i tried to reply here (https://honda-tech.com/zerothread?id=838099) but it wouldnt let me for some reason. but I am having the exact same problem. also it is a 97 dx with ls swap obd2a all stock. I just replaced battery and alternator with no luck . anyway did anyone ever figure this out? and what two wires or wire do you disconnect / jump at the ecu? or what tells the alternator when to start charging?

Thanks for help. this is really driving me crazy! lol

 

if the system, electrical system, is under a high load - the lights will do that.

Stock 95 Civic DX..

Blower > 3 Lights dim,
If i turn off my fogs, i get some brightness back...

It is the amount of power that you are drawing, if you really want to fix this - try upgrading the "big 3" - basically main three battery wires, Ground, Power Dist, Alternator...

 

yea but this is different. its like the alternator is charging at all until the rmps get above 3500 and then as soon as they go below it stops charging again. Does anyone know if the ALTC wire going to the ecu does. Ive heard you can cut it if your voltage is fluxuating. Guess I'll try tomorrow and see what happens

 

if i'm not mistaken, it just "detects" electrical system load - it is supposed to change the idle speed...

ever notice that your engine idles a little higher when your lights/ac on?

if you cut it the ecu might just default to "full-load" mode and bumps up your idle speed. <-I'm not to sure about that, but from what you said it does that is what i think it does.

You could check that fuse in the main fuse block - i think its the voltage regulator fuse or something... i dunno exactly - all i know is that fuse is connected to a device that tells the ecu what the current system draw is... that device could be malfunctioning - but i seriously don't know.


What bulbs are you running? Do you have fogs? High Power Stereo?

 

well pulled the ALTC pin out of the ecu today and problem solved! Not sure what it does but everything seems to run the same just no more dimming