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It’s been a few weeks since I have had any time to work on the Stag. It’s been a very busy time at work – the culmination of 2 years work successfully delivered at the end of June 17. So now it’s time to take a breath and get back into the garage.
The last few weeks have benefited from some very warm, dry weather – perfect for the old Stag. I have had the Stag on the road a few times with the hood down listening to that intoxicating burble. But, every time I get into the car after it has stood for a few days, the battery is flat. As there is now radio or clock at the moment, then this is a little puzzling. Once started the, voltage reading climbs up to 16.5v (as I would expect if the battery was very low) but it stays there and doesn’t drop back as I would expect after 20-30 miles. Dropped a quick query on the SOC Forum and the consensus is that the alternator needs replacing. The built in regulator is probably not functioning.
The direct replacement is the 18 ACR. Some upgrade to higher ampage, but I intend to replace the lamps all round with LED so I don’t feel the need for more amps at the moment, as LED will reduce the overall load. So, courtesy of the interweb and RimmerBros a new 18 ACR arrived. Fitting from above was fairly straight forward. Moved the screen wash bottle out of the way. Disconnected the power steering pump brackets and swung the pump around to where the screen wash bottle once sat. Then slackened the 3 bolts that hold the alternator in place. Then the problem – and there always is one. The old alternator has 4 terminals and the new one only 3.
Looking at the Stag wiring diagram, the extra thin brown terminal doesn’t seem to be needed. It looks like it connects to the same general, pre-ignition switch live as the other 2 larger Browns. Checked with the SOC Forum just to be sure. The advice is to isolate it and just use the single large connector. So, put it all back together and hay-presto the alternator now responds to the level of charge in the battery – success.
A week later – battery flat again. Perhaps the over-charging old alternator had destroyed the battery? I’ve no idea how old the battery is. I’ve probably fried it. So, down to Halfords to pick up a HCB072 calcium battery. Maybe this would fix it. Well it did for a week or so. Then the same problem – flat battery after a few days.
Putting an ammeter in series with the battery positive lead showed 2.5A without the key even in the ignition!! Something seriously wrong here.
So back to the wiring diagram. By following each of the paths from the battery positive, I found that the current was leaking through the Ignition Warning lamp via the alternator to ground. The internal resistance of the alternator circuitry was luckily preventing a dead-short and the flames that usually go with this. So why was this happening? Another painstaking but systematic tracing of wires followed. As always, when I found the problem it was easily explainable. The 2 thin wires from the alternator (one brown and one brown/yellow) exited the alternator, into the loom, then popped out of the loom further along the engine component into 2 bullet terminals and a double connector. The wires had been reversed into the connector: brown to brown/yellow and vice versa.
I’ve replaced the connector with new individual bullet connections which I have heat shrunk. An easy mistake to make. The brown and brown/yellow look very similar especially when covered in the gunk from the engine bay, but the problems it has probably caused go further than the ones I have found so far. There is evidence of fiddling with the console warning cluster and internal lighting. But those are problems for another day.