Thread: an odd thing has started happening

hello learned and clever people,

the last couple of days, out of the blue, when I start Moriarty, 300tdi (ish) 1998 disco manual, the battery warning light stays on and the rev counter doesn't work, blip the throttle a couple of times and all is back to happy, is it a charging issue and the rev counter is another symptom or do I have a loose connection somewhere to track down?

any ideas gratefully recieved, don't want to have to shell out for a new altermator if I don't need to

Oh, and Moriarty has dual batteries.

thanks as always

The battery light operates on the alternator putting out more than 12v and stopping current flowing through the bulb.
The rev counter works off a pole on the alternator, with the pulses causing the needle to move.

For both to occur at the same time suggests an alternator output voltage issue, so I'd start by putting a meter on the battery before start and expect to see 12 to 13v . Then ideally have someone else start it and you examine the voltage.

A drop while cranking is expected, but anything lower than about 11v (I think, from memory) is worrying for battery condition. Then observe the voltage which should be coming from the alternator.
If the voltage is 14 to 15v then the alternator is putting out enough, if < 14v then I think you have to look further at why not.
If higher than 15v by more than 1v then the voltage regulator is suspect and needs to be sorted out ASAP as it can ramp to 17+ and start to cook things.

If the alternator output is low but sorts with a blip then I'd start by looking at the bushes. The battery causes the alt to excite, which could be an issue if that part is not right, but I can't recall if blipping can get it to the point where it will self excite due to residual magnetism.

Bushes should be about $30 and are easy to change, just a couple of bolts, you may not even have to take off the alternator.