Alternator
From Holdenpaedia
Original submission by T:
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[edit] Alternator:
[edit] Alternator Upgrades:
Note that increasing the size of the Alternator Feed Wire is vital if a larger Alternator is to be fitted to the Car. The cable must be capable of carrying the maximum rated output current of the Alternator or the wire will heat up, burn and begin to starve the car of current which will result in a full or partially discharged Battery. If the Alternator is reated at 85 amps, the cable must be capable of carrying sustained 85 amps.
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Using a heavy duty Fan Belt will improve the Engine's ability to rotate the Alternator and avoid Belt Slip.
[edit] The Sense Wire:
This draws 0.120 milliamps which is a very small amount of current. You can connect this Wire directly to the Battery +ve Terminal for best results. Some people connect it to the B+ Terminal on the Alternator because it's easy to do. Other People connect it to the Ignition Circuit so that it doesn't draw Curent when the Engine is turned off.
[edit] 2 Watt Bulb:
The warning light used with a Bosch 85 Amp Alternator should not exceed 2 Watts.I found this out the hard way, the alternator I have I bought new years ago and it was fitted in my HJ for several years with no problems. When I fitted it to my HQ the regulator failed shortly after, I replaced the regulator and modified the dash light and the problem is solved.
I think it's worth noting in the paedia, I'll get you a photo of the 5 watt bulb for reference.
Cheers
David
[edit] Fitting a VN V8 85 Amp Alternator to an Old Holden:
The V8 85 Amp Alternator is easier to fit than the V6 85 Amp Alternator.Make sure the proper sized fan is fitted to the Alternator because the large one will strike on the Alternator Upper Bracket.
If fitting it to a straight 6, make sure that the Regulator Connector is on the nearside or the Alternator will jam up against the exhaust manifold. You will need to remove the Rear of the Alternator, rotate it and refit it the proper way around.
When you upgrade to a higher capacity Alternator you will have to upgrade the Alternator feed
to match it.
| Alternator Connection | Description | 85 Amp Alternator Connections |
| S | Sense | Connects to either the Battery +ve or the Alternator's B+ Output |
| I | Indicator | Connects to the original brown coloured Wire from the Indicator Light. |
[edit] Chassis Ground Cable:
The Chassis Ground Cable carries all the return Current that doesn't go through the Starter. Light, Radio, Wipers, Internal Fans Thermo Fans all send their return Current through the Chassis Ground Cable.
Make sure the Chassis Ground Cable is large enough to carry all the Electrical Load except the Starter Current.
I recommend using a seperate length of Starter Cable connected between the Chassis and the Engine Ground Cable to make sure the return Current does not cause a large Voltage drop or burn any Wires.
[edit] Operation:
Alternators consist of a Rotating Electromagnetic Field (called a Rotor)and a Stationary set of Coils (called the Stator). The Centreshaft contains the Rotor
and the Stator is mounted in the Alternator's Casing.
[edit] Regulator:
A Regulator controls the current entering the Rotor. The greater the RotorCurrent, the more power the Alternator produces. It is the job of the Voltage Regulator to maintain the Alternator's Rated Output Voltage provided the RPM is high enough to produce the required load current and its maximum Current Output is not exceeded.
[edit] Alternator and Regulator Operation:
The Regulator turns the Field ON when the Indicator Voltage is less than 14 Voltsand turns the Field OFF when it is more than 14 Volts. It normally does this so fast that you cannot see it.
The Wire connected to the Right Hand Brush goes Blue when the Regulator has turned the Field ON and Red when it's turned OFF.
The average of the Regulator ON and OFF times produces the current required by the loads switched on at the time. In this way, the alternator output continually matches the load, and keeps the system voltage at the desired 14 Volts at the Output Terminal provided the Alternator is connected to a Battery.
If an Alternator is run without a Battery it can produce lethal voltages. While the average Voltage may still be 14 v, the peak Voltage can be as high as 100 volts.
