Alternator wiring Daimler 250 v8 saloon

[344739lv]

I have just picked up a new toy - nice Daimler 250 v8 saloon. All seems well apart from one thing. The car has had an alternator and negative earth conversion and the alternator is not charging the battery. Before replacing the alternator i noticed two wires hanging down behind it. One thick black and one thin black both with spayed ends.

At the back of the alternator there are 3 terminals, 1 marked ground, 1 marked and 1 not marked. No wiring is attached to the alternator.........

I can't help thinking that these two wires should be connected somehow - can anyone help?

What goes where?

Tim

[J44EAG]

Wires should most certainly be attached to the alternator. To run the unit with nothing attached may well have now blown the diode pack.

By convention, black is -ve.

On the alternator a medium red cable +ve, should run from the appropriate +ve tag to the starter +ve common stud.

If the alternator has a W marking, this goes to the windings on the unit and is often used to supply a pulse pip signal to fire an electrical rev counter if fitted to a car.

Can you see what the markings are on the alternator?

Can you see what manufacturer made the unit and what the model number is?

Perhaps then we will be able to find a circuit diagram for that particular unit. Principles are similar for most units but details may vary dependent on whether the unit has an internal or external control unit.

A typical installation is shown in this image. Double left click to enlarge image.

Mike K

[344739lv]

Mike,

I can't find a make or model but the terminals on the rear are marked, "ground", "positive" and one is unmarked.

They are three in a row - to accept spayed ends or plugs....

The two wires I have on the car with spayed ends are both black, one is thicker than the other ...... About twice as thick.

Any ideas?

Tim

[J44EAG]

Hello Tim,

This should help you. There is a good wiring diagram contained in this link together with a written section which tells of what goes to where. Easier than to describe.

http://www.tb-training.co.uk/MarineE08.html

See if it makes sense of what you see on your unit.

Mike

[ecosselynx]

Hi

As I'm traveling at the moment offer any more help other than appeal for others to lend a hand. For clarification the 250 should have some as standard with fitted with an altenator the earlier model was fitted with a dynamo.
Can anyone out there please send a copy of the 250 wiring diagram and if possible let him know which wires based on thickness go on which terminal.
Mike, you will need to try and identify the make and model of your altenator to ensure it is or at least similar to the original fitted

[J44EAG]

I`ll get on to one of our local guys who has a V8 and see if he can help with a diagram. Back to you asap on that if I get any joy.

1962 - 67 cars seem to have had a dynamo and 67-69 cars had an alternator.

In the meantime, I think it might be no bad idea to identify the key start and ignition warning lamp circuits. I have a tentative idea that the unmarked tag on the alternator may be the one that goes to the ignition lamp. Seems logical.

Mike

[344739lv]

Mike, John - really appreciate your help. I have established that it is a Lucas unit. The terminals on the back are marked ground, positive and one is unmarked. The car has clearly been driving without the unit being connected. If I connect the thicker of the black wires to the unmarked and the thinner to the positive, the ignition light comes on without the ignition being on. Clearly I haven't started the car in this format. Reversing the wires so that the thick wire goes to positive and the thin to the unmarked, no charging is enabled and the output bounces all over the place on the meter. I am simply using a tester at the Battery which shows 13.6v standing and then bounces all over the place between 0 and 7 when running. The ignition light does not come on when running. I have used the assumption that unit is already grounded as it is bolted to the engine.

Do I assume the alternator is faulty?

Tim

[J44EAG]

13.6 volts sounds high. Is that fresh off your garage battery charger?

I`me wondering if the alternator regulator might be damaged and over charging.

To my mind. one half of the diode pack could have given up if the alternator has been driven without cables being attached. Hence perhaps 0-7volts seen on the volt meter.

Mike

[smiffy]

Hi Tim
Neither of the wires connected to your alternator should be black, so the wiring must have been modified at some point. Maybe you can follow them back from the alternator to see whether they join to the originals, probably somewhere near the regulator. The thin black wire is (hopefully) connected to a brown wire with a yellow tracer that connects to the ignition warning light. The thicker black wire should be the positive feed, which should (hopefully) be connected to a thick brown wire with a white tracer, which will connect to the ammeter and ignition switch. However, the thick black wire may alternatively be connected directly to the battery positive terminal. You need to sort out the wiring as a priority before going any further.
The output connector on Lucas alternators is usually a large spade terminal, with the connection to the ignition warning light (the excitation circuit) being a standard size spade terminal. As you say, the body of the unit is earthed; I don't recall an earth connector on Lucas alternators with built-in regulators. Are you sure it is a Lucas unit?
In your original post you say "before replacing the alternator..". I presume that you mean that you thought it faulty and therefore were planning on replacing it, or did you mean something else? I suspect, from your description of its behaviour, that it is indeed faulty. It might be best to get it tested before you proceed much further.
The ammeter on these cars is rated at 30A, and may be overloaded depending on the output of your alternator.
Have you contacted the previous owner to try and get answers to your questions? I guess that he can't be too far away from you if you managed to get home on the charge in the battery. Curious that he sold the car to you without the alternator connected! Makes me more suspicious that the unit is faulty.
Happy hunting, David