1999 RX300

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#1
Please fill out the following to ask a question.

MAKE:Lexus
MODEL:RX300
YEAR:1999
MILES:283000
ENGINE:6
DESCRIBE ISSUE....
Lights flicker intermittently appears to be in charging system. Low voltage coming from alternator 12.7 to 13.2 volts during these cycles.
What I have done:
Replaced voltage regulator and rotor.
Problem went away for a week but has now returned as before intermittently.
Is there something in the system that could be sending the voltage regulator a false signal?
No codes being thrown. shifting is rough during the flickering cycles.
Is there an easy test to determine if its the alternator or other issue?

Thanks
 
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#2
maybe a alternator output test to include diodes, amps etc... Sometimes heat will affect so best is on vehicle as opposed to bench.
The wiring to alt may need checking - ign switch etc look at attachment
Hopefully there are no wiring 'modifications' remote starter AKA POS.

How do you know there are no codes? And will your scanner read all modules and codes?
 

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#3
No my scanner is a simple handheld so there may be codes that I cant read. The service engine light is not on, that about as far as I can read on that aspect.
There are no add like remote starting.
I did have a problem back a few months ago when the fuel injector relay would keep clicking unless the key was in contact with the ignition. we clipped the wire an the base of the ignition switch that kept the relay from clicking until the battery would die. I lost my key chime but it fixed the problem. not sure if this could be related to that.
My voltage measurements were on the car at operating temperature. The operating temperature is a common denominator as the flickering does not occur until the engine is at normal operating temp.
I'm thinking of replacing the alternator all together and wanted to see if there were other possibilities before the alternator swap.

Thanks
 
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#4
The CEL will not turn on for all codes. And sometimes code readers are 'lacking' - esp the low priced ones.

I would look closer at the issue with the ign switch, clipping wires is a red flag so might want to double check that.
Do you need more wiring diagrams?

The gang will stop by and add their ideas later. Some are very familiar with Toyota electrics.
 
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#5
Have you noticed a whining sound from Alt when the problem occurs? If so, I would suspect a problem in the stator/diode portion of the Alt.

While the problem is occurring, use a jumper wire to create an additional "+" circuit between Alt and battery. If that makes no difference, use jumper wire to create an additional "-" circuit between Alt and battery, and if that makes no difference, use jumper wire to create an additional "-" circuit between Alt and engine, and if that makes no difference, use jumper wire to create an additional "-" circuit between Alt and body/chassis.
 
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#6
Thanks Dan,
I'll perform the check this afternoon and reply with the results.
My previous readings were the Alt to the battery "-" There was quite a bit of fluctuating during those readings particularly when the AC Compressor kicked in. But the strongest readings was in the low 13 volt range.
 

billr

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#7
Measure AC voltage right at the alternator output stud/terminal. If more than about 1VAC, the rectifier diodes are suspicious.