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Discussion Starter #1
So I have a 2004 I4 Rav4 and recently my wife was driving it and lights started coming on on the dash and then the car stalled. Went and jump started her got the car home checked voltage on the battery and it was below 10. Havent changed the battery in quite a few years so I changed the battery. The next day the exact same thing happened. Charged the battery, pulled the negative terminal off the battery (I know this isnt good for it) and the car died. So I went and got a new alternator put it in and baam same thing happening but this time I get a check engine light for the VSS (vehicle speed sensor A) being bad so I change that, charge the battery and same thing, no luck. When I start the car it only shows it in neutral regardless of what gear I am in and the fan blower does not work. Everything else on the car works (radio, lights, horn, wipers, turn signals, etc).

I checked all the fuses to included the fusible fuses attached to the battery connection and they were all good. I asked around to a few of my local mechanics and they say its the alternator, but how many of you have seen a alternator bad out of the box? Also when I check the volts to the alternator from the battery its the same as if I was checking the terminals on the battery.

So please any and all help would be greatly appreciated. Thanks everyone!!!
 

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Since you already have a voltmeter, checking for proper alternator output is simple.

The battery voltage will read "about" 12volts when the engine isn't running, and this voltage should rise to 13.8-14.8 volts when the engine is running. The exact voltage will vary depending on temperature and battery condition, but the key point is the voltage should rise at least 1.5 volts when the engine is running. ( please no debates on exact voltage, this is a go/no-go test i.e. the KISS rule)

Since your car is starting, I expect the battery is in good condition, and therefore the warning lights are probably not even related to the alternator.

I expect when you jump started the car, that a fuse has probably been blown. But let's start by proving the alternator is working.
 

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Discussion Starter #3
I DO NOT get a spike in voltage when I start the vehicle, the volts only drop. I tested the ohms on the continuity between the positive terminal and the alternators output stud with the batteries negative terminal disconnected and it read the correct .5 ohms also. I checked the fusible fuses and they check good on both sides of the connections.
 

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Your Humble Administrator
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It's not unheard of for a re-manufactured alternator to be bad out of the box. Remove it, bring it back to where you bought it and have them test it.
 

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Well we know the alternator is not outputting any power, but before saying the alternator is bad, there are 4 fuses involved in the circuit.


  1. The 140 amp fuse, which you proved was OK when you measured the resistance from the + terminal to the alternator stud.
  2. The Alt-S 5 amp fuse located in the box under the hood, on the left side.
  3. The GAUGE 10 amp fuse located inside the RAV (drivers side J/B behind dash)
  4. The IG2 10 amp fuse also located inside the RAV
Does the "charge warning light" come on when the engine is running? If it doesn't, check the bulb by turning on the ignition but not starting the engine.
 

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Discussion Starter #7
ok thank you!!!! Checked the fuses and low and behold the 10 AMP GAUGE fuse was blown. Throw a new fuse in there car runs amazing, its charging the battery, volts jump up to 13.8 and then it starts running like crap and all symptoms return and the fuse is blown. What could cause that fuse to keep blowing?
 

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Discussion Starter #8
So now I replaced the fuse car starts everything works but runs like crap. I check the volts its looking good but stumbling all over the place. I disconnect the main plug from the alternator car smoothes out runs great. Reconnect the plugs car stumbles all over. Any insight?
 

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I'm not sure if the the Gauge fuse is now holding, or is it still blowing.

The GAUGE fuse is responsible for


  • The backup light switch
  • The A/T indicator light
  • Vehicle speed sensor
  • Passenger side J/B ECU
  • Fan 1 relay
  • Fan 2 relay
  • Fan 3 relay
  • The alternator
If the fuse is no longer blowing, and the alternator is outputting the correct voltage, I can't explain why your RAV runs poorly with the correct voltage of 13.8 volts and runs poorly when the voltage is only 12 volts (alternator disconnected).


Which cable are you disconnecting from the alternator? The one attached to the stud, or the multi-wire plug.
 

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the multiwire plug!
OK, I still don't know if the GAUGE fuse is still holding or blowing.

Since it is unlikely that the normal 13.8 volts is causing the engine to run rough, my theory is that the alternator is sending electrical noise into the wiring, and this noise is causing problems with the various on board computers.

You could try leaving the multiwire plug connected, and disconnecting the wire from the stud. This will also reduce the voltage, but if it still runs rough it may prove my theory about noise coming from the mutiwire connector.

Does the engine run well enough to go for a drive?. If so, reset the check engine light and take a drive to see if it comes back on. The error code should help pinpoint the cause of the problem.

Perhaps you could try disconnecting your new VSS since it is powered by the gauge fuse, and is something that you changed recently.
 

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Discussion Starter #12
ok well I changed the fuse took the car for a long ride and now everything is working fine and car is running great. Ill keep everyone posted. thanks everyone for all the help!
 

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ok well I changed the fuse took the car for a long ride and now everything is working fine and car is running great. Ill keep everyone posted. thanks everyone for all the help!
Good to hear.

If the alternator has not been working since you installed it, the battery was probably run down from the repeated testing.

Perhaps your initial "stumbling" was due to the high load the alternator was placing on the engine. As the battery became charged, and the alternator wasn't working as hard, the engine load decreased.
 

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After disconnecting the battery, the engine will often run rough until the engine computer learns all the parameters again.
 

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Hi...
Can i post my problem here??

Just got my first Rav4 2004 with diesel.
Today when i turn on the ignition.. batterylamp did not light up..
After starting the engine..the headlights and inst.light wont work.. before i rpm to 2500o/min.
Then the light turns on.. but now the batterylamp and fuelfilter lamp turns on..and the alternator is not charging.
Try to change alternator(bosch) checed the fuses.
Not the 140 amp.
But the rest is ok.
Any ideas on this problem ?
 
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