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View Full Version : sr20 low voltage, electrical guru please look at this


smithrcing17
07-03-2013, 03:57 PM
okay before everybody jumps down my throat, yes ive searched, no its not like any other thread ive found..

last year car ran perfect, all new trans and motor WS harness, tuned the car on nistune, ran perfect...

this last winter, got cage installed in car, had battery unhooked whole time, get it back voltage seems fine, take motor out, put on new turbo kit, deatschwerks 550cc injectors, same harness, 3000 miles on 80 amp alt, tore heater core out, tore radio out, only thing electrical in my cabin is the 3 aem gauge and lights, fuel pump, injectors, only electrical thing my car has is necessities. pulled all unused fuses and relays from heater and radio and such, no ac, no horn....

does have mishimoto electric fan, on relay, fused connection

so my voltage is fairly low, like 12.8 at idle... my tuner is like wtf this is not good, im like maybe its my fan? so im like okay ill get a quest alt, so I buy a new quest alt and it runs at like 13.5v idle, started to tune and voltage stays about the same spot, cranking amps drop low to like 10, but always seemed to level out at around 13.5 ish, with fan running under wot it would see high 12s... still wasn't the greatest

parked car for 3 weeks waiting on tomei 740s, didn't touch a thing on it.. come back and start it up after installing new injectors have 11.5ish volts at idle, cranking amps crazy low. mind fucked:picardfp:

pull injector harness check voltage again, nope not bad injectors. go over all 6 of the main harness grounds, two in rear, two by doors, two by headlights, go over WS harness ground, motor grounds, add two 4 gauge grounds to both sides of motor, run continuity tests on every fucking wire I can find, alt is brand new (200 miles tops), put brand new optima yellow top in, cranking amps still low, better, but low.. went back over all grounds, sanded them and made sure all tight.

nistune is reading like 10.8v ign on. put multi meter on battery at same time and its reading 12.5v????

start car, low cranking amps again, has new mishimoto starter, car idling, nistune reads mid 11s volts still, go to battery, steady 13.8v, go to alt steady 13.8+, go to starter.... same thing... nistune still reading low, back probe ecu on eccs pins and they are reading 12v instead of my 13.8ish volts that everything else is reading, ive checked every fuse, every wire inside to make sure weld slag didn't fuse two together... checked EVERYTHING! somebody please give me more suggestions.....

previous info on car:

previous owner told me car was always manual, just found out last week by searching vin it was originally a automatic, my WS harness is for a manual s13 sr20 to manual s14... but car ran perfect PERFECT all last year??

ecu is good, no check engine light or codes in nistune...

when I bought the car the driver headlight and power window didn't work because of a wire that had wore through in driver fender well, was butt connected and heat shrunk... I plan to pull fender tomorrow and double check it but harness heat shrink looks fine...

anybody with any suggestions please chime in what I could be missing....

car never sees water, rain, snow... only water it sees is from the hose and is dried immediately with a leaf blower and towel.

s13mikesr20
07-04-2013, 12:09 PM
you got a regulator anywere else besides the alternator

see if the alternator harness/starter harness has extra ground and no crap wires id start there and bigger gauge wire everywere you can think