Suzuki Vitara Alternator??

[slayer921]

I have a suzuki vitara that has recently developed a fault where if i turn the lights or the heater on, it revs up to about 3000 rpm!! Is this an alternator fault?? At night its like a cruise control at 35mph in 5th!! Battery has been checked and seems fine!! Wot could it be???

Thanks for you responses in advance!! Tom

[logic]

try slapping your rear screen heater on instead of the lights or heater,as this is the heaviest electrical load next to the starter motor, if this has a similar effect I would say yes it is an alternator fault,
But i am no auto ellectrician, and alternators are very complicated, well, they are to me, so I don't really know the answer appart from replacing it or having it checked by a specialist in this field.
Good luck.

[Hymie]

No � it is unlikely to be the alternator that is at fault � although it is an electrical fault.

Your alternator is there to charge the battery; under normal conditions, with the engine running, the alternator will be putting out just under 14 Volts (to keep the battery charged). Should the alternator fail, it will normally not charge the battery and eventually the car will fail to start. It is possible for the alternator to fail such that it is outputting an excessive voltage � this will be apparent from very bright lights (with the engine running), and the battery boiling dry due to overcharge. But just in case I�m wrong, check the battery voltage with the engine running.

Now for your fault � I suspect that switching on a heavy load (lights or the heater) is interfering with the voltage from the throttle potentiometer or possibly the ECU (electronic control unit � the onboard computer controlling the engine running). It is most likely that the heavy electrical load (lights or heater) is causing a voltage drop (at the throttle potentiometer or possibly the ECU) due to a resistance which should not be in the circuit (either at a connector/switch or partially broken wire).

Without a detailed circuit diagram it is difficult to fault find such a problem � but it may be a known fault which can be easily fixed by a Suzuki garage.

[slayer921]

Thank you all for your replies! Its a great help.

Im afraid i have a soft top so I cant slap on the rear screen heater :)

I will try and find a voltmeter and check the voltage across the battery! I've had it checked and there was nothing to suggest it is boiling dry and the lights dont appear to be excessively bright! I've also tried forcing the revs down by breaking in a lower gear and they dont dim which i thought might happen if they needed higher revs to work!

I was trying to avoid paying for labour but it looks like it might be my only option! I wont cause any damage if i leave it like this for a bit will I? Doesnt seem to be a big problem! Just a mild annoyance at the moment!

[Hymie]

Your problem will be that your engine will be idling at 3,000 revs rather than 900 or so. This could make pulling away, quicker than you might want. Also, for any given gear, your minimum speed will be determined by this increased engine speed � meaning you might have to de-clutch to reduce speed.

Try looking at a few Suzuki forums for advice � someone might have posted this fault before.