Trace alternator wiring

[Roy_S]

Getting the Stag back and working after a long rest in the garage..... I've moved the alternator up top after fitting an external water pump.
Noticed that the battery is not charging but also the IGN light does not come on before starting.
Checked the three wires at the alternator, the large brown wires are live, smaller wire nothing. As part of the move I made a new loom for the 2 large brown wires and these go to the starter solenoid and on to the battery. The smaller wire I extended running a new wire behind the bulkhead sound proofing round tho the new alternator position.
I've tested back to where I connected to this small alternator wire, no breaks but also no voltage their either.
Dropped out the dash light cluster, checked all the bulbs and they are ok.
Connected a tester to the small alternater wire and buzzed round the connector from the back of the dash light cluster and nothing, so appears to be a disconnect. I also saw that the common power to the IGN light also powers the choke light and this works, so the 12v gets to the dash light cluster and therfore being common the IGN light but no further.

I ran out of light this evening, but tomorrow I want to trace from the dash light cluster connector through to the alternator. Are there any connectors on that route, from what I could see in the limited space having removed the 4 screws and pulled the dash forward it seems to go straight into a loom.

I didn't check yet but this small wire to the alternator looks to be all brown, but it's difficult to see, I assume this brown wire should go all the way up to the dash light cluster connector and I can check the wire colour there tomorrow. The wiring diagram shows there is probably a yellow line on it, I'll check.

The route from the IGN light to the alternator shows 2 circles I've arrowed, 1 small one (green arrow) I assume to be the connector to the dash light cluster, but the second larger one (red arrow) with a line through it, does this mean another connector? and if so where is that?
Satag1.JPG

[sujitroy]

All the dash stuff is fed by a wire that does have 1 connector . The connector could be on top of the or around the heater matrix. Maybe remove the speaker grill and you may see something there.
One test. Supply 12 volts to the small alternator wire yellow brown to the bulb, the bulb should glow. You already tested the bulb but, but did you test it in the holder?
Sujit

[Roy_S]

Thanks for the reply Sujit.
I removed all the bulbs and cleaned them and then tested in the holder to make sure they were connecting. I'll drop out the speaker grill tomorrow then I can trace each way from there, I could be lucky and it's a poor connection there. If not then I'll look to run a new cable to the alternator from that connector.

[KOY 23]

One test. Supply 12 volts to the small alternator wire yellow brown to the bulb, the bulb should glow. You already tested the bulb but, but did you test it in the holder?
Sujit

How will that work? The bulb is fed 12v by the white wire, feeding 12v to the brown with yellow trace wire will not make it light, earthing it at the alternator end will and is the easiest way to check the wiring.

The thin brown wire is only used on battery sensed alternator, which has a separate Lucar connection on rear, tape up thin brown wire if no connection present.

it’s a brown/ yellow wire, not the other way round, a crucial difference.

There is a 2 pin connector for the thin wires below the washer bottle.

[Roy_S]

Interesting you mention those 2 wires under the washer bottle, one of them went to the alternator before I moved it, but what is the other for?
Wiring diagram shows 3 brown wires and the sense wire, Lucas alternator uses 2 large brown wires and this sense wire.

[KOY 23]

The connector has the 2 thin wires, brown /yellow is the warning light wire and the brown is the battery sensing wire to the alternator, if required, which it appears you don’t.
It’s vital that the warning light wire (which you call sense wire) is connected back to the brown/ yellow wire in the 2 pin connector.

[sujitroy]

Someone reported that his ignition light in the dash was always on. He later found that that there was a short between the yellow / brown wire and thick brown wire in the alternator plug. When he fixed that, his light went out. The thick brown wires supplies 12 v directly from the battery by a large black connector near the alternator.
In this case the light is not coming on at all so there could be a break somewhere along the line. As you mentioned, just by the alternator there is another black plug for wires. Roy should try that. To check if the line is OK, remove the plug and directly connect 12 volts to it. Or jump a small wire from the thick brown wire to the thin yellow/brown wire feeding the ignition light. Check that the light comes on.
For the alternator to charge the battery, it needs that bulb.


Sujit

[trunt]

How will that work? The bulb is fed 12v by the white wire, feeding 12v to the brown with yellow trace wire will not make it light, earthing it at the alternator end will and is the easiest way to check the wiring.

Koy is right on both counts, it needs a ground at the brown yellow to turn the ign light on, and it’s a great way to test that circuit.

[KOY 23]

Someone reported that his ignition light in the dash was always on. He later found that that there was a short between the yellow / brown wire and thick brown wire in the alternator plug. When he fixed that, his light went out. The thick brown wires supplies 12 v directly from the battery by a large black connector near the alternator.
In this case the light is not coming on at all so there could be a break somewhere along the line. As you mentioned, just by the alternator there is another black plug for wires. Roy should try that. To check if the line is OK, remove the plug and directly connect 12 volts to it. Or jump a small wire from the thick brown wire to the thin yellow/brown wire feeding the ignition light. Check that the light comes on.
For the alternator to charge the battery, it needs that bulb.


Sujit

Completely different scenario as the light was always on, i.e. with the ignition OFF.

Roy’s problem is that with the ignition ON the light is not working and the alternator is not charging.

Suggest you read post #4 again as your method will not work.

p.s. it took me over 1/2 hour to compose the 3 lines as I dozed off midway.

[Roy_S]

Thanks all for the feedback.
I'll hopefully get a chance to check this again tonight, my alternator only had the three wires connected before I moved it. I'm sure the IGN light came on the first time I started it, was only later when sitting in the car warming it up I noticed the battery voltage was showing low between 11v-12v that made me check.
Hope this is just a poor connection for this brown/yellow wire, it's difficult to see colours as at some point in the past they undersealed the underneth and engine bay so everything has a nice protective coating. The second wire is terminated with a crimp connector and just sitting there, so when sorted I'll cover with some heat shrink.

[Roy_S]

FIXED
Many thanks for the pictures "piacerre" they helped me find the connectors and trace the wires and all was good except for the last section out into the engine bay.
Thinking I might have ti run a new wire I decided to cut the bullet connector off the brown/yellow wire in case the crimp was only on the outer insulation, it wasn't but in the daylight I could see the copper strands were very dark. when I cut and crimped the wire originally I did it in the garage with not much light, in daylight you could see the wire was oxidised.

Cleaned strands with wet & dry, and it buzzed through to the dash light cluster, tinned with solder and fitted a new crimp and put all the dash and wiring back together.
Not had a chance to run the engine yet as due to rain it was pushed back into the garage.
Stag lights.JPG