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Charging system-stupid newbie question

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Ok Folks. Preliminary test results are in and I now know why there are so many pubs in the UK. In fact, I having a cold one now. The car has problems.

1.Took car to AutoZone and they tested the charging system. The battery is not charging.
2. Alt was bench tested and it passed.
3.Using Mult Meter, set to DC
-b/t batt posts, eng off, 12v
-b/t batt posts, eng on, 12v
-connected to big brown wire, B+ terminal, no volts.

FYI: Current electrical uses in car are guages, am/fm cassette, int light, high intensity headlights, the rest of ext lights are standard.
That's the latest. /ubbthreads/images/graemlins/cheers.gif
 
Let us know exactly how the alternator is wired. There should be a switched brown small gauge wire for the exciter in the alternator. I'll try to find a simple alternator diagram.
 
Big brown wire in middle and two smaller brown wires on either side of it. So technical, I know. /ubbthreads/images/graemlins/smile.gif
 
1) Were do the small brown wires go?
2) Do they have yellow tracers?
3) With the key on do either or both of the small brown wires have power?
Questions first, then answers. /ubbthreads/images/graemlins/wink.gif
 
I dont have a clue where they go but all of them are wrapped together. the wires are pretty dirty but it looks like they have yellow tracers or stripes. With key off, I have power on one. about 12v.
 
Pretty sure with the key on, both of those wires should have 12V (or a little less) on them. I think the one that's off is resistive wire so they may read 11.3V or something like that, but I'm nearly positive both should have voltage when the ignition is on.

Here's a general alternator 101 article. It's intended for jeeps but its my usual reference:

https://oljeep.com/gw/alt/edge_Alternator_Theory.html

I'm sure someone will set me straight on the details shortly.
 
Ok, with the key on does the charge warning light come on?

If it does, does the other brown / yellow wire at the alternator (the one that didn’t have power with the key off) have power? It should.

The charge warning light should have a switched white wire from the ignition switch, and a brown / yellow wire going to the alternator. When the key is on, but the car is not running, power flows from the white wire through the bulb to the brown / yellow wire and then to the alternator to provide the excitation to "kick off" the charging. (This should be the brown wire that doesn't have power on it when the key is off.) If the wiring is disconnected or the bulb is bad you will not get this excitation power. Normally in a used alternator there is enough magnetism left for the alternator to self start, but usually at a higher RPM. Since you replaced your alternator recently there may not be enough residual magnetism to self start.

Check this out and let us know.
 
Ah, disregard my comment about resistive wire then. As chris said, it has a lamp that provides the resistance on the field wire.

Good call on the bulb being out chris...
 
The charge warning light. Where is it? Is that the red one or the blue one on the dash? Is it even on the dash? The red light comes on when the car starts. I have never seen the blue one light up.
 
Red light = alternator
Blue light = Head Lamp High Beam Indicator
 
If you disconnect the brown wire that is off (when the key is off) and then turn the key on does to charge light still come on?
 
Chris, the red light comes on when I start the car for a few seconds and then goes out. How long is the red light suppose to stay on? At this point, should I open the wiring harness to see if any of the wires are bad?
 
If the light goes out that means the car is charging. When the car isn't charging the drown wire gounds through the alternator winding. As it charges the potential difference across the bulb goes to zero (simplified version since there is a diode in the circuit I believe) and the light goes out. It is odd that the light goes out but yet you are only seeing battery voltage (12V) at the alternator large brown wire terminal. I need to think about this some more.

Jeff, it sounds like you may be going to Lansing this weekend. /ubbthreads/images/graemlins/driving.gif
 
[ QUOTE ]

Jeff, it sounds like you may be going to Lansing this weekend. /ubbthreads/images/graemlins/driving.gif

[/ QUOTE ]

LOL, yea, that's a confusing one.
 
Brian - can you give us the voltage from all three wires at the alternator when the engine is running and that red light is out?
 
When I tried that last nite, I put the pos prob of the meter on each individual wire and the neg ground to the engine block, the meter stayed at zero volts.

Are these problems the norm with British wiring and those jokes are true or a myth. I'm starting to believe the jokes are very much true.

FYI: I will be at the Car Show at Fitzgerald Park in Grand Ledge MI from 8am-4pm Saturday. Taking "Murphy" to his 1st car show. Since the show is only 15 miles from my house, I can make it. Bad charging system and all. Also, I have my emergency kit; AAA road service and my cell phone.
BTW: Jeff or anyone else in the general area, if you want to experience some Lansing Hospitality, I will not stop anyone. /ubbthreads/images/graemlins/smile.gif
 
Here's a thought. Could the way the selenoid is hooked up be a possible cause? I'm not using a Lucas but a generic one purchased from AutoZone. Very similar to the Lucas.
 
wait, so with the ignition off you have 12V on one of the small wires but when the ignition is ON and the engine running they are ALL 0V?

Think that one that read 12V with the ignition off should still read 12V.

If it's reading 0V, run a new wire from that post directly to the battery positive terminal (or the appropriate post on the starter solenoid).

As for the reliability of lucas electrical systems. In the last two years, I had my hazzard switch fail & the fuel guage is intermittent. That's it. Compare that to my wife's jeep that's 20 years younger, and it's had a crank sensor, cam speed sensor, fuel pump & two bad grounds in the last 18 months.

Still seems to me that lucas is better than at least DC!
 
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