stuTHC
24-02-2009, 21:07
<TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR vAlign=top><TD>Changing the alternator
contributed by Rich Russell
Headlights dimming when you turn up the stereo? Battery not charging? Maybe your alternator's failing....
Changing the alternator is simple, however first check that you do actually need a new one:
1) Using a voltmeter, measure the voltage at the battery whilst the engine is idling. It should be between 13.5V and 14.8V.
2) Now increase the revs to around 2000, and measure the voltage again. It should be between 13.5V and 14.8V still.
3) Turn on the headlights, foglights, rear screen heater, fan and stereo.
4) The voltage should dip, then return to between 13.5V and 14.8V. The engine note may change too.
5) Turn everything off and disconnect the voltmeter.
If this doesn't happen, the alternator is failing to generate (and keep regulated) enough voltage to run everything.
Also check that with the engine running, the voltage between the battery negative terminal and the alternator body is less than 0.25V. Any more and you've got a dodgy engine earth connection. Check the battery negative to bulkhead cable and bulkhead to gearbox cable connections are clean and tight.
Similarly, check the voltage between the battery positive and alternator positive output (the terminal nearest the engine) is less than 0.35V. C
Other symptoms of a dying alternator are the battery warning light coming on, despite the fact that the belt is tight, battery failing to charge, battery getting hot, and battery leaking liquid.
Always check the alternator belt is tight before condemning the alternator - it should be possible the move it about 1cm on the longest run (between alternator and bottom pulley).
Also check all connections are clean and not corroded.
A new alternator should cost around £65 for a recon or £120 for new. Some places may want your old alternator in exchange.
To replace the alternator:
1) Disconnect battery negative lead.
2) Disconnect the wires from the positive alternator connection (nearest engine, 10mm nut).
3) Disconnect the wires from the negative alternator connection (8mm nut).
4) Disconnect the warning lamp connector (top of alternator, brown plug).
5) Remove bolt from top of alternator, where it fixes to the adjustment rail (13mm).
6) Pull alternator away from front of car, and remove the belt from it's pulley.
7) Swing the adjustment rail upwards, out of the way (you may need to unclip the coolant hose that runs along the front of the car)
8) Swing the alternator forwards, so it's resting on the plastic shield next to the headlight.
9) Remove the other alternator bolt (13mm).
10) Remove the alternator from the car.
11) Clean up the connectors on the wires with glasspaper or a wire brush.
12) Fit the new alternator into position, and refit the lower bolt.
13) Swing the adjustment rail back into place.
14) Swing the alternator back up and slip the belt over the pulley.
15) Refit the top bolt, and push the alternator forward to get the belt tight.
16) Tighten the top bolt.
17) Connect the warning light plug.
18) Connect the negative alternator wires.
19) Connect the positive alternator wires.
20) Connect the battery negative lead.
21) Start the engine and check the belt isn't wobbling/slipping/binding.
22) Check the voltages as before, you should now be able to belt out 150dB from your subs, whilst having all the lights and heaters on, and the voltage shouldn't dip below 13.5V. </TD><!-- Spacer --><TD width=15> </TD><!-- Images --><TD width=200>https://www.rtoc.org/articles/i/Alt/sAlt.jpg (https://www.rtoc.org/articles/i/Alt/Alt.jpg)
Alternator
</TD></TR></TBODY></TABLE>
contributed by Rich Russell
Headlights dimming when you turn up the stereo? Battery not charging? Maybe your alternator's failing....
Changing the alternator is simple, however first check that you do actually need a new one:
1) Using a voltmeter, measure the voltage at the battery whilst the engine is idling. It should be between 13.5V and 14.8V.
2) Now increase the revs to around 2000, and measure the voltage again. It should be between 13.5V and 14.8V still.
3) Turn on the headlights, foglights, rear screen heater, fan and stereo.
4) The voltage should dip, then return to between 13.5V and 14.8V. The engine note may change too.
5) Turn everything off and disconnect the voltmeter.
If this doesn't happen, the alternator is failing to generate (and keep regulated) enough voltage to run everything.
Also check that with the engine running, the voltage between the battery negative terminal and the alternator body is less than 0.25V. Any more and you've got a dodgy engine earth connection. Check the battery negative to bulkhead cable and bulkhead to gearbox cable connections are clean and tight.
Similarly, check the voltage between the battery positive and alternator positive output (the terminal nearest the engine) is less than 0.35V. C
Other symptoms of a dying alternator are the battery warning light coming on, despite the fact that the belt is tight, battery failing to charge, battery getting hot, and battery leaking liquid.
Always check the alternator belt is tight before condemning the alternator - it should be possible the move it about 1cm on the longest run (between alternator and bottom pulley).
Also check all connections are clean and not corroded.
A new alternator should cost around £65 for a recon or £120 for new. Some places may want your old alternator in exchange.
To replace the alternator:
1) Disconnect battery negative lead.
2) Disconnect the wires from the positive alternator connection (nearest engine, 10mm nut).
3) Disconnect the wires from the negative alternator connection (8mm nut).
4) Disconnect the warning lamp connector (top of alternator, brown plug).
5) Remove bolt from top of alternator, where it fixes to the adjustment rail (13mm).
6) Pull alternator away from front of car, and remove the belt from it's pulley.
7) Swing the adjustment rail upwards, out of the way (you may need to unclip the coolant hose that runs along the front of the car)
8) Swing the alternator forwards, so it's resting on the plastic shield next to the headlight.
9) Remove the other alternator bolt (13mm).
10) Remove the alternator from the car.
11) Clean up the connectors on the wires with glasspaper or a wire brush.
12) Fit the new alternator into position, and refit the lower bolt.
13) Swing the adjustment rail back into place.
14) Swing the alternator back up and slip the belt over the pulley.
15) Refit the top bolt, and push the alternator forward to get the belt tight.
16) Tighten the top bolt.
17) Connect the warning light plug.
18) Connect the negative alternator wires.
19) Connect the positive alternator wires.
20) Connect the battery negative lead.
21) Start the engine and check the belt isn't wobbling/slipping/binding.
22) Check the voltages as before, you should now be able to belt out 150dB from your subs, whilst having all the lights and heaters on, and the voltage shouldn't dip below 13.5V. </TD><!-- Spacer --><TD width=15> </TD><!-- Images --><TD width=200>https://www.rtoc.org/articles/i/Alt/sAlt.jpg (https://www.rtoc.org/articles/i/Alt/Alt.jpg)
Alternator
</TD></TR></TBODY></TABLE>