Hi ,

I own a bravo 2011 t-jet 120hp

I noticed that when a high electric consumer kicks in (especially the fan+aircon) there is a slight dim in the light (for under a second).

I tested the battery with a multimeter and found out the following:

engine off- 12.79V

engine on (no consumers)- 14.2V

engine on + lights - 14.2V

engine on + lights + stereo + rear window heater- 14.1 V

engine on + all the above + air con (inc. fan)- 13V

When i rev the engine up to 2000-3000rpm it goes back up to 14.2V

any ideas?

Thank you very much

Adam

Hi, @adamag87
This is normal. From the tests you have done and voltages measured both the battery and alternator are OK. The Aircon will cause this effect because the compresssor pulley clutch is a heavy (inductive) electrical load and it takes a moment for the regulator in the alternator to respond. The fact that the compressor may also slow the engine slightly makes the effect even more noticeable.

Robert G8RPI.

g8rpi Thank you for your fast response!

Is it ok to measure 13V when the air con and fan is on?

It stays at 13V when the revs are around 800 but goes to 14.2 when i turn the revs up to 2000+

adamag87 said:

@g8rpi Thank you for your fast response!

Is it ok to measure 13V when the air con and fan is on?

It stays at 13V when the revs are around 800 but goes to 14.2 when i turn the revs up to 2000+

Click to expand...

Hi,
Yes, It is OK for the voltage to fall a little at idle under load. 13V is still higher than the off-charge battery voltage so the alternator is providing all the power for the car electrics, but it's not giving very much charge to the battery. Once the revs pick up the battery is getting a full charge.

Thank you

Normal behavior, nothing to worry about.