market regulators because of too many problems with the Motorcraft, and I must have gotten one of the few remaining alternators with Motorcraft regulators.

AzTumbleweed - Running wires to the cab was a very valuable tip and I appreciate that you took the time to share it.

Hopefully, this alternator lasts more than four months!

denisond3 · 09-01-2010, 07:14 AM

A couple of things I do for mine. I always clean the battery post and the inside of the battery terminal, brushing it lightly with the edge of a penknife blade or razor blade - to get the lead oxide off. That makes for a much better connection.
If either one of your battery terminals is one of the replacement kind that clamp on the end of the existing wire, they can result in a bad connection.
There are about 5 small wires that get grounded to a black connector at the negative terminal of the battery. Those have given me trouble on each of my 3 Escorts, and when they do I cut them off, strip the wires back, solder a thicker black wire to them, and bolt the other end of that single wire to the ground connection that is behind the battery and close to it - where the original heavy negative battery cable is bolted down.

zzyzzx2 · 09-14-2010, 08:27 AM

Quote:

Originally Posted by AzTumbleweed

A weak battery should not make it quit running if you have a good alternator. You have not said whether or not the BATTERY warning light is coming on. This might be a long shot but here's what I discovered on my Escort. The brushes in the alternator wore out. For some reason if it quits charging due to bad brushes the BATT warning light does NOT come on. Typically, it would charge when I started it up but quit charging after a few miles. The only way I knew this was that I have an after-market battery gage.

I can confirm the above statement. When the brushes go, the dash light does not come on and it charges intermittently for a while (several days). I do have a voltmeter installed in my dash.

zzyzzx2 · 09-14-2010, 08:29 AM

Quote:

Originally Posted by DrRadar

The Autozone manager noted that the bad alternator had a Motorcraft regulator but the replacement has an after-market regulator. He said they were switching to the after-market regulators because of too many problems with the Motorcraft, and I must have gotten one of the few remaining alternators with Motorcraft regulators.

Hopefully, this alternator lasts more than four months!

If it's a rebuilt one from Autozone/Advance Auto/PepBoys, or some similiar place, you'll be lucky if you can make it out of your driveway! That and I don't believe the store managers BS about Motorcraft voltage regulators.

AzTumbleweed · 09-14-2010, 12:44 PM

When my brushes went bad it would charge when I first started the car but would quit after a minute or two. THE RED WARNING LIGHT WILL NOT COME ON. The only reason I knew was because I installed a battery gage I found at a yard sale for $1 :-)

old_master · 09-14-2010, 05:24 PM

You mentioned the alternator was charging at 14.2 volts which means the voltage regulator is working. Don't believe the Autozone managers BS. A more likely scenario is the rectifier bridge in the alternator has a problem with one or more of the diodes. The voltage regulator will keep voltage where it should be but amperage output could be almost nonexistant with a bad diode. Autozone's alternator tester didn't find the problem the first time, you're lucky it caught it this time! Can't trust the manager, can't trust their equipment, and can't trust their parts.... what's left?

Intuit · 09-16-2010, 10:14 PM

I was thinking similar... that the AutoZone clerk/manager/whatever is incorrect. But it's not unusual for autoparts store clerks, some mechanics and computer techs to pull things from their rear-end.

As the brushes reached end of their life-span (at ~240k) i began to get a very faint battery light as the voltage reached a little above 10v. Engine still ran at the voltage but had an extremely low idle. Still running on the original Motorcraft alternator ~250k. '94 sedan 5-speed manual

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