headlight on, idle revs goes down? updated 16/11/2009!

[altong0840]

I just check the voltage by the mech shop and it shows that


P gear(0 rpm), no elec load, battery 12.5V
P gear(1400rpm), only start the car, no other elec load, battery 14.0V
P gear(1200-1300rpm) , start the car and and headlight, no other elec load, battery 13.8V


so is it mean the alternator worn? cheez

[MRGRIM]

those voltages at your ALT are spot on ...
batt with car off cvaan drop as low as 11v this is normal
at charge after start it can be between 13.2 and 14.8
these are the voltages that your after for a healthy ALT.
BUT THIS DOES IN NO WAY MEAN ITS CHARGING WITH GOOD CURRENT.
VOLTAGE IS ONLY HALF THE STORY AN ALT MUST PUT OUT GOOD CURRENT

if your not having starting probs and if when the car is at idle and you put on the head lights and they dont get much brighter when u up the revs this is good as your ALT is doing its job..

regarding your idle ..
from what you said its an AUTO so in Park your rev's will be higher than in drive as there is no load on the motor at "idle"
1400 in Park is correct 900 +/-50 rpm in Drive is also correct
if the idle is droppng as low as 700 this would be the motor is cold also it should have an auto choke thermaticaly controlled these some times get blocked or corroded ..easy fix just clean or replace
another main reason for a drop can be timing, fuel mixture,can also be caused by a vacum leak from inlet to dizzy as there is no vacum to advance the dizzy due to load and being cold the rev's will drop.

a good tune and diagnostic look at it will find all these problem's and can be fixed easly...without any major exspence

Cheers
Grim

[~Sp33~]

Corroded ground wires can cause excessive load on the alternator too.

[altong0840]

Corroded ground wires can cause excessive load on the alternator too.

bingo! it help the idle not drop so much as before!!! cheez

but still the long way to go~thx~champ!

[altong0840]

those voltages at your ALT are spot on ...
batt with car off cvaan drop as low as 11v this is normal
at charge after start it can be between 13.2 and 14.8
these are the voltages that your after for a healthy ALT.
BUT THIS DOES IN NO WAY MEAN ITS CHARGING WITH GOOD CURRENT.
VOLTAGE IS ONLY HALF THE STORY AN ALT MUST PUT OUT GOOD CURRENT

if your not having starting probs and if when the car is at idle and you put on the head lights and they dont get much brighter when u up the revs this is good as your ALT is doing its job..

regarding your idle ..
from what you said its an AUTO so in Park your rev's will be higher than in drive as there is no load on the motor at "idle"
1400 in Park is correct 900 +/-50 rpm in Drive is also correct
if the idle is droppng as low as 700 this would be the motor is cold also it should have an auto choke thermaticaly controlled these some times get blocked or corroded ..easy fix just clean or replace
another main reason for a drop can be timing, fuel mixture,can also be caused by a vacum leak from inlet to dizzy as there is no vacum to advance the dizzy due to load and being cold the rev's will drop.

a good tune and diagnostic look at it will find all these problem's and can be fixed easly...without any major exspence

Cheers
Grim

thz for the information!!!

follow your method, i test the ALT and it is fine~

but i read the manual that mention the idle RPM should only be about 1100rpm, when put in D gear it should be about 900 rpm.

anyway, how can i check is my auto choke working or not?

where is the auto choke located??

cheez!

[~Sp33~]

bingo! it help the idle not drop so much as before!!! cheez

but still the long way to go~thx~champ!

No probs, make sure you check all of them, not just the negative terminal on the battery.

[MRGRIM]

thz for the information!!!

follow your method, i test the ALT and it is fine~

but i read the manual that mention the idle RPM should only be about 1100rpm, when put in D gear it should be about 900 rpm.

anyway, how can i check is my auto choke working or not?

where is the auto choke located??

cheez!

i would like to help you..
i need a little more info re the car then ill look into it further for you
also when was it last serviced ?

[altong0840]

i would like to help you..
i need a little more info re the car then ill look into it further for you
also when was it last serviced ?

my car is 93 civic EG4 Twin carb D15B4 hatchback auto
done all the fuild and belts 3-4 months ago

[MRGRIM]

my car is 93 civic EG4 Twin carb D15B4 hatchback auto
done all the fuild and belts 3-4 months ago

?? was this done buy you or mech
did u replace the dizzy cap and rotor button?
reset timming ??
adjust valve clearance ??

[altong0840]

?? was this done buy you or mech
did u replace the dizzy cap and rotor button?
reset timming ??
adjust valve clearance ??

i actually replaced the long motor+Gearbox by porfessional~ so it had done water pump, belts, fuilds, tune up timing, air/fuel mixture~ but the carby set still the old one

it just recently replace the spark plug and Spark plug lead by myself, also the gound wire kit

[sultanaz]

hey ive got a problem with my new installed mongoose alarm, i got HIDS light with the car with i bought it, its a 1999 prelude vtir. I was driving 2 days ago with my HID lights on and forsome reason i dont think they are wired correctly, it looks bodgey but they work fine, i wna fix them tho. My problem is i was driving and the immobliser kicked in while i was driving me forcing me to stop and unlock the car and start it again. this only happened once, ive had the alarm for 1 week so far. i took it back and they had a look saying it was a voltage drop, I then discovered every time i turn my HID lights on my alarm box has a TICK noise ? i can hear my engine sound drop a little too, could my HIDS not being wired up properly have set a voltage drop which is my cause ? ive taken it to a electrician and they say if the battery and the alternator is reading fine then it could be the HIDS... Im just thinking could this be my cause ? possibly wired wrong ?

please help, in desperate need. its so frustrating.

thanks.

[~Sp33~]

Sounds like it needs a better ground.