Alternator Off Car Testing

Alternator is a device which converts ac to dc cause it is of no use directly for the battery.  In alternator off car test we took the alternator and DISMANTLED it in the following way

• Removed the nut on Terminal and insulator
• Removed the 3 nuts that hold the rear cover, remove the rear cover
• Removed the brush holder and voltage regulator
• Removed the 4 screws that hold the rectifier, remove the rectifier

we then did the Rotor Winding to Ground Test in this we set the multimeter on 2K then placed the black lead on the centre of the rotor shaft. Placed the red lead on slip ring. There should be no circuit in between these points so the spec was infinty and it was found to be infinity so it was alright.
Then we did the rotor winding internal resistance. We set the meter on 200 ohms, tested the internal meter resistance by touching the 2 leads together. Remember that the internal resistance of the meter must be taken away from the actual reading. Place one end of each lead on the slip rings as indicated to obtain reading. The reading specification is 2ohm to 6 ohm. The readings came out to be 2.9 ohms so it fall between the spec so it passed the test.
Then we did tested the stator winding  resistance. We set the meter at 200 ohms  and then testwed the internal resisitance of the meter.Then we selected tbhe common terminal of the stator winding terminals A to D. Connect the black lead to the common point. Connect the red lead to the other terminal one after the another and record their their resistance they should be approximately the same from 0.0 ohm to 0.2 ohm
All the readins were between the spec so it passed. Then we ste the meter at 2k. Placed the red lead of the meter on the common stator winding terminal and the black lead of the meter on the body of  alternator. There should be no circuit between the staotr winding and ground. The meter should read infinity and if there is a circuit then the stator has grounded  and requires replacement
Then we tested the rectifier positive diodes. We set the meter on diode test mode. Put the common lead onB terminal. Then touch the positive lead on each of the P terminals and record the reading. The resistance should be low. Place the positive lead on B terminal. Then touch the common lead on each of the P terminals and record the readings. The resistance should be high.
Then we did the Rectifier Negative Diodes. We set the meter on doide test mode. Put the common lead on E terminal. Then touch the common lead on each of the P terminals and record the readings.
Then we checked the brush protusion length.In this we used a vernier calliper it should have been over 4mm and one was but the other one wasnt.
After all these tests i could say that the alternaotr passed the rotor winding to the ground test. the internal resisitance of the rotor winding was also ok so it passed. The positive diodes of the rectifier had some problem cause they failed the testand while testing the negative it was ok so it passed the test. The voltage regulator was also working alright.When we checked the brush protusion then we found that 1 was alright and the other one was bit short and needed replacement

Relay

A relay is the device which uses a low ampereage circuit to switch on a higher amperage circuit.This is very common among vehicles and they are of various kinds but do the same sort of work.
First of all we measured resistance of the relay from
86 to 85 was 76.4 ohm
30 to 87a was 0 ohm
30 to 87 was 0 ohm
then we had to identify the the controling circuit and switching circuit.
the 86 to 85 is the contorlling circuit and 30,87and 87a r switching cause the resistance is bet 86 and 85
in a relay when the relay is off 30 to 87a is NORMALLY CLOSED and 30 to 87 is NORMALLY OPEN
then we made a circuit using a relay 3 bulbs and a 12v source in sucha way that all 3 r in parallel and when we turn the realy on the bulbs r on.

Then we made a circuit in whcih 2 bulbs were in parallel and 1 in series adn the relay alternatly turns them on off.

