Mechanics

ES300 CHARGING SYSTEM PROBLEM

1998 Lexus ES 300 • 6 cylinder 2WD Automatic • 237,000 miles

1998 Lexus ES300 Charging System Problem
What should the alternator voltage output be at 800RPM with all accessories turned on?
History of car: It previously had a problem of a no start, lights dim, starter clicking symptom seldomly.
Battery was replaced two years ago and I had the battery load tested recently, currently shows 12.8V. The car had a problem with wanting to die. I charged the battery and drove the car to autozone where it was tested on car as bad voltage regulator. I replaced the alternator with one from Oreillys a rebuild Ultima Brand alternator. I drove the car for 3 weeks and the battery light came on, pulled car in parking lot and car would not start back up. Drove the car to oreillys and had them test it on the car and then bench tested. Bench test passed and test on car failed. All connections and cables have been checked. I went ahead and replaced it with a second alternator(same ultima brand) and drove it home. I checked with a voltmeter and noticed that with all accessories turned on except for the air conditioning the voltage output of the alternator shows 13.5V at 800RPM. When I turn the climate control on the voltage slowly drops down to 12.6 V at idle. When I turn the A/C off and leave the accessories on the voltage picks back up to around 13.5V.
I have checked the A/C clutch coil with meter reads 5 ohms.
I have temporarily jumped the clutch coil with 12V and car running without climate control inside turned on and voltage does not drop down with accessories turned on.
I noticed when running the A/C the compressor does not cycle on/off. I hooked up R134A gauge set on a cool engine and pressures read 110PSI low and 110PSI high without car running and outside temperature 93 degrees. Do you think an overcharged A/C system would cause the problem? Or a faulty A/C pressure switch?
Or do you think the alternator will not handle the load the car has because its cheap?
Any advice would help.
Thanks.

Avatar
Brandon24
July 27, 2011.




The charging system is not good if charging voltage drops drastically when elecrical loads are applied. It could be the alternator or the crank pulley ( damaged harmonic damper, if equipped).

I don't believe the overcharging of the freon is causing any problem to the charging circuit.

KHLow2008
Jul 27, 2011.


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