The truck started fine Sunday afternoon even after a very cold (4F) morning low. I let it warm up then headed on the 30 mile drive to the airport for a business trip. About 10 minutes into the drive, I watched the voltmeter on the dash drop to L and return to normal a few times. Then about 5 minutes later, it went to L and stayed. The check battery light was faint and fluttering but never solid on. I turned off all the electrics, but no change and the voltmeter stayed at L. At the park place, I left it running so as to avoid a possible jump start for the valet boys and I wasn't able to test to see if it would restart.

So I will have to deal with this when I return Friday. I expect a jump start will be needed at the park place. And I suppose the plan will be to take it to a AZ to get a alternator output test but since the check battery light never came on, I don't think there is a problem there. I believe it is the original battery so would not be surprised to need to replace it and that cold overnight just zapped out whatever little life was left.

Am I on the right path here? If it is the battery, I'm partial to Interstate but welcome any suggestions.

Thanks. Pat

 

Yes,,your on the right track.
Have the alternator checked before you buy a new battery.Might be time for a new Alt.
But this is the time of year that battery's crap out on ya.

Iv always had good luck with Interstate.

 

More than likely is the battery. There's an old trick for checking your own alt, with the truck running, pull off the positive battery cable. If the truck die's, it needs an alt, if it stays running, it's the battery. I've use this method many time over the years and it's allways worked for me.

 

original battery ?! would say it doesn't owe you anything!

anything made by johnson controls would be my choice

http://www.autobatteries.com/

 

Always pull the negative cable. This will keep spiking to a minimum as the battery acts as a filter. Some will tell you to positively not do this, but the danger comes when the regulator has puked and the voltage is way high. I have done this a couple of times with no consequences, but there is always that one time. Use your own judgement. However, I would not recommend this method on later model trucks, 03 and up.

The best way is to put a voltmeter across the battery terminals. 13.5 to 14.5 volts with engine running. jd

 

that would be the very first thing to do ! it tells you a lot.

there is the case that a bad battery will also take out the alternator before long.
don't wait until the battery explodes on you due to a shorted plate (been there= not pretty)

 

I'd run this puppy by your favorite autoparts store for a complete electrical system check up, via their portable system tester & with all the system accessories in place as is.

This tester when correctly used, can properly load test the battery, alternator & cables & can sniff out any problems.

I'm still on my OEM Motocraft battery in the Ranger & the 94 Taurus had it's OEM battery replaced with another Morotcraft in 00, so I've had good service out of Motorcraft/Johnson Controls products.

Let us know what they find.

 

If the battery light is fluttering Then I believe you will find a bad alternator a diode has gone bad. The safest test is with the volt meter. Another simple test is take a screw driver or some thin steel tool and touch the back of the alternator where the bearing housing is and see if it is has magnetic attraction while engine is running. If does alternator is putting out if not then something is wrong with the alternator or wiring to it.

 

Thanks everyone for the feedback. There is another data point to share that may be relevant and which I posted on some time ago. At high engine speed (>4000RPMs) the check battery light would flutter on, and would disappear when the throttle was reduced. As long as I stay below 4k RPMs, things are fine and I rarely rev that high so it was not a problem. I suspected the belt tensioner and was going to replace it but then winter arrived. A test at AZ around September showed the alternator was fine. I plan to retest it this weekend.

Pat

 

It's your alternator as I had exact same symptoms, ok under 4k. Voltage would go from 14.3 down to 12v using a voltmeter across battery terminals when rpm hit 4k. New alt fixed it.

 

I rebuild these g3 Ford alts and what I have seen a lot of is the slip rings wears really bad especially on the positive brush. And the symptoms are as you describe fluttering or a low glow on the battery light at higher rpms. The G3's are not bad about losing diodes. It may or may not test good. You can take the voltage regulator out and look at the slip rings and it you see a deep groove then its time to replace the rotor and brushes in the alternator. Most folks just buy a rebuilt and go on.

