Well a dc motor is a resistor... no back EMF or none of that nonsense... so I see it as if it has reduced voltage and the same resistance then I=V/R than its current draw reduces greatly, even if the battery can provide 300-500cca the motor will draw whatever current determined by the potential difference across the winding...

In saying that when you measure the battery unloaded you'd see 12 or more volts (car not running) when you crank it I wouldn't be surprised if the battery drops as low as 9V due to the load... (Voltage regulation is never perfect, the more load the more the voltage drops, esp with a battery, did get taught this at tech, but can't remember how to work it out now...)

Will be interesting to see if a battery fixes it... But sounds too bizarre to me...

Got a Supercharge 600 CCA sealed calcium battery today 3yr warranty. Car starts and runs as it should.

The old battery was starting too fail under load??,
Float Voltage was still 12.34Volts but noticed this morning when starting the car it dropped really low on the voltage under 11volts. It's Never gone that low before..

The new battery starts the engine quicker and the voltage holds steady at 12volts while cranking.

Last edited by EL___Fairmont on Thu Oct 21, 2010 11:47 pm, edited 2 times in total.

there you go I do stand corrected...

But still can't my head around why it was doing what it was doing...

At least its fixed now anyway...

Cheers,
Tim

Hi tim,

After 2 weeks with the new battery the car started doing the same thing losing voltage when headlights & a/c were on. Then the car would stumble really bad in the mornings and sit at about 400rpm cold and 600rpm when warm at idle.

Tracked it down via good old gregory's manual and a multimeter. Pin 25 ISC reference was 0v or 2.5v should be 11v-8v depending on engine load. Removed my 6DJA tickford ECU and installed the stock ecu and it's running better than ever. BTW I tried another ISC solenoid of me parts car first--thought it may have got jammed...

Cheers.. Hopefully it's just the Capacitors in the ecu that need replacing...cheap fix..