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Strange alternator problem

Ranajah

NAXJA Forum User
When I start my jeep in the morning the voltmeter will read 10 volts. The lights will be dim and the turn signals will blink slowly. When I raise the RPM to 1,100 the volts will go up to normal and the lights will work fine but will not stay there if I lower the RPM. When I drive it around for about 15 minutes and get the jeep up to operating temp the volts will read normal and lights work fine at idle RPM. The strange thing is that this never occurs in the summertime when it is warm out. Only in the colder months when it gets down to 40 degrees do I have this problem. I had battery and alternator tested at Autozone and everything was fine. However, next morning the same problem occured. Now that it is warm out I have no problem whatsoever with the charging system. What gives?

1989 XJ
4.0
31X10.5X15 Big Foot XT's
Dana 30 front TruTrac
Dana 44 rear PowerTrax Noslip
 
Autozone? That's nice - I don't bother with their tests...

Since you mention it happening when cold, I'm inclined to think "battery." When I was growing up in Lafayette, IN, we'd always know who had good batteries when the first frost hit - the ones who didn't were at the parts house buying new ones.

If you have room in your freezer, try this: put the battery on charge for several hours, prefereably until the battery retains a reading of 12.6V with the charger disconnected.

Put the battery in the freezer for, say, 10-15 minutes. The colder the better.

Take the battery out of the freezer, take it right to your rig, and use it to start the engine and let it run. If that problem comes up the same way, you're due for a new battery.

Since you have a 1989, you also have a Delco CS alternator, and I've noticed they're pretty solid. Besides, it sounds an awful lot like your battery to me - especially since you mention it happening when it gets cold overnight, and it goes away when the engine bay reaches operating temperature (~15 minutes is also about right for that.)

Those wifty little electronic load testers (Bear ARBST, no?) won't pick up on that - unless you take the battery in packed in ice. I don't bother with the thing - that's what's nice about having a large freezer.

If you don't have room in you freezer, get a large cooler and a bag of ice, and pack the battery in ice. You'll also be able to start the engine with a battery at ambient tempeature, and one that's been chilled - you'll see a difference.

I'd be willing to bet that if you took your battery in while it was cold, it would fail their test. Unfortunately, they just don't think that way.

5-90
 
What good is a Optima unless you need something you can lay on it's side.
They don't even have the CCA of a good standard battery if you compare spec's.
All the hype is because they can be shipped and sold online and standard batteries can't.
None the less just for a test, because you may need to change the Alt if you want to run the Optima.
 
Ranajah said:
I replaced my old Optima with a new one. Same Problem.

Did you do the "freezer test" like I'd mentioned? Even Optimas can have trouble with cold. Batteries depend on chemical reactions to work - if the electrolyte gets weak for some reason, cold can slow the reaction down to the point where you just don't get enough power.

It might be worth testing, even with the new battery, just to eliminate it as a cause. I don't see any reason why a system wouldn't work with an Optima, but I've not run into that yet. Langer, would you care to elaborate?

5-90
 
I would also take a really good look at your battery cables and your grounds. I know my cables are not in the best shape, and if I let them go long enough, I will have problems. I take them off and clean the hell out of then ends every so often.
 
langer1 said:
Optima has such a high Resistance that some regulators think their fully charged when they are not.

Interesting. How'd you find this out, just out of curiousity? I'd not heard it before, and I'm not having trouble with either of the Optimas I've got (in an 88 and an 89.) I'm actually quite fond of them - they've proven rock solid in service, and I don't see any real reason to change back (touch wood...)

5-90
 
5-90 said:
Interesting. How'd you find this out, just out of curiousity? I'd not heard it before, and I'm not having trouble with either of the Optimas I've got (in an 88 and an 89.) I'm actually quite fond of them - they've proven rock solid in service, and I don't see any real reason to change back (touch wood...)

5-90
By selling them for about 4 years and having to deal with a 25% failure rate as opposed to 5% for our standard line.
If they last a year you don't have anything to worry about though.
 
Interesting. So, you'd never tried getting hold of Optima - get the story straight from the horse's mouth? Just wondering - this is most curious, and I do try to make sure I'm edified on things like this...

I find it interesting that my local doesn't trust their Bear ARBST tester on Optima batteries, either. It passes failures... Go figure - maybe a facet of the same problem?

5-90
 
5-90 said:
Interesting. So, you'd never tried getting hold of Optima - get the story straight from the horse's mouth? Just wondering - this is most curious, and I do try to make sure I'm edified on things like this...

I find it interesting that my local doesn't trust their Bear ARBST tester on Optima batteries, either. It passes failures... Go figure - maybe a facet of the same problem?

5-90
Sure but they never fully explained it only that it was difficult to hold Manufacturing tolerances.
We use PowerSonic AGM battries in our Fire Trucks and love them.
 
I've used Optima batteries for about 6 years and I've never had this problem before. I've checked all the cables and they're all good. I'll try the battery in the feezer trick this weekend just to be sure.
 
langer1 said:
Sure but they never fully explained it only that it was difficult to hold Manufacturing tolerances.
We use PowerSonic AGM battries in our Fire Trucks and love them.

Interesting. Do they have a website? I've been looking at a lot of aircraft batteries for auxiliaries lately, and I'd like to have more options (and I'm figuring you'd probably know, saving me the search.)

I'd be interested in hearing more of what you might know about batteries, just for my own edification. Where did you work when you were selling them, anyhow? Parts house, Electrics house, or a battery house?

5-90
 
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