Hi All, Ill try and explain this as good as possible but it is starting to give me a headache - Vehicle - GU Patrol, with RB30 Turbo Conversion. I had my alternator (Hitachi 12V 60AMP) rebuilt about 4 months ago as it died, once rebuilt i put it back in the car and was running a high 15.4 volts.. didnt have any issues at the time as i was running vacuum advanced dizzy. Alternator had to be revved to 3000rpm to activate though and then would charge. 2 weeks ago i changed my dizzy to a VL Electronic Dizzy (New), Ice Ignition System (New), and already had an ICE Coil. The car starts and works fine after all this change but now when altenator engages after 3000rpm the entire car starts idling funny i cant rev the car and misfires on idle. I pulled out the multimeter and this was my finding - While Problem Occuring (Alternator Engaged) - At Battery - Between 13.5V - 14.8 Coil Positive - 14.8 Coil Negative - Playing up from 14.8V down to 9V as car misfires on idle. At Altenator - Varies from 13 - 14V right through to 16+ Volts I have tried another Coil, Ignition Unit and Distributor which i know are working on mates car as we have same setup. Only difference he has GQ RB30 Turbo and Mines GU. Mates Alternator stars charging once he starts his car doesn't need to be revved. That same Alternator in my car has to be revved 3000rpm to start charging. I have contacted the guy from ICE Ignition he is saying his units work fine up to 16V as they also come with boosters to make it go up to 16V.. I don't know if they start failing after 16V OR the Crank Angle Sensor inside the distributor cant handle the high voltage. (does anyone know what there rated to??) If i unplug the battery cable from the alternator so it stop charging the car will work fine for hours until the battery dies, so obviously its got something to do with the fact my alternator is over charging but i am not sure how to stop this. My Alternator also had 12 month warranty but the place i got it rebuilt has now shutdown and the workers have moved to Ford so cant take it back. But either way a working alternator from mates car also does the same thing so i am stuck for ideas on what to check and how I can reduce it from overcharging. Feel free to ask question and i will try answer. If there is any Auto Elecs out there please help. Cheers, Ozzie

Haha, I think this is the first time I've heard of an RB30 with OVER voltage problems. Volts at the alternator look good, like brand new good. I'll try to remember to check the coil terminal specs for you tonight. Some original photos have not been recovered yet.

Check your sense wire going to the alternator. I'd bet theres an issue there. If the alternator does not see what the Battery is at, it'll charge its head off. I had this issue with an LS1 recently. Sense wire wasn't connected correctly so alternator went as hard as it could (14.8 - 15.2V!) the entire time the engine was on. Ended up burning out the alternator. Rigged up a seperate wire direct from battery (via ignition controlled relay) to the Voltage sense on the alternator. No more issues.

I am going to do that tonight. The 2 wires from the plug have been told to send directly to battery positive. One is sense wire and the other is your dash light i assume or a constant 12V. Hopefully this will fix the problem but i think i have done this already. If I am not successful do i assume the alternator reg is faulty. ---------- Post added 20-09-11 at 19:28 ---------- I joined the 2 plug wires directly to battery and now the alternator is charging without having to rev the car past 3000rpm. Now when the motor is idling its fine but go to accelerate the car start missing etc.. i am assuming this is timing/dizzy/CAS related now?? any suggestions.

Here is another update from Today - Overnight i left the battery sense wire & 12V write etc on positive terminal and it drained my battery overnight from the plug.. obviously these should be wired to ignition wire when properly done. Anyway, i charged the battery today and everything was working great again at about 14V and holding just great, alternator would start charging right away and car would be revving fine etc when cold. Once the car reached running temps, it then started idling funny and couldn't accelerate etc due to misfires. All the voltages were still fine from alternator & battery, but the voltage on coil was a bit strange. Coil + was holding about 14V but coil negative was going up and down as the misfiring was occuring. This varied from 9V - 14V as per my first post. The other thing i also played with was the crank angle sensor loom to my ice ignition unit. As i move this (plug side near dizzy) the car would stutter more etc which i though was weird. These are my next steps i am going to try (feel free to add more suggestions) - - I have my mates Dizzy which i know is working, with the same timing my car is running, so i will give that a go. It may be the optic disc inside the dizzy getting hot and metal expanding causing it to not work correctly. OR CAS is faulty even though its new and i put it in there myself. Unless over voltage from my alternator which was previous problem caused it to fail. But then it should not work at all rather than just when its HOT. Other than that i have driven my car around for ages with alternator not connected and at normal running temps the issue does not occur. So then that cancels out the dizzy again, unless the extra voltage causes it to heat more inside.. (can it be possible?) - The loom provided by ICE may have a problem, which i can try another loom from my mate as we have same setup, and yes his is working. Yet again, the question is why only when it is HOT running temp. - Disconnect the alternator from battery again while problem is occurring (HOT Vehicle) to see if it will fix itself. If it does, then i'm stuck for suggestions again because the voltages around the car are fine now. All the loom and wires etc are all placed away from heat sources so i do not know why this is occurring.