Headlights lower idle

[iBoostDSM]

Something weird just started happening with my car. When I idle without my lights on its steady around 1000rpms, but when I put my headlights on it drops a bit to the point where it almost dies. I don't no what's going on...please help.

 

[BoostedinSoFla]

Sounds like a dying alternator...

 

[bradselph]

i also agree

do the lights get bright when you idle it up and then dim when you let off

id take it off get it tested and most likly replace it soon before you get somewere and you cant start your car

 

[iBoostDSM]

i did have my alternator tested a few months ago and it was fine. Hopefully it wasn't fine then and is now dying. I dont know about them getting brighter when i idle up, I was going to test that tonight.

 

[4g63monstr]

do a voltage test by placing the leads across your battery terminals. at idle with everything possible that you can turn on in your car your battery should be receiving between 13.7 and 14.5 volts constantly. If not, you have a problem.

 

[iBoostDSM]

i also agree

do the lights get bright when you idle it up and then dim when you let off

id take it off get it tested and most likly replace it soon before you get somewere and you cant start your car

i tested this a few minutes ago and when I idle up the lights get brighter then when I let off the gas they dim back down.

I also did a volt test. When i have everything on it reads 12.30 to 12.50, but with everything off it's at 14.00ish.

What do I do next?

 

[2GbTalonGuy]

Looks like the alternator is weak. Your next step is to call your local mitsu dealership and order a new alternator.

 

[DhampirZero]

Or you could go to your local junkyard. Alot of times their pretty cheap and some junkyards even have pretty sweet sells. One of the ones here in Indy has them on sale all month for $12. Another possibility would be the classifieds here.

 

[BoostedinSoFla]

Trust me on this one my first post got right to the point because I had the exact same problem. First step: remove the alternator and go have it tested.

 

[iBoostDSM]

That was my plan to get it tested again. Do you guys think that it could be my timing. When i got the car, which was about a year ago, i replaced the timing belt. So if you think that could be the problem I would like to check that too.

 

[66ss]

def in the charging system.....check all your connections first like battery terminals and such

 

[bradselph]

12.30 to 12.50 is pretty much running off the battery get that thing replaced

 

[jaydubb1988]

I have the same problem, I just replaced the alternator last friday due to a dead car and the battery is less then a year old could there be any thing else that could cause it? my car idles around 1k and when lights are on it drops to 600ish.

 

[cookmeup272]

Its your alternator. I wouldnt even bother getting it tested because they throw out false-positives all the time. Just go buy a new one...they usually come with lifetime warranties

 

[XLR8]

As much as I hate autozone alternators they have ones with lifetime warranties and even if you get a false positive result you can tell them the voltage it makes on the car and they will usually take care of you.

 

[iBoostDSM]

Ok, I'll get a new one asap, but is there anything else that can cause this like timing or the connections?

 

[cookmeup272]

A bad ground MIGHT do it....but its the alternator. Believe me, I have the same problem.

 

[iBoostDSM]

Ok do you think I should get an autozone one because of the lifetime warranty or just go with another OEM one?

 

[98dsmkid]

Ok do you think I should get an autozone one because of the lifetime warranty or just go with another OEM one?

i don't really trust autozone parts... if you have money to spend get an oem one but if not go with the autozone at least if ## alternator blows you can replace it ...i got an autozone one and i replaced it 6 times in the past 9 months...now i have a oem one and havn't replace it yet

 

[iBoostDSM]

i don't really trust autozone parts... if you have money to spend get an oem one but if not go with the autozone at least if ## alternator blows you can replace it ...i got an autozone one and i replaced it 6 times in the past 9 months...now i have a oem one and havn't replace it yet

Ok I'm crossing autozone off the list then. I'll just go and get an oem one. thanks for that warning.

 

[cookmeup272]

Im not wasting my money on an OEM one...Im definitely getting an autozone one

 

[tsi87889095]

I have the same problem to. I replaced my alternator about 6 months ago and still have the problem. I went with an auto zone one even know i dont like getting parts from them and luckily i got a mitsu rebuilt. How do you test for a bad ground. If you use a test light on a ground and it lights up does that mean its good? Thanks for the help and hope it helps others.

 

[steve]

While he may have an alternator problem he clearly has an ISC/IAC problem. Could be the stepper, IPS, or ECU causing it but the idle speed shouldn't drop like that and the idle should be at 750+- 50 RPM without DSMLink or a custom EPROM.

 

[iBoostDSM]

I've replaced my ISC multiple times, but I dont know if I ever found one that works right, they were from the junkyard.

 

[steve]

If the drivers in the ECU were damaged to start with you could put a brand new on on and it wouldn't fix the problem. When I talk about an ISC problem I mean the whole idle speed system, starting at the ISC (inside the TPS on a 2G and how you set the TPS), the ECU, the BISS and the stepper motor in the throttle body. Each has to be functioning, and clean for the system to work.

When they are functioning the idle speed will be 750 RPM when the car is warmed up, don't drop when you turn on the heaglights, put a load on the power steering, or turn on the AC. The only way to make a factory ECU idle higher is to drive the ISC out of range where it's all the way closed and then continue to increase the bypass air using the BISS or due to a leak.

There is a youtube video on how a working ISC behaves during initial power up of the ECU when it recalibrates. If yours doesn't then it's time to track down why.