I have a feeling that my alternator is bad in my 2013 RAV4 with only 60k miles on the clock. But it's just a feeling. No battery lights, no drained batteries, no squealing, no noises, just a hunch and slightly low voltage (dips into the high 12s on a few occasions at idle). O'Reilly's in car tester said bad voltage regulator. I know I could take it out and get it bench tested as well. But is there a better way to test an alternator than use the bench tester in the back of the store? Or is the bench tester pretty much the gold standard?
Most reliable way to test alternator?
- Thread starter Deontologist
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At 60K I doubt it is bad... As long as it is the original and not a crapshoot reman.
It should be putting out about 14.2 volts at idle, I believe.
Good luck.
It should be putting out about 14.2 volts at idle, I believe.
Good luck.
My experience with the bench tester is that they can easily be wrong. Most cars today have their voltage output regulated by the on board computer and can fluctuate quite a bit based on demand and how the computer is programed. High 12s to 15 and anywhere in between with fluctuations up and down as you drive is totally normal on modern cars. Manufactures do this to increase MPG when a higher charge rate is not needed and prolong battery life by monitoring current draw and state of charge. Gone are the days when you expected a constant 13.5 to 14 v charging rate.
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Originally Posted by mk378
Yes this sounds typical for a "smart" charging system. Possibly if you turn the headlights on the voltage will come up and stay more steady.
It actually dips quite a bit with the rear defroster being switched on. I'll have to observe it again today, but the other day, I had a voltage monitoring device plugged into the cigarette lighter and I noticed that by turning on accessories, I could get it to dip a rather concerning amount. I guess I should also see what the FSM says about the alternator's output range.
The other reason I've been suspecting the alternator is that the headlamps are unbelievably dim. The lamps have brand new, upgraded bulbs and I've personally aimed them with an aiming machine. I remember then being better when I first purchased the vehicle. My 2006 Camry outshines the '13 RAV4 by a country mile.
I almost want to drop an alternator into the RAV4 and see what happens, but I'd rather not be one of those "trial and error" mechanics!
Finally, the O'Reilly catalog had 2 different alternators, one for FWD RAV4s and one for AWD RAV4s. The FWD RAV4 alternator specifically said "DO NOT BENCH TEST, TEST IN-VEHICLE ONLY!!!" Why is that?
Yes this sounds typical for a "smart" charging system. Possibly if you turn the headlights on the voltage will come up and stay more steady.
It actually dips quite a bit with the rear defroster being switched on. I'll have to observe it again today, but the other day, I had a voltage monitoring device plugged into the cigarette lighter and I noticed that by turning on accessories, I could get it to dip a rather concerning amount. I guess I should also see what the FSM says about the alternator's output range.
The other reason I've been suspecting the alternator is that the headlamps are unbelievably dim. The lamps have brand new, upgraded bulbs and I've personally aimed them with an aiming machine. I remember then being better when I first purchased the vehicle. My 2006 Camry outshines the '13 RAV4 by a country mile.
I almost want to drop an alternator into the RAV4 and see what happens, but I'd rather not be one of those "trial and error" mechanics!
Finally, the O'Reilly catalog had 2 different alternators, one for FWD RAV4s and one for AWD RAV4s. The FWD RAV4 alternator specifically said "DO NOT BENCH TEST, TEST IN-VEHICLE ONLY!!!" Why is that?
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Originally Posted by DerbyDave
My experience with the bench tester is that they can easily be wrong. Most cars today have their voltage output regulated by the on board computer and can fluctuate quite a bit based on demand and how the computer is programed. High 12s to 15 and anywhere in between with fluctuations up and down as you drive is totally normal on modern cars. Manufactures do this to increase MPG when a higher charge rate is not needed and prolong battery life by monitoring current draw and state of charge. Gone are the days when you expected a constant 13.5 to 14 v charging rate.
Great post here ^^^^^
My car going down the road is typically running 12.88 to 13.20 volts...
