ELD & ALTC

ELD, ALTC, and U
by mattminerDOTcom » Thu Apr 05, 2007 10:56 pm

So, Ive been looking into the differenced between USDM and JDM ecus and one of the major ones is the lack of ELD and ALT on the JDM ecus.

So i started looking into what these actually are. Ill start with a summary of what each does.

ELD: this is an amneter in your fusebox. it tells the ecu what sort of load is on your electrical system. It meters any current draw through the fusebox. (so, if you have ABS, amplifiers, etc etc this is NOT metered)

ALTC: this is an output on the ecu that tells the alternator to relax, like at idle. for some reason though, if you apply a large load this output is triggered for about half a second, like for example, when you flash your high beams.

now, if the ELD sees alto of load, its supposed to keep ALTC from kikcing on. BUT if you circumvent the fusebox in any way, the ELD doesnt see that loud. hence the problems with dimming lights with bumping systems, etc etc.

My simple fix was to cut the ALTC wire on my ecu (pin A16 obd1, B5 obd0). Now my alternator works like normal (governed by its internal voltage regulator) and my voltage is much more stable. its very obvious with my larger fuel injectors when there is a voltage fluctuation, as my AFRs change, as well as my voltage gauge, causing a funky idle.

Also, one more point, to those of you looking into upgrading your alternator to a high output unit, make sure you ask to see a graph of output vs RPM. youll be surprised to see that most of the high output alternators actually have less current capabaility at low rpm then a stock one! they need to be revved up to acheive their full capcabilities.

anyway, hope this was informative, just wanted to put it out there.

-M@