Rb25det Overcharging And Cutting Out

[25C35]

Hey all,

recently joined up to the forums.

My car has been overcharging pretty bad lately and it has also been cutting out which i think could be due to this overcharging.

The car is a c35 laurel with a s1 rb25det, fairly standard motor, has :

fmic

2.5" exhaust straight through

greddy knock off ffp

hdi ebc

battery relocated to boot

its been cutting out randomly, doesnt matter what revs or if its under load etc, and then sometimes is a prick to start again like the batterys dead but other times comes back to life straight away while the cars still rolling.

it had been overcharging really bad, around 15.5, so i changed the alternator and it was still cutting out and overcharging. i also put in a mates alternator that was working fine when in his car but when in my car it is still overcharging and cutting.

ive grounded the battery in my boot to the chassis and added another ground wire to the alternator, i also put my battery back under the engine bay to see if my relocating had done something but alas it was still doin all the same things.

Anyone have any ideas at all to what my car could be doin and how to fix it?

cheers

[t_revz]

check the voltage at the alternator compared to the voltage at battery. if the alternator doesnt have a good connection to battery it will overcharge. you would see this as 11-12v at battery while 15 at alternator as an example. measure between alternator + and battery + and this will tell you voltdrop from front to rear

[25C35]

check the voltage at the alternator compared to the voltage at battery. if the alternator doesnt have a good connection to battery it will overcharge. you would see this as 11-12v at battery while 15 at alternator as an example. measure between alternator + and battery + and this will tell you voltdrop from front to rear

cheers for the reply man.

i also measured it at the back of the alternator and it was also 15.5v, the same as the battery. something else i did was unplug the plug that goes into the side of the alternator and the reading was 12.6(ish)v then when i plug it back in the cars revs drop and the alternator starts charging at 15.5 again

[t_revz]

the plug in the alternator will have a wire for the warning light and to excite the alternator to charge. with the plug off the voltage will drop because its not actually charging and just reading battery voltage. i mostly work on heavy mining gear and my alternator hasnt had a drama so im not exactly sure how its wired up but i do remember seeing a slightly heavy white wire going through that plug plus another smaller wire, maybe unplug it without engine going and see if voltage at the terminals matches the batt voltage. my first reaction would be to say replace alternator but as you have done that already its unlikely. just one more thing is to make sure the multimeter your using is ok. compare charging rate on a known ok car compared to yours. if you have to use it in the meantime drive with headlighs etc on to help prevent cutting out

[25C35]

the plug in the alternator will have a wire for the warning light and to excite the alternator to charge. with the plug off the voltage will drop because its not actually charging and just reading battery voltage. i mostly work on heavy mining gear and my alternator hasnt had a drama so im not exactly sure how its wired up but i do remember seeing a slightly heavy white wire going through that plug plus another smaller wire, maybe unplug it without engine going and see if voltage at the terminals matches the batt voltage. my first reaction would be to say replace alternator but as you have done that already its unlikely. just one more thing is to make sure the multimeter your using is ok. compare charging rate on a known ok car compared to yours. if you have to use it in the meantime drive with headlighs etc on to help prevent cutting out

checked the plug voltage and its the same as the battery.

ive tried the multimeter on a few other cars around my house and thats all good.

Ahh sweet as, ill try the headlights when im driving and see if that prevents the cutting.

thanks.

[t_revz]

checked the plug voltage and its the same as the battery.

ive tried the multimeter on a few other cars around my house and thats all good.

Ahh sweet as, ill try the headlights when im driving and see if that prevents the cutting.

thanks.

realise this is a bandaid solution to keep you going for a bit longer til its sorted and it will still possibly cut out. something still sounds fishy...what about using jumper leads from alternator to another battery prefereably not conected in a car incase it blows up your mates car haha. this will eliminate without a doubt the alternator and batt are well connected. if it still over charges i would say either look at taking it to a sparky to have a look or pull the alternator off and take it to a auto sparky shop and get em to run it up on the test bench and see what its doing. sorry i cant be more helpful. maybe there is an Sau auto sparky in your area who works for beer...