My experience with the bench tester is that they can easily be wrong. Most cars today have their voltage output regulated by the on board computer and can fluctuate quite a bit based on demand and how the computer is programed. High 12s to 15 and anywhere in between with fluctuations up and down as you drive is totally normal on modern cars. Manufactures do this to increase MPG when a higher charge rate is not needed and prolong battery life by monitoring current draw and state of charge. Gone are the days when you expected a constant 13.5 to 14 v charging rate.
Great post here ^^^^^
My car going down the road is typically running 12.88 to 13.20 volts...
I usually look at the Duty Cycle vs Desired Voltage chart.....It the DC on the scan tool matches the output voltage (Approximately). I call it good.
DIL's '09 -ish Rav 4 set a code for something that will flunk inspection.. It is a sensor that needs to see a certain voltage is lookin more a marginally higher V than necessary. Fix is a fully charged battery. I gave him a HF,floater and it worked to quiet code. and get sticker..
I put a clamp-on DC ammeter onto my alternator's main charging line one time. It gave some interesting numbers as to when it was feeding current into the system and when it wasn't. With everything maxxed out, the alternator could not hold the system at idle RPM, but more speed definitely helped.
Originally Posted by Deontologist
just a hunch and slightly low voltage (dips into the high 12s on a few occasions at idle).
Depending on load, the idle AND voltage can drop. When I kick on the secondary AC in my suburban, the idle drops well below normal. It's normal for the idle to drop and recover when the cabin AC is turned on, but I also have a secondary AC in the back of the truck and when it's engaged, the idle noticeably takes another dip and doesn't really fully come back to "normal".
If you're experiencing a similar thing, where your idle isn't really keeping up with demand, then maybe the alternator is lacking a bit. Before you change it out, is the belt properly tensioned and in good condition? Is your idle stepper solenoid working properly?
just a hunch and slightly low voltage (dips into the high 12s on a few occasions at idle).
Depending on load, the idle AND voltage can drop. When I kick on the secondary AC in my suburban, the idle drops well below normal. It's normal for the idle to drop and recover when the cabin AC is turned on, but I also have a secondary AC in the back of the truck and when it's engaged, the idle noticeably takes another dip and doesn't really fully come back to "normal".
If you're experiencing a similar thing, where your idle isn't really keeping up with demand, then maybe the alternator is lacking a bit. Before you change it out, is the belt properly tensioned and in good condition? Is your idle stepper solenoid working properly?
Originally Posted by andyd
DIL's '09 -ish Rav 4 set a code for something that will flunk inspection.. It is a sensor that needs to see a certain voltage is lookin more a marginally higher V than necessary. Fix is a fully charged battery. I gave him a HF,floater and it worked to quiet code. and get sticker..
There are diodes that can replace the 5 amp "alternator sensing" fuse. The Alt-S fuse is part of the cars alternator monitoring system.
In my beater 06 Camry with a lifetime warranty reman alternator, I replaced my Alt-S fuse with an adjustable diode, which can create an large as a 1 volt drop across the sensing circuit. In effect, the computer is fooled into thinking that the voltage coming out the alternator is always 1 volt too low, and this pegs the alternator at a constant 14.2 volts in the car. The low beams on the Camry rival HID systems, and even lifted pickup trucks can't stand my high beams, with 14.2 volts flowing to them. Lumen output increases exponentially by a factor of 3.4 with voltage.
Just a little aside, in case you ever take the HF float charger back or if they get tired of hooking it up.
DIL's '09 -ish Rav 4 set a code for something that will flunk inspection.. It is a sensor that needs to see a certain voltage is lookin more a marginally higher V than necessary. Fix is a fully charged battery. I gave him a HF,floater and it worked to quiet code. and get sticker..
There are diodes that can replace the 5 amp "alternator sensing" fuse. The Alt-S fuse is part of the cars alternator monitoring system.
In my beater 06 Camry with a lifetime warranty reman alternator, I replaced my Alt-S fuse with an adjustable diode, which can create an large as a 1 volt drop across the sensing circuit. In effect, the computer is fooled into thinking that the voltage coming out the alternator is always 1 volt too low, and this pegs the alternator at a constant 14.2 volts in the car. The low beams on the Camry rival HID systems, and even lifted pickup trucks can't stand my high beams, with 14.2 volts flowing to them. Lumen output increases exponentially by a factor of 3.4 with voltage.
