Correct RRC Alternator Output

**Skiboy** · 9th April 2016, 09:42 PM

I have an alternator that only seems to want to put out 13 volts when truck revved up.

On idle can sit about 12.6 v charge (digital charge gauge)

I remember being told there was some trick to setting up a RRC alternator correctly to charge at 13.5-14 volts

Does anyone know what I mean/able to give advice.

Auto Elec set this alt up - Was the alt off either a RRC or a stage one (using a stage one wiring harness).

**PhilipA** · 10th April 2016, 07:46 AM

No tricks I know of.

It would help if you told us whether it was a Bosch , Lucas , Or Magnetti Marelli alternator and which model it is fitted to.

Some alternators need battery sensing, so need an extra wire to the battery, and some Bosch alternators need a higher wattage IGN bulb. But battery sensing would be quite obvious as it would be nothing, nothing then charge

Sounds like the alternator is faulty.
Regards Philip A

**Blknight.aus** · 10th April 2016, 09:34 AM

some regulators have an adjustment screw to fine tune the output, you might also have the wrong wattage bulb or resistance in the sense line, too low and the alternator charges low, too high and it goes high.

where are you measuring the voltage from? its also possible to have the alternator putting out the right voltage because its taking its sense voltage from somewhere that is at the right voltage but between where you are measuring and the alternator exists a high resistance connection causing an apparent voltage drop.

**Skiboy** · 10th April 2016, 05:20 PM

Originally Posted by Blknight.aus

some regulators have an adjustment screw to fine tune the output, you might also have the wrong wattage bulb or resistance in the sense line, too low and the alternator charges low, too high and it goes high.

where are you measuring the voltage from? its also possible to have the alternator putting out the right voltage because its taking its sense voltage from somewhere that is at the right voltage but between where you are measuring and the alternator exists a high resistance connection causing an apparent voltage drop.

Thanks

I have a voltage digital device linked directly to the two batteries - give same reading as the volt meter in dash - Protector brand or something like that.

The digital device is there to monitor the two batteries in truck

Alt is a Bosch as per attached photo
Dash is standard stage one dash and wiring loom. According to stage one/series manual the alt should charger at 14 volts same as RRC

So doubt the bulb but can look at it.

**Blknight.aus** · 10th April 2016, 07:13 PM

get the voltage straight off of the back of the alternator.

the electrical circuit for the charging system has the ability to put the proper voltage on the electrics but not on the battery.

while you are there...

MAke up a table, with the following column titles
engine off load off, engine off load on, engine idle load off, engine idle load on, engine 1500RPM load off, engine 1500rpm load on.
4 rows
DCvoltage (cold)
AC voltage
Frequency count. (if your meter has this function, if not just repeat the DCV test)
DCvoltage (hot)

for your test procedure wait 5 minutes between each run with just the head lights and park lights on low beam to take of any surface charge.
for the final run, take the vehicle for at least a 10 minute drive to make sure the engine and alternator is definately up to normal operating temperature

what this test is looking for is any AC ripple that indicates you have a failing diode or a drop in voltage as the alternator gets hot.

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