Battery Testing

The make of the battery was LUCCAS and its number was 127ME. The battery capacity in cold cranking amps was 550. It was a conventional battery.We were able to get to the elctrolyte by unscrewing the screws.Then we carried out the visual checks. The terminals were clean and tight. There was no sign of swelling of battery (overcharging) .The battery looked appropriate except that there should have been a bracket to hold the battery.
Then we unscrewed the battery and checked the elctrolyte levels because if the level of electrolyte would have been less than the battery wont work properly ie niether charge nor supply voltage accurately.
Then we did the OCV test before performing the OCV tests there is a surface charge on the plates of the battery which is the excess voltage that cant be held over a period of time and is produced by charging of the battery. We removed the surface charge by turning the headlights for some time while the voltmeter was connected across the battery.Then by using a voltmeter of range DC volts we found that the voltage was 12.4v
The state of charge for 12.4 v was found to be 50% so it was ok to continue thebattery testing cause charge on the bat was enough. If the battery would have been too discharged then we would have waited for sometime for the battery to charge for sometime and then perform the load test.
Then we did the specific gravity test of the battery by using a hydrometer. Hydrometer tells us the rel density of electrolyte as compared to water. If the rel density is found to be more than 1.2 then the elctrolyte is alright otherwise  if it is nearly equal to 1 then the battery is not ok
Then by using the hydrometer we checked the reading of the electrolyte and it was found to be alright and the lectrolye was clear and so the elcetolyte was perfect.
Then we did the high rate discharge test.
We used a load tester to do the test.we applied 155amps current for less than 15 secs and the voltage should hold above 9.2v . We attched the Load tester across the terminals of the battery and applied the load for 15 secs. The current was found to be 275 amps and voltage was 10.2 V so the battery passed both the tests.
This showed that the battery was in perfect shape and there was nothng needed to be done to the battery

Alternator On Car testing

I did my test on a Mazda 323 1985. First we checked wether the warning light operates or not so that if theres any problem we can knw abt it then all the accesories were turned off so that while carrying any test related to the battery the accesories doesnot lose there memory. Then we carrie dout visual checks to see if there was any lose connection  or wire. We also checked the alternator mounting that wether it was alright or not.
     Then we did a no load test on the battery. In this test the engine was turned OFF. We connected the voltmeter across the terminals of the battery it was found to be 12.5V. the voltage was perfect as to doany sorts of test battery must heave atleast 12.4V cause at 12.4 V the state of charge is 50% which is essential. Then we turned the engine on while the voltmeter was attached across the terminals of the battery . Then we let the reading of voltmeter rise till it stops rising . It was found out to be 14.7V and amp output was 7.2 A
Then we did the Load Test on the alternator. The spec for this test was OCV + .5 Volts. This is beacuse when the car is onand theres load as well then battery needs to provide voltage to support the load as well.
Then we switched on the accesories of the car and then we measured the voltage under load.
It was found to be less than that of the spec this meant that the battery is not able to provide enough voltage to support the load.

Then we did the voltage drop test.In this the enginge should be runnign at around 1500 revs And all accesories except vipers and stereo must be on.
Then we checked the voltage drop between following points

• battery positive terminal and alternator output ( Spec 0.2 V )
• battery negative and alternator body ( Spec 0.2 V )

All the tests clarified that the battery was alright but the only problem was that it was not providing enough voltage to support the load

Resistors

First we took 6 resistors of diff value then we determined the value of each in 2 ways

• COLOUR CODING
• BY USING A MULTIMETER

We took 6 resistors of different values one by one and then by using a colour coding chart we did it.
Then we took each resisotr individually and then measured the resistanc eof each by multimeter and was found to be very close to the colour coding values

Then we took 2 different reistors and measured there individual resistances and then joined them in parallel and series one by one and measured the resistance of each one.This demonstrated the principles of elctricity which were that when the resistors are connected in series the resistanc of circuit increases and when connected in paralel it decreases.

Diode Testing

Doide is a device which allows current to flow in one direction and stops current flow in the other direction.
In this test first we take a diode and mark the anode and cathode on it. This is done because if we join the diode in the opposite direction then it would short the circuit as the gate doesnot allow electricity to pass through it.
  Then we measured the resistance of the diode using a meter setting it on 2k ohm. We found that it was infinity both the ways. Then we checked the voltage supplied at the meter probes in ohm position with another meter set on DC volts we found that that it was .6 volts so the voltage acroos the meter was ess to push the binding layer of the diode so thats why we got the resistance of diode infinity. So this meant that the ohm measurement didnt work caus eit gave the same reading both ways.
      Then we did the Diode Test. It gave the following reading :-

• Anode to Cathode: 0.53 v
• Cathode to Anode: infinity

These readings meant that the diode allows the current to flow only in 1 direction only.




