Hi guys!

So I'm trying to find the reason for the servo alarm are beeping every other time i start my Punto Grande from 2005.
The ground cables in the engine bay are fine, new battery (52A/460CCA) but still the problems occurs..

My next step are the alternator, i measured the apmere to just around 48-55A at idle speed (around 900-100 rpm, with all the lights heater an fan on)
but i have no idea wich Rpms. i have to measure it at.

The alternator should give 70A at max, how can i be sure my alternator gives enough power?

(sorry for my poor grammar. English are not my mother tongue)

Hej Nicholai,

just wondering HOW you measured the Amps ? Normally it's done by measuring the voltage drop across a known (low ohms high watts !!) resistor. Maybe you used a clamp style Amp-meter, which I won't trust much in continuous current…

Anyway, current (amps) is one thing and voltage (volts) is another one that you have to consider too regarding the charge circuit ! The combination of both gives the power actualy delivered.

To make this understandable by non-electric familiar forumers, let's compare it to plumbery: the amps being the flow and the volts the water pressure: passing thru a given diameter pipe (resistor) the flow would have a certain value (liter per second / Amps) If the pressure increases (more volts) the flow will increase proportionnaly, same if the pipe diameter increases (lower ohms resistor): the restriction in the pipe will be less (less voltage drop) so more water will go thru at unchanged water pressure. For the same duration, more water will be drained off the tank, like more Energy (Watts, Ah) would be drained from the alternator...

With electricity, this is given by ohms's law: U=R*I, I=U/R, R=U/I with U as Volts, I as Amps and R as Ohms. Power (amount of water / Energy) is given by P=U*I or also P=R*I² if one doesn't know the voltage (U)…

Further than this, one should also consider the chemicals inside the battery: each cell will need a certain voltage (>2,1V -ish) in order to initiate the charging reaction, if the alternator can't provide enough voltage, or if it drops thru resistive connections (why I explained the whole stuff in the beginning), the electro-chemical reaction will not be sufficient to charge the battery correctly.
Note also that the battery itself can be considered as a pipe in the plumber's description: it has an internal resistance which get higher when it's worn, so it also restrict the charging Amps …

The ennemy here is probably a bad ground/internally roten cable, OR your alternator which is dying (worn brushes or a few open diodes). I'd check the Amps AND the volts to confirm …

BRs, Bernie

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Hi Bernie, Thanks for your enthusiastic and detailed answer.

Sorry i forgot the Voltage, its around 14.3V which should be fine

I'd use a clamp aperemeter but didn't' set it on max input, the 48-55A are my estimate average, but the amperemeter didn't com near 60A.
I know this device aren't the most precise, but shouldn't it give a okey estimate?

The ground in engine bay from batteri to engine at chassis are perfect, i even installed 2 more, just in case.


Do you know, are there a standard RPM to measure the amps?
and a minimum % of the generators stated amps that a generator should produce to be OK (in this case 70A)

Hi Nicholai,

the charging Amps will finally depend on how the battery was discharged OR how much current is drained by the consumers, so it's not easy to tell … 14,3 volts seems perfect BTW.
You claim the ground cables are ok, have you checked the + cables the same way ?? It comes from the alternator, goes to the starter and finally gets to the battery; if ANY connection is resistive you'd get a voltage drop and (almost) no charging ...

The alternator should provide full output at engine's 1000 RPM (ish), the regulator would decrease the excitation coil current for higher revs

BRs, Bernie

You can test alternator performance only by bench-testing it.

You cannot test max A output with the alternator still on the car (and you shouldn't add any external load)

cmosfxx said:

You can test alternator performance only by bench-testing it.

You cannot test max A output with the alternator still on the car (and you shouldn't add any external load)

Click to expand...

Agree, output Amps will depend of the load and/or battery discharge status … On a Bench test, the alternator will be connected to a (HUGE) load resistor and will be run at various speed to plot the output curves. On car test will just tell that the voltage is ok, so the gen 'should' charge the battery and at least tells tha it's not completely dead …

BRs, Bernie

If someone here helped You fix -or better, understand- your issue, hit the thanks icon @ bottom right corner, it's free and makes us feel helpy ;-)

Nicholai said:

Hi guys!

So I'm trying to find the reason for the servo alarm are beeping every other time i start my Punto

Click to expand...

What do you mean by servo alarm?

Bernievarian said:

Hi Nicholai,

the charging Amps will finally depend on how the battery was discharged OR how much current is drained by the consumers, so it's not easy to tell … 14,3 volts seems perfect BTW.

You claim the ground cables are ok, have you checked the + cables the same way ?? It comes from the alternator, goes to the starter and finally gets to the battery; if ANY connection is resistive you'd get a voltage drop and (almost) no charging ...

The alternator should provide full output at engine's 1000 RPM (ish), the regulator would decrease the excitation coil current for higher revs

BRs, Bernie

Click to expand...

I will check the + cables in the weekend, alsto the + and ground to the power steering. but when the voltage is fine, shouldn't the connections be okay?

It makes sense that the regulator will decrease the current to the battery when charges, so it won't blow up

aurick86 said:

What do you mean by servo alarm?

Click to expand...

The dashboard beeps when i start and say: 'check servo, see instructions manual' but the power steering always run smooothly
I think this problem occurs oftens when driving short distances, therefore I'm starting to test the charging system
Also if i use the electric windows or other equipment when turning the key, can force the dashboard alert

Nicholai said:

I will check the + cables in the weekend, alsto the + and ground to the power steering. but when the voltage is fine, shouldn't the connections be okay?

It makes sense that the regulator will decrease the current to the battery when charges, so it won't blow up




The dashboard beeps when i start and say: 'check servo, see instructions manual' but the power steering always run smooothly
I think this problem occurs oftens when driving short distances, therefore I'm starting to test the charging system
Also if i use the electric windows or other equipment when turning the key, can force the dashboard alert

Click to expand...

Definitely got a power (grounding/+ wiring) or battery issue. Voltage @ battery and voltage @ steering unit might be different ...