Disco alternator in a 300tdi Defender

[Ranga]

I have it on good authority that MR Auto use a Discovery alternator as a defualt replacement for dead Defender alternators.

What's the advantage/s?

[justinc]

I always replace the original defender 65A one with the Disco 100A one, too Ranga:)

JC

[Ranga]

I always replace the original defender 65A one with the Disco 100A one, too Ranga:)

JC

Yeh, but why? :confused:

[justinc]

100Amp vs 65A, and they are rebuildable IE the bearings are replaceable. The Defender units use the end of the rotor shaft as a bearing surface, which means when the rear needle roller bearing fails it takes the whole rotor with it, costing the same as a new alternator....At least bearings etc are cheap for the Disco version.
And they are 100Amp output, not 65Amp.

JC

[Robmacca]

Gents,
Bringing an old thread back to life - I'm in the process of swapping over my dead Defender ALT with a Disco 100amp one.
Now, on the Defender ALT there is the H/D cable wire for charging the batteries, etc and the only other wire (Yellow with brown strip)

The Disco 100amp ALT has 3 wires


The H/D wire for charging batteries
Yellow and Brown strip wire
White with black strip wire


I've measured the volts on my other car (Disco Tdi) to check what voltages there are at the Disco ALT as follows


Yellow and Brown strip wire - approx 7v when engine running at idle
White with black strip wire - approx 13.5v when engine running at idle


My question is with this conversion - how do u wire the Disco ALT into the Defender when the Defender only has the H/D Charge wire + the Yellow/brown strip wires? What do I do with the 3rd Terminal where the White/Black strip is connected to on the Disco?

Also, with engine off on the Disco, the only wire with 12v is the H/D one, the other 2 wires a not alive with engine OFF & they are also not alive with the ignition ON, they are only alive when engine is running.....

Can anyone help us with some advice as to how to wire these Disco ALTs into a Defender?

[Richo130]

Ok, being an auto elec I might be able to help. On the alternator the 3 wires are 1, 12v. 2, warning light or battery light. 3, tacho output. I will go and take a photo of the back of mine to help

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[Richo130]

Hope this helps.

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[Richo130]

The red wire is my tacho, brown with yellow is warning light, and the one with 3 cables is the main battery post.

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[dero]

I did the same on my 97 Def. just ignore the tach wire

[Robmacca]

Cool, thanks for that.... Is there some way of utilising this spare term to install a tachometer on the defender?

[Richo130]

Absolutely. It is a direct feed for a tacho. Basically run a wire from the "w" terminal on the alternator to a tacho. I would recommend a vdo universal tacho with a cylinder selection switch. I did this and replaced the clock in the instrument cluster. Bridge an ignition and earth supply from the guage next to it and your done. Now being an alternator feed tacho it will not be 100% accurate but it will be pretty close (within a few 100 revs). If you do want a dead accurate tacho you will need to purchase an alternator feed tacho. The only one I know of is made by cole hersee but they are super expensive. Personally, I couldn't justify the cost. If you need anything else let me know. Also if you're in Melbourne you are more than welcome to look at my setup.

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[Robmacca]

Absolutely. It is a direct feed for a tacho. Basically run a wire from the "w" terminal on the alternator to a tacho. I would recommend a vdo universal tacho with a cylinder selection switch. I did this and replaced the clock in the instrument cluster. Bridge an ignition and earth supply from the guage next to it and your done. Now being an alternator feed tacho it will not be 100% accurate but it will be pretty close (within a few 100 revs). If you do want a dead accurate tacho you will need to purchase an alternator feed tacho. The only one I know of is made by cole hersee but they are super expensive. Personally, I couldn't justify the cost. If you need anything else let me know. Also if you're in Melbourne you are more than welcome to look at my setup.

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Cheers for that..... Yes, thought that there maybe a little bit of inaccuracy due to the different size pulleys