Fog lights dimming

[jnorion]

I hope this is the right section to post this question in...

I just recently installed some foglights. The power wire runs directly from the battery, through a relay, and then grounds into the frame. When I have the foglights turned on, they go dim and the heater fan slows down while I'm idling. When I rev the engine up above 1000rpms or so, they turn on full power again. If I turn the fog lights off, everything runs normally.

Is the problem with my wiring, or the battery, or the alternator, or what? Is there an easy way to fix it?

[blue LEDz]

it's quite possible that at idle the alternator is not capable of supplying enough current to everything, like the fan and lights. can you check the voltage? when you tested it, do you have your headlights on? but it's probably just the crappy 2 part voltage regulator of the stock alternator

[jnorion]

I don't have any way to check the voltage on it. When I tested it, the headlights and fan were on. Turning the fan off made a difference, but they still dimmed a bit. Turning the headlights off made no difference.

A friend of mine also said the problem might be that I'm running power straight off the battery. Something about drawing too much for the system... but I don't see why it would make a difference where the power comes from if it's too much for the system to handle.

[blue LEDz]

running it straight off the battery will not cause a problem. it sounds like it's just the crappy charging system with the engine running, headlights on, and fan going you are probably using 75-80% of what the alt can put out at a higher RPM. at idle the alt can't put out full power, which is why when you rev it over 1k rpms everything is fine. adding the fog lights, at idle the alt just can't keep up, and if you left it on idle with all the lights on and fans running, the voltage would probably continue to drop, till the car possibly shuts off, but that could take hours. basically you are utilizing all the power the alt can put out at idle, and then some, which comes from the battery, so it's at a lower voltage. as long as it stays above 12.5 volts it's ok, though

[jnorion]

So basically for short amounts of time it's no problem? Or should I not use them unless I absolutely have to, so I don't drain the battery? I've been using them as running lights during the day instead of my headlights, but maybe that's not such a good idea.

[blue LEDz]

So basically for short amounts of time it's no problem? Or should I not use them unless I absolutely have to, so I don't drain the battery? I've been using them as running lights during the day instead of my headlights, but maybe that's not such a good idea.

trust me, if i can crank my system at idle for long periods of time, the fog lights won't do any damage run them all you want, in order for it to do any damage you would probably have to leave all your electrical components on, including the fan, headlights, and fog lights for 10+ hours at idle.

[Boston]

The alternator doesn't put out as much current when the engine is at idle because everything is spinning slower. The charging system on the 1st gens is barely adequate, which kinda sucks if you want to add any accessories.

[Kevin]

thats kind of hard to believe that an 03 protege would have such a problem with running fogs.. what kind of bulbs do the foglights use? at any rate, foglights really aren't useful if conditions warrant the need for low level lighting ...so in other words, don't use them as driving lights unless you're in pitch black area's. aside from that, truthfully, "rent" a volt meter from radioshack or your local automotive parts store for a couple bucks and check your voltages.. where, bryan or daryl could tell you.. but reguardless.. spend the 20 to 30 bucks, and return the thing when you're done with it.
peace

[jnorion]

They use H3 bulbs, standard halogen. I wanted to use them as running lights during the day just because I like how the lights look lower to the ground... they have no practical value unless it's actually foggy. At night when I actually need to light the road I really couldn't care less whether I have four lights running or only two... I just want to see the road. At this point I think I'm just going to save them for bad weather and just use the headlights as I did before.

[dacinokc]

The protege has a pretty low output alternator. Headlights and blower motors can eat up just about all of it's output at idle.
Most all alternators have very low output at idle. It really makes sense if you think about it, the car is meant to be moving, not sitting at an idle, if one hops up the idle output, it would be producing way too much current at driving speeds. That might sound good, but too much is not good either!
The higher the output of an alternator, the more torque it takes to make the shaft turn over. For low rpm output you would need a lot of wraps, so a tremendous torque on the engine. The more torque required, the less horsepower for other things like getting up and moving! In turn, it is much hardware on the engine to be "pulling" something that requires that much torque.
Even if you overcome those issues, output is in a curve, if you move the output curve to the right to get more output at really low RPM, then you would find output at driving RPM to be sizzling! You would either boil your battery to death with too many amps, or you would need a power regulator the size of Godzilla to regulate the amount of power.
In competition audio, classes allow for specifc RPM during runs, mostly below 3500 RPM. In the hot dog classes like Burp cars, folks don't ever bother with idleing the motor, it couldn't keep up with the drain if it had to.
I probably went into too much detail, but the bottom line would be at idle, a protege will dim on fog lamps or blower motors, or a bunch of amps. It would be if the car is dimming when you are at 2500 RPM I would be looking for charging system problems.