Just a little aside, in case you ever take the HF float charger back or if they get tired of hooking it up.
Hmmm, I was thinking just the opposite(it's just how my layman brain works).
I am thinking that everything is normal and the battery is in fact fully charged, allowing for the alternator to take a break, kickback & relax for a bit.
Anyone else?
I am thinking that everything is normal and the battery is in fact fully charged, allowing for the alternator to take a break, kickback & relax for a bit.
Anyone else?
Check battery resting voltage with multimeter. If good then start engine and check voltage to battery with multimeter.
Resting Voltage 12.6V approx.
Engine Running 14V approx. at battery.
Load Test- turn on everything and test voltage at battery. If voltage lower than 13 or higher than 15... suspect alternator.
Resting Voltage 12.6V approx.
Engine Running 14V approx. at battery.
Load Test- turn on everything and test voltage at battery. If voltage lower than 13 or higher than 15... suspect alternator.
Originally Posted by Deontologist
Lumen output increases exponentially by a factor of 3.4 with voltage.
Yeah, but lifespan goes as v ^ -16. Are you replacing your headlights monthly??
Lumen output increases exponentially by a factor of 3.4 with voltage.
Yeah, but lifespan goes as v ^ -16. Are you replacing your headlights monthly??
I am guessing here , but is the voltage regulator built into the alternator or is that function taken care of by the " computer " .
I agree , use a meter to check the battery voltage , alternator voltage and amperage .
I agree , use a meter to check the battery voltage , alternator voltage and amperage .
Originally Posted by benjayman227
Originally Posted by Deontologist
Lumen output increases exponentially by a factor of 3.4 with voltage.
Yeah, but lifespan goes as v ^ -16. Are you replacing your headlights monthly??
They are covered by a 1 year warranty at O'Reilly. They don't ask too many questions. The Vosla/Sylvania XtraVision 9012+30 bulbs barely make it to a year with normal voltage anyway. Safety is more important to me than bulb life, and I get free replacements anyway.
Originally Posted by Deontologist
Lumen output increases exponentially by a factor of 3.4 with voltage.
Yeah, but lifespan goes as v ^ -16. Are you replacing your headlights monthly??
They are covered by a 1 year warranty at O'Reilly. They don't ask too many questions. The Vosla/Sylvania XtraVision 9012+30 bulbs barely make it to a year with normal voltage anyway. Safety is more important to me than bulb life, and I get free replacements anyway.
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It's normal for voltage to fluctuate. Newer alternators are controlled by the ECU and have load sensors to monitor electrical load. The idea is to minimize load on the alternator, and to be smarter about the battery charging so it lives a long life. The voltmeter on my Traverse could fluctuate significantly, because the alternator would switch between high output and low output; it did not change the output linearly. I recall from the service manual it also took the headlights into consideration and it would lower the maximum voltage it could put out so the bulbs lasted longer if the lights were on. To a casual observer it might appear the voltage is drooping because the lights are loading it down, but that's not the case.
The official procedure I recall from my 2008 Honda was to load it down with a carbon pile with the engine running, and if it was maintaining at least 13.6 volts at 1000 RPM it was good. The battery box at Autozone deemed my alternator as faulty when I had the battery tested, but I suspect the box was intended to test conventional alternators that only try to maintain a constant voltage. I didn't have a carbon pile, so I turned on everything possible (headlights, rear defroster, A/C, fan on high, interior lights, fog lights, radio, brake lights, wipers, etc.) and made sure it met the spec.
The official procedure I recall from my 2008 Honda was to load it down with a carbon pile with the engine running, and if it was maintaining at least 13.6 volts at 1000 RPM it was good. The battery box at Autozone deemed my alternator as faulty when I had the battery tested, but I suspect the box was intended to test conventional alternators that only try to maintain a constant voltage. I didn't have a carbon pile, so I turned on everything possible (headlights, rear defroster, A/C, fan on high, interior lights, fog lights, radio, brake lights, wipers, etc.) and made sure it met the spec.
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