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[edit] The Regulator's Circuit:
Each Transistor changes colour to Blue when it is turned ON and Black when it is turned OFF. Blue means that current is flowing through it, Black means that no current is flowing through it.The heart of the Regulator is the Zener Diode. It only turns ON when the Indicator Wire Voltage exceeds 14 Volts. Once the Zener has turned ON, it turns ON the Left-Hand Transistor (called the Driver Transistor). When the Driver Transistor turns ON it turns OFF the Right-Hand Transistor (called the Power Transistor). When the Power Transistor is OFF it prevents current from flowing through the Field Windings.
When the Indicator Wire Voltage is less than 14 Volts, the Zener Diode turns OFF which turns OFF the Driver Transistor. When the Driver Transistor turns OFF it turns ON the Power Transistor.
When the Power Transistor is ON it permits current to flow through the Field Windings.
The two Capactors apply Positive Feedback to the Driver Transistor ensuring that it stays OFF or ON when it is required to be that way.
The single large Diode connected between the two Brushes arrests the High Voltage Kickback from the Field when the Regulator turns off. Without this Diode the excessive voltage from the Field would destroy the Regulator.
[edit] Cut-Out Relay:
No Cut-Out Relay is used because the Internal Diodes prevent the Battery's currentfrom flowing into the Alternator when it is not producing power.
[edit] Current Regulator:
No Current Regulator is needed with an Alternator because the device will automaticallycurrent limit when the Rotor's Magnetic Flux is exceeded.
Once the maximum current output of the Alternator is reached it will go into Current Limiting.
At this point both the output Voltage and Current will be reduced.
[edit] Load Response:
You can expect a 14.2 volt 85 amp Alternator fully loaded or unloaded to supply 14.2 volts up to and including 85 amps. It's the job of the Regulator to ensure that the voltage remains as constant as possible within its current range (0 - 85 amps) provided the RPM is high enough.
[edit] Reliability:
Alternators wear out brushes and bearings which will need to be replaced periodically.[edit] Efficiency:
Bosch Alternators are particularly efficient and can deliver when the Revs are down low but other makes of Alternator may only deliver when the RPM is quite high.Some Alternators have a "sense" connection. This connection is made directly to the battery. In the situation where a Battery is placed a long way from the Alternator the "sense" wire fools the Alternator into producing Extra Voltage at its output to cover any losses in the long Alternator Feed.
As a result the Alternator might be producing 16 volts at its Output Terminal while the Battery is receiving only 14 volts.
[edit] Alternator Failures:
[edit] Low or no voltage:
Eventually the Brushes will wear out. This is characterised by a lag in voltage, evident on a Voltmeter. On some Alternators the Brushes are part of the Electronic Regulator and replacing the Brushes and Electronic Regulator together makes good sense. Internal components of the Electronic Regulator can be effected by heat, go out of tolerance and cause the Alternator to output a higher than Rated Voltage.Worn Brushes can also cause the charge light to stay on after an "*off the key start" but go out when the RPM is increased.
(* An off the key Start requires no Throttle or Choke. You simply turn the Key to the Start position without touching anything else).
When replacing Brushes the Alternator will not get back to full efficiency until the Brushes
have the contour of the Slip-Rings matched to 100%. It may take a few days for the new Brushes to bed in.
Provided the Slip-Rings (the Copper Rings that the Brushes connect to) aren't worn down too far the Brushes can be replaced, otherwise new Slip-Rings will have to be fitted or the Rotor Shaft replaced.
[edit] Overvolt or excessive voltage:
If the Output Voltage is in excess of that stamped on the Alternator, it's likely that the Regulator has failed. In the case of an Electronic Unit, replacement is the only option.
[edit] Worn bearings:
The Alternator's Bearings will eventually wear out. Symptoms are excessive End-Float, Side Clearance and rumbling while the Rotor Shaft is rotating.
