Alternator problems

[Chris67]

Any tell tale signs that your alternator is going bad? Could it affect the defrost system (pulling power or making it work harder?) I noticed driving down the street that the lights go brighter when the ac clutch disengages. Please help. I have a good battery and replaced the belt

 

[WaCumminstech]

If the alternator is going bad an easy way to tell, is to turn all electrical loads on, at idle, and watch what happens. If the alternator is failing coming up to around 1800 rpm wont help. Also look for bad ground connections. If cruising down the highway you arent able to charge/power your systems, then id look to the alternator.

 

[Chris67]

I have all power going down the road. At idle I at @900 rpms...what should I be at? defrost seems to make the most strain when it kicks in. headlights seem to dim

 

[OneLever]

Buy a cheap multimeter. Test the voltage (VDC) across the battery terminals with the engine off. Should read around 12.3 V. Turn the engine on. Check voltage across the terminals. Should read around 14.4 V. Post your results.

This is good place to begin: Alternator search

 

[edwx]

The alternator on my '03 XLS failed instantly. Was working 100%, then not at all. Believe me, you'll know it when it fails. Like OneLever said, 12.3 and 14+. I bought one of those meters you pulg into the 12v port to monitor battery and alternator. They are really cool...at Walmart in the car battery department for about $15. Maybe it's your battery and not the alternator.

 

[Chris67]

Tech at autozone checked the battery when explorer was off and said it was fine. I don't know how old the battery is since I bought the car used but in the battery indicator window its green

 

[imp]

The alternator on my '03 XLS failed instantly. Was working 100%, then not at all. Believe me, you'll know it when it fails. /QUOTE]

Alternators USUALLY fail more gradually, and in my experience with them, most often their output falls, due to worn brushes which beging to make "iffy" contact with the "slip rings", thereby reducing the unit's output capability.

The dimming of lights when more and more electrical load is added (blower, a/c/, etc.) strongly points to that type of condition. But, semantics, the alternator will need to be rebuilt/replaced either way. If voltmeter check shows battery voltage over say, 13 volts when running, with all electrical accessories off, at least the vehicle may be driven awhile without draining down the battery. If the alternator's output is zilch, or nearly so, the vehicle will be running on the battery alone, draining it to the point where it will not re-start the engine. imp

 

[WaCumminstech]

OK Guys, VOLTS and AMPS are different things, Yes the Alternator should be producing Approx 14.5v at ALL times, BUT at idle ALternators are rated at a specific amparage, and at "cruise" they are rated at another Higher amperage. so an explorer alternator at idle should be rated around 50 amps, while at cruise it may be rated at 90. Now back to my directions turn on all loads, at idle, and see what happens, after 5-6 minutes at idle lights are starting to go out, then your alternator has one of two issue, either your load has gone up, or your amperage output has gone DOWN, your load going up points back to a BAD connection, amperage going down points to failing alternator. Go back to auto zone and ask them to test the charging system instead of the battery

 

[WaCumminstech]

ANother disclaimer about Battery Windows, that little floating ball in side can stick.
DONT EVER PUT TAP WATER IN A BATTERY, Use DIStilled, poring regular water in can cause an internal short, which kills a battery.
Optima batteries IMHO are the best money can buy, I have had 3-4 that have worked wonders in the worst of conditions.

 

[imp]

......./Optima batteries IMHO are the best money can buy, I have had 3-4 that have worked wonders in the worst of conditions.

Are those the batteries advertised in performance publications, some of them are sealed, or can be tipped over? imp

 

[WaCumminstech]

Are those the batteries advertised in performance publications, some of them are sealed, or can be tipped over? imp

Yea, instead of using water, they use a lead acid gel that doesnt leak, aka "Red top" last one i tossed would still start and run my jeep with a dead cell.
normally around 200 for a new one, but they have a 3 year warranty and in my experience normally last close to seven well worth the value

 

[not8taxi]

sorry to hijack thread...i have a yellow top optima...is it possible the battery shows its good and have the dead cell like you said?

 

[Chris67]

Yes it is....I suspected mine was stuck as well...replaced battery and all systems go as tthey say

 

[WaCumminstech]

sorry to hijack thread...i have a yellow top optima...is it possible the battery shows its good and have the dead cell like you said?

As far as i know, No. My Professional tester told the battery had a bad cell. ANd my jeep was slow cranking, But it would still start, and all systems were working. Red tops are SLI (starting lights ignition) style, they have a high starting amperage but low stamina. Yellow tops are a mid way between SLI and deep cycle. A Blue type is DEEP cycle, designed to have a slower discharge rate over a longer period of time(listening to the radio all night then start your car in the morning). Now of course running a battery past 50% everyday cuts its life time down quickly.

 

[silverstang07]

Tech at autozone checked the battery when explorer was off and said it was fine. I don't know how old the battery is since I bought the car used but in the battery indicator window its green

i'd say bring it in to autozone if they have the same thing we do at work their tester should be able to check both the battery and the alternator as for the indicator window I do not advise going based on that because if shaken just a little bit that ball changes to red

 

[matt0248]

Just a little FYI, Alternators usually charge aroung 13.5 Volts or so when the engine is hot, They charge higher when the engine is cold, about 14.3 Volts. A battery should be at 12.6 Volts when there no load, (vehicle not running), if it as 12.3 Volts it is under charged and should be charged before testing.

The test described above is a very good test to see if your alternator can "keep up" with the loads at idle. IF you run on all accessories, AC, high beam headlights, rear defrost and let the engine idle the alternator should be able to keep up. Meanign it should keep the system voltage above 12.6 at a bare minimum. You should see the voltage slowly drop and stabilize at a certain voltage (different for different cars). IT should maintain that voltage indefinately. If the voltage continues to drop or drops below 12.6-12.8 that this is an indication that alternator is weak.

 

[psu x]

Possible solution not suggested yet

I know this is a really old thread, but I had a similar issue and have a completely different solution. I had the same dimming lights, varying blower speed, etc. After replacing the alternator,the issues did not go away. The problem I found was actually that my throttle body was dirty. So my RPMs were low - around 900rpm like yours. It happened at idle and when coasting, especially with lights and brake lights on. I thought the engine might even stall at times.

So after getting the throttle body nice and clean, the throttle response was greatly improved which was a bonus and the RPMs are steady at 1100 at idle/coast and the electrical system is much happier.

I think the throttle-by-wire can't properly control the engine RPMs when the throttle body is gummed up. So it can't adjust the throttle to keep the rpms steady during the varying loads on the alternator. My old explorer had an idle air control that worked off of vacuum, so this never happened.

I also think (but don't know for sure) that the low RPMs might have resulted in premature failure of my 2nd... And 3rd...alternators. It seems to make sense to me that if it is trying to crank out more watts from less rpms that it could cause undue strain on the voltage regulator or other components. That's just a thought.