    Then we built a simple circuit with a diode and a resistor of 1K ohm and a 12v supply. We measured the voltage drop across resistance was 12.74v and across was .64v the current flowing through the diode is .34A. This meant that the circuit was proper cause the sum of  voltage drop across the resistor and diode is equal to the voltage supplied.and the circuit was series.
  Next we changed the resistor and used a high resistance oneand then we measured the voltage drop across resistance and diode  and the current flowing through it was 1.28 A . This showed that this circuit was also proper cause the sum of voltage drop across the dioide and resistance was equal to the voltage supplied.This also showed that the increase in resistance increases the flow of electrons ie current .
Then we took a LED. We did diode test on it and from Anode to Cathode it was 1.9 v and the other way round was infinity. The voltage drop in LED is more than that of Diode as the LED takes more voltage to start working.
Next we build a circuit with LED and a res of 1K ohm. we then measured the voltage drop across Rand d and was equal to the voltage supplied.
This all showed the all the 3 series circuits made were alright as the voltage drop across the circuit was equal  to the suppy and LED has more voltage drop then Diode

Starter Motor on Car Testing

Starter motor is that component of car as the name suggests which turns the engine of car On.
Starter motor usually have the following components in it but they may vary over the make of car and model :-
1 Armature
2 Field coils and pole shoes
3 Housing or Body
4 Brushes
5 Bushes
6 Starter Drive
There are 3 Type of Starters :-

• Inertia
• Pre-engage
• Gear reduction

In the Starter motor on car testing we require the following resources :-

• a suitable vehicle with a pre-engage starter motor
• a digital multimeter
• a clamp type ammeter with range up to 400 amps DC

The car on which i did the test was a Mazda 323 1989 model.
It was a manual transmission and there were no device on the car which required a power source for its memory. If there was any device which required a power source for its memory then we would have connected a 9 Volt battery in the cigarette lighter slot.

Then before carrying out starter circuit voltage drop tests we performed a Preliminary test in which we did the following steps :-

• De-activated the ignition or fuel injection system
• Checked the battery for serviceability
• Was the write range of meter selected or not
• Was the vehicle's transmission in neutral

Then we checked the Open Circuit Voltage across the terminal and it was found to be 12.4 v
if the voltage is 12.4 then % of charge is 50%
if voltage is 12.5v then % of charge is 75%
if voltage is 12.6v then % of charge is 95%
if voltage is 12.7v then % of charge is 100%
Open Circuit Voltage should fall between 12.4v and 12.6v.

Then we checked the available voltage across the battery terminal while cranking the cranking voltage spec is > 9.5 v and the cranking voltage achieved was 11.4v. If battery fails the cranking voltage test then the battery is rested so that it can gain some charge before continuing with this test.

Then we proceeded to check the starter circuit for voltage drop test.
In this test we needed a voltmeter and by using the voltmeter we checked the voltage drop across battery and the starter.
1 We checked the loss between battery positive post and solenoid starter input stud while cranking.
The spec for this test was 0.20v and i got 0.20v.
2 We checked the loss across solenoid main input and output terminal studs while cranking.
The spec for this was 0.1v and i got 0.1v.
3 We checked the loss between battery negative and starter motor body while cranking.
The spec for this was 0.2v and i got 0.1v

Then we added the total voltage drop across all the 3 and the spec for it was 0.5v and i got 0.4v.

Then we did the starter motor current draw test

In this test we require a Inductive ammeter (clamp meter)

The clamp meter set it at 400 amps DC and then push the Zero Button to zero the meter, if the reading doesnt Zero push the Hold Button and repeat the procedure.Once the meter is Zeroed pick up the meter and clamp around the positive battery lead anywhere between the positive terminal and the solenoid. Then with the help of someone the engine is cranked and then we get the reading on the clamp meter.
The starter should draw current between 125amps and 175amps but i got 96amps.
After all the test I conducted on the Battery i found that the battery was in good condition iit passed all the tests except the Starter motor current draw.