99 es300 will not charge battery if rpms are under 1200 and has new battery and have tried 3 different brands of alternators.All wiring is good and am getting power to all wires at alternator.Still have the same problem.

I bought this car with this problem,it has not had anything added to the system.The grounds are the only thing i have not check yet but i have not seen anything off hand loose.As far as pulley size it has the one that came on the car so that should not be the problem.In most cases if the igniter wire is hot to the alternator it should charge at idle as well as higher speeds.You can turn off all accessories and it does the same thing.There are three wires on the plug can anybody tell me what kind of power or grounds are supposed to be there when running are not.I have a wiring diaghram but it does not lell what is on each wire at all times running are not.

I bought this car with this problem,it has not had anything added to the system.The grounds are the only thing i have not check yet but i have not seen anything off hand loose.As far as pulley size it has the one that came on the car so that should not be the problem.In most cases if the igniter wire is hot to the alternator it should charge at idle as well as higher speeds.You can turn off all accessories and it does the same thing.There are three wires on the plug can anybody tell me what kind of power or grounds are supposed to be there when running are not.I have a wiring diaghram but it does not lell what is on each wire at all times running are not.

Every connection is clean and tight.With a volt meter on the battery the volts go from 14.2 at 1300 rpms and up and at 1200 rpms and down the volts start dropping until the battery will not run the car anymore.

Every connection is clean and tight.With a volt meter on the battery the volts go from 14.2 at 1300 rpms and up and at 1200 rpms and down the volts start dropping until the battery will not run the car anymore.

OK - the alternator works and the battery charges above 1200rpm. I believe the stock alternator for the 99 ES 300 puts out about 80 amps max, so at idle there's going to be a pretty significant voltage drop - BUT it sounds like an RPM problem; above engine RPM of 1200, everything's OK.

I'd check for belt slippage, wrong length belt or malfunction of belt tensioner. Good Luck! OK - the alternator works and the battery charges above 1200rpm. I believe the stock alternator for the 99 ES 300 puts out about 80 amps max, so at idle there's going to be a pretty significant voltage drop - BUT it sounds like an RPM problem; above engine RPM of 1200, everything's OK.
I'd check for belt slippage, wrong length belt or malfunction of belt tensioner. Good Luck!

Thundergod is correct; a smaller alternator pulley would produce higher RPM's and higher voltage output at idle, but I would not think you have to go that route for a stock alternator with stock elec. equipment.

This may seem like a simplistic question, but how do know the alternator is not charging at idle? What are the symptoms? Does your instrument cluster have a voltage gauge. If so, what does it read at idle?

I take it that the BATTERY TERMINALS are really clean - no corrosion, and the ground wire to engine connection has been checked for corrosion.



Again, check for belt slippage and/or belt tensioner function. Thundergod is correct; a smaller alternator pulley would produce higher RPM's and higher voltage output at idle, but I would not think you have to go that route for a stock alternator with stock elec. equipment.
This may seem like a simplistic question, but how do know the alternator is not charging at idle? What are the symptoms? Does your instrument cluster have a voltage gauge. If so, what does it read at idle?
I take it that the BATTERY TERMINALS are really clean - no corrosion, and the ground wire to engine connection has been checked for corrosion.

Again, check for belt slippage and/or belt tensioner function.

Have you added any high power audio equipment or driving lights prior to the no-charge problem?

Are you having the no- charge problem regardless of whether lights, accessories, blower, etc.., are on or off?

Have you checked the GROUND(s) connection(s)?

Have you replaced the drive belt or checked to see if the belt is slipping?

Have you added any high power audio equipment or driving lights prior to the no-charge problem?
Are you having the no- charge problem regardless of whether lights, accessories, blower, etc.., are on or off?
Have you checked the GROUND(s) connection(s)?
Have you replaced the drive belt or checked to see if the belt is slipping?

See if you can find a smaller front alternator pulley it will turn the alt faster. problem may not be electrical.
See if you can find a smaller front alternator pulley it will turn the alt faster. problem may not be electrical.