[edit] Alternator Tips:
[edit] Belt Alignment:
Make sure the Alternator Pulley is in perfect alignment with the Harmonic Balancer (the Crankshaft Pulley). If not the Harmonic Balancer will flex and cause a vibration as the Engine revs up. Flex of the Harmonic Balancer will eventually cause the destruction of the Balancer.[edit] Protection From Entering Contaminants:
If performing any work on the Cooling System, cover the Alternator with a cloth. Any Coolant that gets inside the Alternator can cause an internal short likely to blow the Regulator and or Diodes or short out the Stator Windings.
[edit] Fan Belt Tension:
Fan Belts shrink when they get hot so it's best to check or make any adjustments to the Fan Belt Tension when the Engine is hot otherwise excessive tension will be placed on the Bearings resulting in a failed Alternator and/or broken Fan Belt when the Fan Belt heats up.In cold weather Fan Belts grow longer and slip causing the Alternator to charge less. The looseness
can also wear out the Belt rapidly. Retensioning the Belt in winter may be necessary.
The Fanbelt will develop a squeal caused by a flat spot that gets polished everytime it passes the driving Pulley. The squeal tells you the Belt needs retensioning and perhaps even replacing.
[edit] High Capacity Alternators:
An 85 amp, or higher, Alternator makes great sense. It will recharge the battery faster, carry the car's electrical load more effectively and handle the transients provided by electric motors and aggressive ignitions better.It's important to match the Battery type to the Alternator.
[edit] Monitoring Alternator Operation:
A Dash Mounted Voltmeter is invaluable for monitoring the Alternator since the driver gets instant indication of certain problems or problem patterns.
[edit] Broken Rotor Wire:
Early HQ alternators used to break a wire that ran from the sliprings to the rotor windings because insufficient glue was placed
on them.
Centrifugal force used to place excessive stress on the wire
and make it break.
Resoldering the broken wire and better gluing fixed them.
[edit] Troubleshooting:
[edit] How To Locate Gen Light Wire:
Use a Brake Light Bulb to ground a Wire you think may be the Gen or Ind Light.Push the Sleeve of the Bulb against a clean Earth Point and connect the Wire to the Bulb's Contact.
The Gen Light will illuminate because its Resistance is much higher than the Brake Light Bulbs.
Using the Bulb will prevent any other device from being blown when the connection to Earth is made because the Current Flow will be safely reduced.
[edit] Interchanged Sense and Indicator Connections:
My Battery goes flat and there is a buzzing noise under the bonnet when the Engine is turned off.
The Sense and Indicator wires on the Alternator have been reversed. The Sense Wire goes to the Battery +ve and the Indicator Wire goes to the dash charge light.
[edit] Bosch 85 Amp Alternator Break/Fix:
The Alternator stopped charging in the UC last night.
A check showed the Charge light wasn't coming on which meant no excitation for the Rotor.
A while back on the forum the view became that the charge light
was not necessary for a Bosch 85 amp Alternator because they can self excite. I couldn't make mine self excite no matter how high the revs.
After driving the 20kms home at night, the 6 year old 530 CCA Delco Battery didn't have enough charge left in it to push over
even one piston on an attempted start.
On working the problem this morning I removed the connector from the Alternator and shorted the L (charge/indicator) line to chassis. The Charge light still didn't come on with the ignition so that ruled out the Regulator being the cause of the problem. I removed the Instrument Cluster and cleaned the Charge light contacts and it started glowing when the Ignition became active again.
An attempted start showed the Battery had recovered sufficiently overnight (without any charging) to perform an easy and successful cold start.
The Alternator started charging perfectly again.
T
[edit] Loss of Excitation Workaround:
However just after writing the above story i got fed up with relying on the instrument light and wired in a switch which i press in for a second which exites the alternator. Maybe we could put something about putting a switch in on the holdenpedia site.
Use Dick Smith diode catalogue number Z3229 (10 amps, 1000 volt Peak Inverse Voltage). This diode is overkill but is not likely to blow on you.
[edit] Links:
TIP2955 Transistor Connection Info
BXH1236A Wiring. Use D+ for Gen Light. Info provided by GraemeG.
[edit] Terms:
TermsBack to Electrical Index
