Idle drops when headlight is ON

[Bagetz]

hi, Im from the Philippines, I have a festiva [Kia pride here in the phils], year 2000 Model with B3 engine [carb not EFI] manual transmission

my problem is the RPM or Idle Drops and engine will shake if i turn on the headlights, I can feel the vibration even on the steering wheels.

if headlight is off and I turn on the aircon, everything seems normal, but what I turn on the headlights the RPM goes down again to about 400-500rpm

-the battery is new [3months] and the alternator is also new [4months]

I have tried the DIY headlight wiring here:


but nothing happens, RPM will go down again everytime I turn it on...


Thanks in advance and Mabuhay!...

[SoCalZ28]

Was the DIY headlight harness installed exactly to the the instructions or was there an alternation? Also, Did the idle drop before the DYI headlight harness install? Do your lights work correctly? Are you blowing any fuses?

It sounds like the engine is struggling under headlight load. Maybe a broken wire, corrosion causing resistance, a poor ground or a common ground (don't put too many grounds on the same screw/bolt).

[Bagetz]

yes sir it was installed exactly as per the DIY diagram and instructions...
I did try the DIY headlight relay because of the idle drop problem but nothing happens.. idle drop is still there..

headlights is fine and working... no blown fuse is experienced... thank you for the inputs sir SoCalZ28

[bravekozak]

You are not the only person to have this problem. Have you googled around for an answer? Try other things, like unplugging tour dimmer switch, so your instrument lights are taken out of the equation. Disconnect one headlight to see if the problem is reduced. Reconnect that headlight and disconnect the opposite one to see if the problem is related to a specific side. Report back please. Boston choked in the final game.

[zoe60]

There is a vacuum thing at the drivers side rear of the carb. Actually mounted on the intake manifold with a linkage to the throttle. It has two vacuum hoses coming from it to two solenoids mounted on the firewall. One of those is the electrical load solenoid and one is the air cond. solenoid. The ones with the orange and brown plugs. Can't remember which is which. Check all that stuff. They are supposed to raise the idle for electrical load or air. The electrical connectors are controlled by the ECU. There should always be 12v on one side. If you remove the ground from the other terminal, the solenoid should engage and raise the idle. Air increases idle more than electric load. Hope that makes sense.

[Bagetz]

You are not the only person to have this problem. Have you googled around for an answer? Try other things, like unplugging tour dimmer switch, so your instrument lights are taken out of the equation. Disconnect one headlight to see if the problem is reduced. Reconnect that headlight and disconnect the opposite one to see if the problem is related to a specific side. Report back please. Boston choked in the final game.

yes sir but Google search always suggest to do the DIY relay which I did but problem is still there..

one more thing.. if I disconnect the wire from Alternator to the Battery for about a minute or two and then connect it again and start the engine.. the problem goes away...
but when I turn off the engine and turn it on again, the RPM drops is still there if I turn the headlights on..

There is a vacuum thing at the drivers side rear of the carb. Actually mounted on the intake manifold with a linkage to the throttle. It has two vacuum hoses coming from it to two solenoids mounted on the firewall. One of those is the electrical load solenoid and one is the air cond. solenoid. The ones with the orange and brown plugs. Can't remember which is which. Check all that stuff. They are supposed to raise the idle for electrical load or air. The electrical connectors are controlled by the ECU. There should always be 12v on one side. If you remove the ground from the other terminal, the solenoid should engage and raise the idle. Air increases idle more than electric load. Hope that makes sense.

Noted will check it sir thanks...
i'm not sure if my car has ECU

[Team Lightning]

I would look at the amp draw on the headlight circuit since that seems to be the reason its slowing the motor down. You might be able to take it to AutoZone or your local parts store, ask them to check the battery. Get them to check the amp draw with the lights off and the lights on. Also, are you running after market bulbs or the stock ones?

[Bagetz]

stock sir here in the Philippines 55/65 watts

[Bagetz]

...tried cleaning the main fusible link yesterday but no luck..
i'm thinking of making a new set of harness for the headlight but I cant find any wiring diagram as of now...

[bravekozak]

Bag, here is what you need. Section G. Delete after you finish checking for errors. "L" stands for blue.

[Bagetz]

many thanks sir ty1

..looks like there is no relay on the headlight based on the diagram..

[bravekozak]

Correct. The headlight circuit is similar to 88/89 carb Festivas. No relay. It is a very simple circuit. The red/blue stripe wire is the low beam and the red/white stripe is the high beam. Pull the 10A DIM/DIP fuse and see if the voltage drop disappears. Headlight juice flows through the red wire from the fusuble link to the combination switch. DIM/DIP juice flows through the white wire to the combination switch.

[Bagetz]

Sir pardon my ignorance but what is DIM/DIP?

[bravekozak]

If you don't have the fuse marked DIM/DIP, then don't worry about it. No resistor.

[Bagetz]

thank you sir bravekozak, I think I have a Corrosion or wire damage, even if I unplug the one headlight bulb the rpm or idle drops is still there and the voltmeter is also dropping slowly from 14v to 11.8 when the headlight is on and on idle... when the vehicle is moving the voltmeter reads 13.6 - 13.9 headlight on, if headlight off it read 14.2 - 14.4