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ok so battery light on so take jaguar to garage new alternator 230 pounds fitted not bad then 2 days latter light back on then told its prob because batter drained so need a new one so go get a new one 2 days light on again go back to garage diag says fault plug side alternator does this mean new wire needed ?
 

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Personally I would check the ground points as well as the alternator connector.
 

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Hi, if you could update your signature via the link below and tick Show Signature we would know which variant to reply to.


Roger
 

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Hi atkinson

If the battery checks out ok, I'm with Jimbov8 and the earth points and cables.

To make the battery light come on the alternator must be struggling to keep up,

The way I understand it, if the electrical contact surfaces become oxidised they create a resistance that puts load on the supply.

Page 22 for the earth points.

Jag electrics for x-type

It could be a main earth point. There are a few high-load earths.

The lads at the garage will probably avoid the chat and just get on with it if you've got the electics manual to point at while mentioning voltage drops.

See how that goes.
 

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It should also be mentioned that the Positive cable should also be checked as that is prone to corrode under the sleeve at the battery clamp,

Roger
 

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Having recently gone through much pain with the same issue, I have now changed...
- Alternator
- Starter Motor
- Battery
- Positive Cable
- Negative Cable

And it still kept doing it.

Then tried cleaning off the contacts on the negative cable as someone here suggested - all light problems now gone away.

Although I do know the battery was fried anyway in mine.

TMW
 

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As rchiv said, the positive cable is prone to corrosion at the battery clamp. The corrosion happens inside the crimped joint so it can go unnoticed but sometimes the cable insulation in this area becomes discoloured due to heat. If you have a multimeter and some really sharp needle pointed probes then you could try setting the meter on its lowest millivolt range then pierce the insulation about one inch down the cable from the clamp end with one probe, pushing and screwing it around to get a good contact and then getting an equally good contact with the other probe on top of the terminal post. Switch on the headlights and also get someone to operate the starter motor. If there is any reading at all on the millivolt range then you have a high resistance here and the cable will need replacing (not with a second hand one as this is a common problem and you don't want to replace one iffy cable with another iffy one).
 
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