3tgte idle poor with electrical load

[oldcorollas]

sounds like you are on the right track!

[pauljones1976]

Ok, well with the -ve terminal on the battery strapped straight to the engine block (and front of the chassis) I'm still getting huge voltage drop when the lights & brake lights are all on at idle - it dropped below 12v at one point) so I'm going to rule out a bad earth.

I know it happens when the thermo fan comes on too, so to me it all points to not enough power at this stage.

Brendan, yes the distribution point accepts +12v from the battery terminal from the boot and redirects it out from there. There are two bosch relays which send power here and there and to be honest, I don't like the look of the connections underneath. Plus I wonder if there really is enough contact to carry good current. I was really hoping I didn't need to fiddle with them, as I wasn't game to figure out where all the leads were going and why. I guess there's no real choice now though!

I really do suspect the microtech just cannot deal with the drop in voltage and it's cutting spark or something causing the engine to miss and lose rev's, causing more drop in voltage. That's what appears to be happening when you watch the readout on the multimeter, it dips and then pops back up over 12.5V once it get's close to 800rpm again.

Does this sound like a fair assumption?

[oldcorollas]

yup ,all sounds reasonable.

if you up the idle to say, 1500 first then 2000, does the voltage drop still?
if not, then the alt is spinning too slowly.

what is idle speed?

do you get the same voltage when measuring from battery terminals, as you do from say, IGN power and earth on block? if so, then the wiring is not issue, just the alt.

[pauljones1976]

Well, after figuring out the Microtech handset I can finally now see the voltage inside the cabin At 2000+ rpm I still get voltage drop but not anywhere near as much as at idle. So the Alt is charging. However, with the lights all running and brake light on, stereo, it is borderline. If I turn on the blower up to full it just can't handle the load and stalls (even at 3000+rpm which is odd. I suspect the Alt just isn't that flash and I'm seriously considering putting the old 3tgte one back in place of the 85A bosch. But I just might buy a brand new bosch instead.

I'm thinking I might have a combo problem going on here - the alt is not spinning fast enough at idle & there is something odd happening with the earth (or somewhere else in the wiring).

So I might look into higher than 85A Alts - I've heard that the higher the output (150A+) you get a fairly high output at idle which is ideal. With a slightly smaller pulley I might just have the output I want at idle. The car isn't being raced, it's purely street use and I don't really rev it past 5000 anyway so I don't have too much concern about over-spinning the Alt at high rpm.

Seems a bit odd that I need so much power at idle though; I really don't understand how I'm getting so much loss just from having the battery in the boot - does your average street car really rely so heavily on the battery at idle? Is that why we don't have so much trouble when the battery is in the engine compartment rather than the boot?

My intention is to get the car to a point where it is usable of a night, the noise is bearable for long periods of time, and it doesn't stink of fuel all the time. Having a wife and two kids means you don't get much 'daytime' use and getting it to behave and be relatively comfortable of a night would transform the car into a usable piece of machinery!