Another bloody bodge.

Whilst fitting a new alternator to the 90 I dug up this ****-poor excuse of a wiring bundle:



I'm having charging issues - old alternator gave up ghost, new one is only chucking 11.87v into the battery. I'm guessing the ####ed up wiring is causing issues, the main charge wire is nice heavy gauge out of the alternator and is then bodged onto two much lighter gauge wires that between them aren't anywhere near the gauge of what they should be. The D+ and W terminals are bridged together (the white and brown wires in the picture above the inlet manifold), but otherwise they go nowhere - the charge light doesn't work. There is a brown wire with yellow stripes that runs with the wiring along the injector side of the engine, under the thermostat housing and then is loose with a bit of insulation tape covering it - I suspect this is the charge light wire.

I know I need to replace the ####ed up wiring and especially get some heavy gauge wire for the main charge wire, but would that be the only reason for the charge not reaching the battery? The belt and tensioner are almost new.

Cheers

The charge light circuit needs to be operating (exciter wire), otherwise the alternator will not charge.

There is no harm in using multiple wires instead of a single thicker wire, as long as the thinner wires are collectively rated satisfactorily. Parts of the factory loom are actually like this.

Ok. I'll take a punt on the truncated brown/yellow wire being the exciter wire, do the W and D connections need bridging? I thought the D terminal on the alternator was for a rev counter (which the 90 doesn't have), so is there any need for it?

The exciter wire will be skinny. It connects to the small D terminal. On mine it's white with a red trace. The + or B terminal (it will be the biggest terminal) may well have more than one connection to it, these will be the thickest wires (to the battery). Ignore the W terminal, it's for a rev counter.

Just looking at your picture on my laptop (was on phone before and could not see properly). It looks to me like the original loom has been extended. The white wire which looks like it's extended with brown wire (WTF!) will be the exciter. The two thin brown wires which are connected to the thick brown wire will be for the B terminal.

If the originals are long enough, I would cut off the extensions and re-terminate them neatly if I was you.

The white and brown wires are the W and D terminal feeds just looped to one another. They don't actually feed anything. As its a 300Tdi from a Disco I suspect the dual brown wire feed is from the original 19J engine, and the single thick wire from the Disco loom. The white and brown wires are also from the Disco, and the brown/yellow wire to nowhere the exciter feed from the 19J loom. So, if I can work out which of the white/brown wires is the exciter and which is the rev feed, connecting the brown/yellow to the appropriate wire should give me 14.4ish v at the battery..... Right?

Sounds about right. The one that comes around the thermo housing will be the exciter. If you don't have a rev counter, there should be no wire for it.

Bustrucket said:

The white and brown wires are the W and D terminal feeds just looped to one another. They don't actually feed anything. As its a 300Tdi from a Disco I suspect the dual brown wire feed is from the original 19J engine, and the single thick wire from the Disco loom. The white and brown wires are also from the Disco, and the brown/yellow wire to nowhere the exciter feed from the 19J loom. So, if I can work out which of the white/brown wires is the exciter and which is the rev feed, connecting the brown/yellow to the appropriate wire should give me 14.4ish v at the battery..... Right?

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sounds right. if they are wired up correctly dash side, then when you turn on the ignition it will send power down the batt lamp to the exciter wire. So you can either use a multi to see which spits out current, or earth the wire and the dash lamp should come on.

Sorted. Insulated the white wire, joined the brown to the brown/yellow, battery lamp works for the first time since I bought it and 14.7v is the charge at the battery

Cheers

Bustrucket said:

Sorted. Insulated the white wire, joined the brown to the brown/yellow, battery lamp works for the first time since I bought it and 14.7v is the charge at the battery

Cheers

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keep an eye on that. it shouldn't go up more than 14.4. if the regs on the way out it might start to slide up overcharging more.

i'd get the multi out every month and have a check. if it stays at 14.7.. fine tis a little high. if it creeps up anymore then replace the alts regulator.

I will keep checking, however the battery had also just come off a full 12hr charge indoors so I wonder if that skewed the reading slightly. Where is the regulator?

Bustrucket said:

I will keep checking, however the battery had also just come off a full 12hr charge indoors so I wonder if that skewed the reading slightly. Where is the regulator?

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back of the alt, you can pick new uns up so you don't have to replace the entire alt. yeah maybe it was due to the trickle charge. i wouldn't be overly concerned, just keep an eye on it long term.

Whole alternator is new so it shouldn't need replacement!

****sticks. Tried to start the 90 this morning and the battery was almost completely flat. It was given a 12hr charge yesterday, fired up car once to check alternator wiring was fixed, then all switched off. Nothing was left on overnight.

Bollocks.

stick your multi to amps.

turn everything off. discon the battery pos and stick the multi probes one to the batt pos term and the other to the pos wire you just took off. So your multi is in series with them.

check the parasitic load. if it is 1amp + then start pulling fuses one by one till it drops. then see what circuit that fuse protected.

do not start the engine or cause a large power drain, your multi will not be able to cope and will blow it's fuse.

post back

Ok will do - thanks for the advice!

Also, give your battery a good charge and get it load tested for free at a garage or Halfords. If your alternator has not been charging it properly for some time, the battery could be damaged.

No current draw at all - given that there are no electrics on (not even a clock on my 90) this sounds about right (although I did expect maybe a slight parasitic loss somewhere). There is power in the battery (enough to operate ignition lamps) but the indicator lens reckons that it needs charging (the red 'replace battery' light isn't lit).

Will charge it and have it drop-tested, but I suspect its new battery time.

New battery fitted, old battery on charge, will have it drop-tested in the week. New one isn't showing any amp loss either, will wait and see tomorrow morning if it fails to start.

Bustrucket said:

New battery fitted, old battery on charge, will have it drop-tested in the week. New one isn't showing any amp loss either, will wait and see tomorrow morning if it fails to start.

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post back if you run into any probs. we'll get there eventually