Reply With QuoteA bad earth on something that is only active under high load...
Electrical gurus: How can my charging system be doing this?
OK, so i've been battling with an electrical charging system issue in in my AE71 since the 1JZGTE conversion. Basically when under load, the system voltage drops to 11.5 volts as it comes onto boost around 3500rpm, then settles at a still low 12.7 volts to redline. Any other time when cruising, idle, etc the alternator happily cranks out a steady 14.00 volts.
I can't replicate the problem by free-revving the engine whilst stationery, it only happens under load.
I'm running the factory 1JZ alternator, with wiring customised to suit (was originally external reg with the 4AC engine), this wiring has not changed since my previous 4AGTE conversion which worked perfectly.
I have tried two alternators with exactly the same result, so that can be eliminated.
Any ideas? Throw anything my way, i've tried many things already but will happily listen to any suggestion no matter how trivial it may seem, as i'm going insane chasing my tail at the moment!
Cheers
Phil
AE71 Corolla 2 door window van - retired / JZA70 Supra - VVTi converted - sold
Re: Electrical gurus: How can my charging system be doing this?
A bad earth on something that is only active under high load...
I am the sun
Re: Electrical gurus: How can my charging system be doing this?
belt slip?
Re: Electrical gurus: How can my charging system be doing this?
running a dedicated wire from the alt to the battery? running a dedicated earth lead from alt housing to battery?
check earths from block.
check that bolts from alt to bracket to block are tight and there is electrical contact...
etc
"I'm a Teaspoon, not a mechanic"
"There is hardly anything in the world that a man can not make a little worse and sell a little cheaper" - John Ruskin (1819 - 1900)
AU$TRALIA... come and stay and PAY and PAY!!! The moral high horse of the world!
Re: Electrical gurus: How can my charging system be doing this?
Adding another earth lead never hurt nobody... Several times I've seen earthing that looks like it should be fine just not doing the job at all times, but add another one and all is fine.
Re: Electrical gurus: How can my charging system be doing this?
check tightness of all wiring connections,especially earths, it could be that as the engine moves on its mounts under load, a connection may separate or partially separate and give you a lower charge rate.
Re: Electrical gurus: How can my charging system be doing this?
and cleanliness of the earth points..
or one of the field diodes might be failing (could happen in 2.. ya never know)
scope the output? or get an LED voltage monitor thingy from jaycar?
"I'm a Teaspoon, not a mechanic"
"There is hardly anything in the world that a man can not make a little worse and sell a little cheaper" - John Ruskin (1819 - 1900)
AU$TRALIA... come and stay and PAY and PAY!!! The moral high horse of the world!
Re: Electrical gurus: How can my charging system be doing this?
Sounds silly but is the old external reg still in there somewhere?
Edit: judging by what ive seen of your engine bay i doubt it is
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Re: Electrical gurus: How can my charging system be doing this?
I agree you have a Earth problem .... Id say around the injector area check the harness earth to the intake runners ...
Keith:
Re: Electrical gurus: How can my charging system be doing this?
whoa, thanks for the quick replies!
Bad earths: unlikely, i've checked all connections and added two extra earthing points to clean bosses on the chassis
Belt slip: Possibly, although i'd imagine the belt would have to be slipping savagely for the alternator to spin that slowly that is puts out practically no charge. There's no signs of slippage on the belt either.
Battery is located behind the passenger seat, terminates at the starter motor, same place where dual 6mm cables connect from there to the alternator.
The motor moves very little under load, the JZ is on stiff mounts. I have driven the car with a digital multimeter connected directly to the battery with a passenger monitoring the voltage, plus the voltage readout on the ECU handset confirms the same.
External reg is somewhere in landfill, nowhere near my engine bay
Keep 'em coming!
Cheers
AE71 Corolla 2 door window van - retired / JZA70 Supra - VVTi converted - sold
Re: Electrical gurus: How can my charging system be doing this?
Hmmm a relocated battery
Keith:
Re: Electrical gurus: How can my charging system be doing this?
Huh? You mean like directly from the body of the alternator all the way back to the battery?Originally Posted by KGB
Hmmm a relocated battery
Keith:
AE71 Corolla 2 door window van - retired / JZA70 Supra - VVTi converted - sold
Re: Electrical gurus: How can my charging system be doing this?
yup 10 chars
also look for anything which might move backward during accel (ie, boost), and see if anything can short..
does it happen on the dyno?
"I'm a Teaspoon, not a mechanic"
"There is hardly anything in the world that a man can not make a little worse and sell a little cheaper" - John Ruskin (1819 - 1900)
AU$TRALIA... come and stay and PAY and PAY!!! The moral high horse of the world!
Re: Electrical gurus: How can my charging system be doing this?
it might be worth putting the multimeter on the IGN and Batt pins while doing a 'boost run' to moniter their voltages. if either drops lower then the actual battery voltage then youll have a problem. then again if the BATT pin decreases, the alternator output will increase.
anyhow check the IGN pin for continuous 12v.
might be also worth checking the tightness of the +ve pole nut on the alternator (sounds silly i know!)
hello
Re: Electrical gurus: How can my charging system be doing this?
and you may want to also consider that the voltage drop is caused by a large current draw (ie short). cranking usually drops the voltage to about 10v so it would have to be a short on one of the thicker unfused wires
hello
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