NSW Corvettes

Technical Tips => Electrical-Electronics-Air-Lighting-Guages-Security-Vacuum => Topic started by: 87droptop on May 03, 2011, 10:08:29 PM

Title: Battery gone flat AGAIN
Post by: 87droptop on May 03, 2011, 10:08:29 PM: Hi All,
since i installed the thermo fan and electric pump I had a problem of alternator not keeping up with these and other electricals and charging the 470amp battery, so it ran a bit warmer than usual since fan was not pumping fully ( 1968) , and eventually it cut off the fuel pump and stalled... I got a 85amp alternator rebuilt ( the other one was 30-40 amp), got a 680amp battery, went for drive, this time it lasted about an hour, so i thought all is ok, and then, sure enough, it died again, so tow truck it home... not happy... battery was flat, again. I might need check all wiring if i can get my hands on a wiring diagram... and, has anyone had any similar issues? maybe i can sort this out soon and turn up at the bankstown show on may 15...
Thanks Guys.
Title: Battery gone flat AGAIN
Post by: Scott on May 04, 2011, 08:21:23 AM: Grab a multimeter and check the voltage at the battery and alternator to see if it's charging when the engine is running. If the voltage at the alternator is different from the battery by much, something is wrong. The voltage at the battery should also be higher when the engine is running, compared to when the engine is off.

It sounds like it's not charging, which could mean a bad connection somewhere.
Title: Battery gone flat AGAIN
Post by: bfit on May 04, 2011, 09:58:14 AM: Voltage at the battery should be 12.7 minimum
with the engine running
Take engine from idle to about 3500/4000 voltage should vary up a little but not to high 13v to 13.2v approx

then turn the lights on high beam, thermos on as well
and check again you can get an idea how the alternator is working under load

look for hot joint this indicates a bad connection
and extra Resistance will reduce alternator efficiency

hot joint can result in a fire and that is real worry

I would suggest a battery isolation switch I think every vehicle should have one

It is a good Idea to check all your earth straps
Bfit
Title: Battery gone flat AGAIN
Post by: 77CVT on May 04, 2011, 02:36:19 PM: :agree: Hot joints = bad news!

Easy test is to start it, put all the lights\accessories on and disconnect the positive battery cable. If it dies, coughs, lights dim etc the alternator isn't up to it.
Title: Battery gone flat AGAIN
Post by: sirfixalot on May 04, 2011, 10:17:52 PM: As the load current is increased battery voltage will decrease if alternator is not charging. What year wiring diagram?