 

i'd say do a load test on the battery, and at the same time see what the alt is doing!
just a suggestion here, take a look at your belts or if its a serp belt take a look a the tensioner see if it flops around alot.

ford ranger

 

on my truck i've hit the rev limiter often and i donnot have that problem! real dependable,have drag raced the li'l truck no problems. 0-60mph in 4.5 seconds! and it's my daily driver

ford ranger

 

Here are my thoughts on your situation. The fluctuation in voltage on the dash light suggests to me that some problem exists with the alternator, the alternator regulator, the drive belt, or the +/- cable connections to the alternator. Generally, I don’t like jump starting a badly discharged battery and recharging with the alternator. The reason being that the charge produced from a good alternator is a high amperage charge. The batteries used in most automobiles have thin plates that do not tolerate high amperage charging well, but sometimes the only practical solution is to jump start. When I am faced with this, I would jump and idle the engine for at least 30 minutes or so. Another way to solve the problem requires knowing the amperage output of the alternator and then turning on accessory loads such as lights, A/C or heater, rear defogger, etc to reduce the amperage available for charging.
When I got the car home I would proceed to evaluate the battery. First thing in the morning, without starting the engine, turn on the headlamps for one second to eliminate surface charge, then disconnect the battery (with engine off) and measure the battery voltage with a digital voltmeter. If the battery is fully charged and in good condition, it will be 12.6 or 12.7 volts. If it is higher than 12.7, it still has a surface charge so I would turn the headlamps on for another second or two. If voltage is less than 12.6, e.g. 12.4, the battery is only partially charged or is showing signs of wear and I would charge it using a 6 amp slow charger. The more it is showing signs of age/wear, the quicker the voltage will rise through the bulk stage of charging to the acceptance charge of 14.4 volts. This might be over minutes or an hour. When the charger is removed, the voltage will very quickly will drop to a partially charged voltage—again this could be from minutes to an hour. If it drops to the same voltage that it started with, it either indicates that the battery needs more charging or that the battery can ‘t take a charge. A partially charged battery in good condition will increase voltage from 12.4 to 14.4 over a longer period of time-several hours to 24 hours with a low amperage charger. If you use a high amperage charger, the high amperage alone may cause a fast voltage rise even in a good battery. Batteries can fail in a sudden catastrophic way or gradually die from old age. This method is a good poor man’s way of determining how much capacity is left in the battery.
Second I would check battery cables and measure voltage drop in the various cables. I have had a car that had very similar problems as you describe and the problem was poor connections to the starter. I was getting ready to replace the starter and jacked the car up on one side to get to it. Just before removing it, I tried starting the engine one more time and it fired right up. I took the jack out and then tried to start it again and it wouldn’t start. Repeated this a few times and got the same result each time. Moving the car affected the connections. The car was a 1971 Lincoln Continental, which I still have, but I have forgotten whether it has a full frame or part unibody. At any rate, the problem was solved by cleaning the positive and negative battery cables at both ends, which made a good connection from the battery to the starter. Often when an alternator or starter is replaced with a rebuilt unit, simply removing and reinstalling the cables solves the problems of corrosion or bad connections. At times, putting in a new battery with higher voltage capability will appear to do the same thing.
Regarding disconnecting alternators while running---on at least one occasion, I incurred diode failure because of a disconnected alternator cable while the engine was running so I always use avalanche diodes to prevent alternator diode failure if there is a break in cable connections. Some of the higher quality battery disconnect switches (seen in motorhome/heavy-duty truck applications) have these avalanche diodes built in. When alternator diodes fail, there is usually only partial failure. This means that some of the diodes survive and the result may be diminished output rather than no output. This can lead to a chronically undercharged battery. Depending how the battery warning light is wired, it could lead to a partially “on” battery light. Various manufacturers wire the warning light differently and since I have not had a problem in any of my Rangers or B2300, I haven’t bothered to learn the exact method Ford uses.
Given the length of this post, it is hard to imagine that I could say more about batteries, charging, and alternators, but I can. However, I won’t say it now.
Regards..Ed

 

Thank you all for the great feedback. Here is an update.

I returned from my business trip Friday late afternoon and when I arrived to the airport park place, the valet attendant had retrieved the truck and it was idling warming up. I spoke to the attendant and he said it started fine (after sitting all week in mostly sub-freezing temps), and remembering my comments when I dropped it off he actually had anticipated a problem. I got in the truck and the voltage gauge was reading in the normal operating range with the engine at idle. But as soon as I got out of the parking lot, the voltage reading dropped to L and the check battery light was solidly lite. I headed on my 30 mile trek with all the electrics off and the wife on standby. Just before I arrived home, I turned on the headlights, heater blower, and it was obvious the battery was drained. I doubt I could have gone much further.

So today I am going to tackle this problem and as planned and suggested I want to take it to AZ to do a diagnostics on the charging system. But I have a few questions:

1. I am thinking the battery is not the problem.

2. Will the AZ diagnostics test determine if the voltage regulator is bad?

3. Assuming the alternator may be the culprit, I checked Motorcraft parts and they offer only remanufactured alternators. Is there anything wrong with purchasing an alternator from AZ?....I mean are all remanufactured alternators basically the same? If AZ provides a free diagnostics I would like to patronize the store.

Pat