Alright guys I'm new to this forum and I know how everyone is about saying just search this ****, but I promise you I have and to no avail.

I have a 93 civic coupe with a d16y8 block/z6 head, skunk2 cam, homemade headers full exhaust blah blah blah, recently put in a set of basic gauges because the kid i bought this from had everything screwed up i mean everything just about.

Ive got this thing to run great for the last year, but after installing the volts gauge I noticed that with everything off as far as accesories and blower the car after about a minute and a half will drop down to about 12.5v, but as soon as lets say i push defrost on and turn fan speed to 1 all of a sudden I have 14.5 and it will never drop until I turn off the defrost. The car had A/C originally but the kid before me removed it. Ultimetly it leads to my idle lowering to 450 500ish and the car started stuttering. Also noticed that when I apply the brakes it spikes my alt down 1.5v...seems a little ,much to me or am i being paranoid?

I'm a tech at a shop, I know its sad but both me and my boss are both stumped to as why it would do this, because a proper bad alt would do just the opposite when you turn lights and blower on high for a few mins as you watch it drop. My boss said its possible your battery is full charged and the ecu is telling alt dont charge the battery until there is an additional electrical load besides for the dizzy and injectors. but every honda thats came into the shop always has a min of 13.6 it seems like. this all happens like i said about a minute after everything off and car is idling. honestly my idle is a little low around 650 with defrost on, my tach is off about 300 rpms, is it possible that idling too low just disables the alt?

So ym question to everyone here is has anyone had a simliar problem? Could this be something that I fix by jumping the TEN connector and then setting my base idle, which I never did? BOTH ALT, AND BATTERY ARE BRAND NEW.

Sorry for the book above, I appriciate the help I really do and I anticiapte I'll have looked dumb as **** in some of your eyes but sometimes it helps to have a fresh set of eyes when your stumped. -
Blake

 

The ECU can command the alternator to cut the voltage to 12.5 volts, but I don't know exactly which circumstances make it do that. Generally the ECU will dump everything that it can (A/C in particular) when the idle is too low, to avoid stalling.

If you have a model with 5 brake lights (two on each side and one in the center), that array of bulbs draws almost as much current as the headlights, including a big surge when the pedal is first pressed.

 

Is CEL code 20 thrown by the ECU?

Does the charging system light (battery symbol) in the cluster turn on and stay on while the engine is running or idling?

Does the charging system light in the cluster work?

 

thank you for the responses i appriciate them. to mk378 i think you may be on to something i did not know that a lower idle would cause it to cut them out but absolutely makes perfect sense, also i do have the 5 brake lights so that would explain that so im no longer worried about the lights.

to ron j i dont have any codes at all and yes i tested the light and it comes on when alt is disconnected .

but to both of you , i found the issue to be the idle. my cluster was reading about 1000rpms at idle but infact under the timing light it was only at 550 to 600, i jacked it up to 660 to 700 and took care of my issue. i greatly appriciate the time from you guys thanks again!

blake

 

Glad you got it sorted out. Nice work.