So I installed a new 115 amp alternator in my SIII V12 at the beginning of the year, and ran an extra 4ga wire from the alt to the firewall positive post and an extra ground wire from the alt to chassis. All has been working fine and I've been getting right around 14 volts at idle with AC and headlamps on.

I thought I had properly secured that extra positive wire to the firewall to keep it away from the engine/manifold but at some point it came loose and was resting on the exhaust manifold. The heat burned through the outer sleeve and shorted out. I first noticed smoke from the area as I was pulling into an auto parts store close to my house. The positive battery terminal had actually come apart with the wire coming loose from the terminal. I thought that was the issue so swapped in a new + battery cable there in the parking lot. I drove the short distance home and took another look. The new battery cable was super hot so I did a quick voltage check before shutting it off and it was just 12.6v so the alternator was not charging it. I removed the air cleaner to get a better look and that's when I noticed the burned/shorted cable to the alternator.

So what are the odds I've fried the alt or anything else? The battery seems ok still. I still have the car apart as I was in the process of replacing the tray below the battery, and also reinstalling the passenger side AC blower and I want to button all that up before putting in the new alt to firewall wire and trying it. Are there any tests I should run before I give it a go? Unfortunately, this isn't the first and won't be the last self-inflicted damage I've done over the years.

 

Most of us have done that stuff. part of the learn curve!!! We learn more from mistakes than from successes!!

fix the bad wires. fire up the car. check circuits by turning stuff on, one by one. check the alternator for out put. if anything got hurt, that would be my guess.

I have my own tales of woe that I have survived the ones caused by me...

Carl

 

a bad alternator will kill the battery, and a bad battery will kill the alternator. That is what they say, unless they are just trying to sell you a new battery and a new alternator.

I have been buying used revived batteries from the local salvage yard. Under $30.00 for a revived battery and 30 days warranty. What has happened is that the revived batteries have lasted over a year so far. I am not going to spend $120.00 for a new battery.
I don't know what they do to those used batteries but they seem to have more power than a new battery.

 

If your Static battery voltage level with the key off is 12.50 volts for instance, Start vehicle and voltmeter should rise two volts approximately. Does the Battery light go out when running? Is there 12 volts at the field wire?

Larry Louton

 

Thanks for the replies and advice. I finally had time to spend some time on it today and ran a new wire and copper lugs and secured it properly and made sure everything else looked in order. Static reading of 12.47 volts. It started right up and am getting 14.1V at idle and a little higher when revving. The battery light on the dash does go out. I didn’t take it out for a run yet, but perhaps the Jaguar gods have spared me this time. I plan to charge the battery overnight as it’s usually bang on at 12.6 when sitting.

 

If you fixed all that with a new cable and a little labor perhaps your the new Jaguar god until you screw up again. Take the title just for the day please.

Thank you.

Larry Louton