[DVS JEZ]

external voltage regulator?

[paulr33]

when did it first start, whats changed recently

my GTST was fine for years and then all of a sudden the battery light stayed on and i have 15+ volts

after many things tried inc new alternator, swap over, reco etc the auto elec found a fuse in the was missing (no idea how).

he replaced that and problem solved. dont know what fuse either. but i have seen someone else with the same issue

[t_revz]

external voltage regulator?

not for the last 30 yrs or so. internal ftw

very interested about a blown fuse causing this. would love feedback if thats the cause

[25C35]

have checked all the fuses and none were blown, both in the engine bay fuse box and the fuse box buy the drivers kick panel.

however some fuses where missing but they had A/T on the panel so im geusing they conrolled something when it was auto.

also there was one fuse that had a 15 in it when it should of had a 10 so i took it out and replaced it with a 10 then when i put my car on ign it blew straight away then i realised i must of put a 15 in there as a quick fix to get to work the next morning when i installed my fans ages ago.

Nothing has changed electricaly recently, the only thing i have done since before this all started is put the standard throttle body back on but ive put the 80mm TB back on to see if any cutting out still happens.

the piping leading up to my throttle body is 2.25 then goes to 3" just before the throttle body so i thort some sort of turbalnce or bottle necking couldve had something to do with it? probably not but it didnt do it this bad and this often before.

Im going to put all the fuses back in to what there supposed to be and check over everything again.

cheers

[paulr33]

i have no idea how a missing fuse causes it to happen all of a sudden, but it did

have seen it on another ECR33, same issue, high voltage all of a sudden, changed heaps of crap, then i found the thread, told them about the missing fuse

and they found a missing fuse, put it in and problem solved

the fuse was in the boot

[paulr33]

here it is

http://www.skylinesaustralia.com/forums/Ne...html&st=20#

[fib]

Interesting. Whereabouts in the boot is this fuse?

[paulr33]

theres a stack of them frmo memory next to the battery

a series of fuses and relays

[25C35]

thanks alot paulr33,

been looking through my boot n=but doesnt look like the c35 laurels have any fuses in the boot.

do you remember what kind of fuse it was? was it a large one or just a small blade fuse?

cheers

[paulr33]

no idea

auto elec did it a few years ago

[t_revz]

wish my car was back together so i could test... just wondering if a blown fuse could cause this then you would likely see a power loss to the plug in the alternator. you said earlier you had batt voltage there but on both terminals or only 1? maybe if only 1 then there is a fuse somewhere or open circuit wire...

[25C35]

ive only got battery voltage on the one wire, the other is for the warning light so im told and shouldnt have any power through it anyway.

i took the plug off today and put on a wire that was known 12v and was good and when i started again it shot up to 15.5v again and the wire i put on had 14.8v goin through it.

could this overcharging have anything to do with the cut im having tho?

cheers

[t_revz]

im guessing the cut is related.. did turning on headlights etc delay the cut? if so it must be related. the wire for the warning light works different on each regulator. sometimes power from cab and the power made by alternator cancels itself out to turn off light.. it was just an idea as paul said it could be fuse related. i dont wanna tell you dodgy stuff to try but i would be trying all sorts of wiring combos if i was sure it was wiring drama as i would be desparate haha. check your mates car that you borrowed alternator from and see what is at the plug...actually a light bulb just lit up. not sure if it effects skylines but sometimes if warning light is wrong wattage can cause a drama...havent fitted new globes recently??

[25C35]

put fuses in places where it was missing fuses and the overcharging is now gone.

however the cut was still there, i finally got a hold of a mates AFM and plugged it in just before and it went all good.

The weird thing is tho, i put my afm on his car and it seemed to go better with the one off my car.

i then put my afm back on my car (no pod filter as that was how his was running for the test on my m8s car) and it went fine until i revved it out in 2nd and it felt like it wasnt goin anywhere, then in 3rd gear it wouldnt rev over 4 grand, had my foot to the floor and it running fine no coughing or farting but just wouldnt go over 4k, then the car just didnt want to run properly after that.

any ideas any1???