battery spark

[97pajman]

Hey all, Just wondering if someone could shed some light. When I connect my battery I get a spark (not huge) but when the charge wire is unplugged off the alternator it doesn't spark. Am not sure what this means. It is an 85 Hilux with a 253 in it. Thanks Guys

[clm434]

Generally caused by an electrical current lol. Theres most likely a short somewhere. Someone else on here will have a better idea.

[-Scott-]

You can get a small spark from quite small current draw, so it's not necessarily a problem.

The fact that it's not there when the charge wire is disconnected suggests that the current is something to do with the alternator, or something else connected to the alternator.

Are you having trouble with the battery going flat? Do you have something to measure the current with?

[97pajman]

I have had trouble with the battery going flat but it only happens if the ute is left sitting for a few days with it connected. Multimeter shows 12.5v with engine off and 13-14 with running.

[-Scott-]

I have had trouble with the battery going flat but it only happens if the ute is left sitting for a few days with it connected. Multimeter shows 12.5v with engine off and 13-14 with running.

Inconclusive, really. 13-14 running sounds OK, depending on actual conditions - it probably could be a little higher. 12.5V with engine off sounds lowish, depending on what the vehicle has been doing immediately before you measured.

Does your multimeter have a current mode? If you could use it to measure the current which is creating the spark, or flowing down the charge wire to the alternator, that could help us isolate the problem.

Just remember that, for measuring current, your meter goes in-line - current flows through the meter. Use the highest current setting available (to begin with.) Always hold one probe as you "make" the circuit (easier to "break" if something is wrong), and preferably have a loop of the probe wire in your hand - if it gets hot, something's wrong!

Good luck,

Scott

[97pajman]

Yeah thats what I thought, 13-14 is about normal, I will take it to tthe sparky tomorrow and get him to take a look. Did get told a while ago that the alternator was a bit doughy. Thanks for the help

[Cossie]

Mine did this at the same time I started having flat battery problems. The alternator had got tired of putting out for all those years without getting anything in return. It started getting greedy and stealing charge from my battery when the engine was off.
It was new alternator time for me as the Nissan pos is too exxy and pointless to rebuild.

[97pajman]

Went to the auto spark today, he said it is most probably a diode stuffed in it. Will get it bench tested and if it isn't worth fixing its time for a newy, probably get a newy anyway as I want to up the amps.