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car wants to die while driving with headlights

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clipto

10+ Year Contributor
2,317
5
Oct 8, 2011
Portland, Oregon
My friends 1g has an issue when he drives at night and the headlights are on when he goes to apply the brakes the car wants to die. But only when the headlights are on. Any ideas I tried reading some threads but nothing was really a understandable answer for this. Any idea or points to where and what might causing this? Tested the battery and it came back strong. Should still check the alternator? Or if anything I read is a bad ground but I am no electrician as I have no idea anything about the wiring for this car or any car beyond basic install of a stereo LOL. I do see on the log that the battery volt does drop when applying the brakes down to 12v when fully braking to a stop from a steady 14v at cruising/idle. Or maybe its the dinky small ground wire that goes from the negative on the battery to the back firewall.
 
Bad or too small of a ground is what immediately came to mind when I saw this. It should have a ground from negative post to firewall, negative post to bell housing, and intake manifold to firewall. Check to verify if these are still there, and if so, if they're in good condition, I.e. not burnt
 
Yes the trans bell housing has the original ground as in good condition so is the one for the intake manifold. But the one on the firewall on the negative post on the battery is a dinky small one. But I could sworn that earlier within this month the car was running fine with the same small ground wire on the firewall to the negative post and not having any issues. But none the less I will get to replacing it asap with a bigger wire and make sure its got good contact. Still taking input tho what else to check.
 
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I would change the grounds any way. I have had a couple problems that came out to be bad grounds. Most recent was my car was running at 225 and almost overheating, found 2 grounds that broke fixed them and now running good. I would also do a draw test in the alt and make sure it's not shot. When I first got my car the alt was bad, and it would die randomly, and work randomly.

Good luck though hope you get it good.
 
If you find out the alternator isn't up to snuff, do a favor and replace it with a 96 Galant unit. It is a higher amp unit and a direct bolt on with 90 amps. A local parts store should be able to test yours. Under a heavy load you might be pulling enough amps that the fuel injectors have a hard time firing and fuel pump supplying enough fuel. It fixed my 1g. The stock unit is a 65 amp I believe so with lights on fuel pump running radio on and such the addition of the draw of brake lights on the circuit my just be sucking the last few amps of the alternators max output. 12 volts is kinda low to keep everything running correctly. Try loading the car with every accessory possible and see if it does the same thing. Its a poor man's way of load testing your alternator but I would bet it makes the car die also. Run the radiator fans, a/c and fan on high, all lights...anything that can draw on the alternator then post back.
 
Check the alternator belt tension, it could be slipping. Run a ground from the alternator case to the chassis on the driver side. Upgrade the positive wire from the alternator to the battery. I run a 4 gauge.

Auto or manual? What rpm does it idle at?
 
Agree on weak battery. I would think the alternator would try to compensate. Very good simple suggestion. Sometimes I think it takes more juice to run these things than to start them. Yes having rhe battery tested is a easy way to check that off the list. The load test I described would not tell if it was a bad battery or bad alternator but would be simple to see if it died like before.
 
Car is a 5 speed idle is 1000rpm and the battery is good. Was tested and is rated at 550 but is pushing 570 so its a good battery. The battery shows 14v all the time when the car is idling with the headlights on too its just once u apply the brakes just enough that the rear brake lights come on with headlights it starts to drain then it really drains if u have to apply a full brake to stop. But it doesn't do it with just like the side markers on on and no front headlights.
 
Does he have ECMLink or a way to see the ISC data? Mine acts like that when my ISC is way too high...like 90. It doesn't have enough to compensate with the increased load and coming to a stop and the rpms drop real low and the lights dim and it starts to stumble. Only at night with the headlights on.
 
^I thought I that too, both cars had bad ISC's giving a lower idle under high battery load, but he's also getting a large voltage drop. Grounds, alternator, battery or a short in the brake lights.

I've had my car do the same, for me it was a boost leak in the brake booster line.
 
Yes there ecmlink no isc no fiav no iac or whatever none that stuff on the car tho ecmlink taking care off all that. Today we put new heavy gauge ground wire on the negative terminal to the firewall and tightened up the alternator. Symptoms seems better by will fully know tonight how it reacts. I'm starting to think its a weak alternator a low watt one.

Update: Ok so i put a new ground on straight off another 1g so its the stock thick one that goes to the firewall and i was having issues with the tensioner for the alternator but its decently tight And the alternator fuse is gold, but on a side note I got to drive it tonight with the headlights. Now when i tap the brakes just enough for the brake lights to come on without the headlights on its fine. But when I turn headlight switch just 1 click to where the sidemarkers are on it drains a little more battery and rpms drop when barley hit the brakes just enough for the rear brake lights to come on, and finally when the main headlights are on and i barley tap the brakes just to turn on the rear lights it sucks down super hard. So as I assume I think its time to go throw on a new alternator get the belt down good on it and see if his problem goes away,also will check with the tuner about this and check the rear brake lights for a shortage somewhere. Last but not least will eventually will be checking the brake booster but like i said there is no pressure vacuum when barley hitting the brake pedal to turn on the rear brake lights with the pedal. So i am big assuming its probably the alternator and will see if I can get this car some more juice to run off of.
 
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Don't think it's a bad ALT since you're showing 14VDC at the battery at idle.

BUT, does your dashlights flicker, or dim or any other device dims then brightens up?

If so, then the ALT is definitely toast since the "com" brushes are shot and a rebuild is in store or a reman..but not from AZ, but a respectable ALT/Starter shop.
 
I would be checking the current in the power wires and making sure the ground is solid and not shorting before you get a new atl. Last year I didnt check anything and just threw on a alt and it was my fuse LOL. I know you checked the fuse. Check the wire in the bottom of tge fuse holder where you unscrew the fuse make sure it has good connectuon and the power wires to the alt. Make sure theres no breaks or anything.
 
Ok I hear you but the bolt holes are kinda stripped due to someone using the wrong bolts threads in em so the tension on the belt is not the greatest. But yes I will check over the all the wires the best I can.
 
tension on the belt is not the greatest.

BINGO ! A good answer. Belt has to be tight enough to have a quarter inch deflection when you press the belt in the middle between the two pulleys.

Otherwise, the battery is being taxed to death from not getting a full charge from the alternator to keep it charged.
 
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