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Turning on headlights drop rpms, wth?

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Old 02-26-2011, 05:59 AM
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Turning on headlights drop rpms, wth?

'86 4Runner, 22RE, switched to halogen headlights 6ish months ago, for the past few months, when I turn on the headlights and sometimes when the headlights are on and I turn on the turn signal my RPMs drop and feels like my engine is going to die. No real idea whats going on here. Maybe the halogens are taxing the headlight relay? If it is a relay issue, do I just need a new one, or an upgraded one? If I need an upgraded one...any suggestions?
Old 02-26-2011, 06:03 AM
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mine does the same with hids. im planning on upgrading my alt. that should fix the problem. im also running alot of accesorys
Old 02-26-2011, 06:07 AM
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mine does this too, but not nearly as bad since I made my own wiring harness for the headlights. : http://www.4crawler.com/4x4/CheapTri...adlights.shtml
Old 02-26-2011, 06:16 AM
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Yea it's the alternator dragging down the motor. My 86 4runner did the same thing until I switched every light except the headlights to L.E.D.'s.
Old 02-26-2011, 06:21 AM
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ok good to know, what alt. is a good upgrade?
Old 02-26-2011, 06:23 AM
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I would start with cleaning all your grounds, battery cable and connections to/from the alt. Your gonna have to do it anyway with a higher amp alternator. Upgrading your battery cable to a higher gauge will help as well. The larger the gauge of wire the lower the voltage drop across them. The lower the voltage drop the lower amount of current that has to be supplied. = less strain on the alt.

I think this is why the headlight harness upgrade affected how much my alt affects the alt thus the draw on the engine and idle change.

FYI when I turn my heater on my idle drops from 950 to a little under 800.

Last edited by xxxtreme22r; 02-26-2011 at 06:27 AM.
Old 02-26-2011, 06:31 AM
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Originally Posted by Heyworth
ok good to know, what alt. is a good upgrade?
im planning on running trail-gears GM to toyota conversion. the bracket cost about 40 bucks + shipping and then the cost of a GM alt. well worth it. Im running an amp,lights,onboard air, a winch, hids, as well as the selenoids for my horns off my batt. so i need all the charging power i can get.
Old 02-26-2011, 06:48 AM
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Awesome guys thanks a ton
Old 02-26-2011, 08:48 AM
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The GM alt swap is a good altrnative to the expensive higher amp aftermarkets.

I have a few in the garage and even made the bracket but still haven't put it in.
Old 04-11-2011, 07:38 PM
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so I've been looking at this and I can't see the advantage yet. most of the GM alternators I find that should be compatible with the adapter kit are around the stock 70 amps and $70-$100 ( the only high-amp GM one I saw was about $120. plus $40 for the adapter kit.

aftermarket toyota alternators that do 130 amps are going for $140 or less. am I missing something?
Old 04-13-2011, 04:44 PM
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You can upgrade the armature of the alternator to a higher amperage. There was a write up on it on 4x4wire.com. You can also take your alternator to a shop and they will convert it for you.
Old 04-13-2011, 05:49 PM
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I don't doubt that, but you can still get cheap high output stock alternators. why do all that work if it's not saving you money?
Old 03-30-2012, 10:03 AM
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guess ill start this up again, having the same prob. my voltage doesnt change with the lights on, but does drop 1-200 rpm, voltage stays right at 13.8 v. does anyone know WHY the idle even would drop, i cant imagine the coil cant keep up even if the alt drops voltage a bit...
Old 03-30-2012, 10:51 AM
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Do your headlights get brighter when you rev the engine?
Old 03-30-2012, 10:59 AM
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no they dont dim either. its always done it, kind of figured its a toyota thing. seems dumb though. i think 22re's have a finicky idle issues in general.
main prob with mine is ONLY when it rains it wants to die when coming to a stop, (i cut the wire from the brake to the ecu so its not that)
Old 03-30-2012, 01:27 PM
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The voltage stays the same because the alternator is maintaining it within a certain range. The reason that the engine slows down is because the generator is working harder and drawing the work from the fan belt.
The field windings are being sent more current which creates a stronger magnetic field that the armature must pass through creating more electricity for the battery and electrical system. The stronger magnetic field is harder for the armature to pass through creating more drag on the belt pulley. That drag is what pulls down the RPM's.
Old 03-30-2012, 01:52 PM
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ok so its simply a drag on the engine, that makes sense. so would a heavy duty alt always put a slightly higher drag, but not be as affected by a load such as a headlight while idling?

sounds like the poor little 22r doesnt have enough torque at idle to keep up with the electronics we tend to put on it (does, but not perfectly)
Old 03-30-2012, 01:54 PM
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by the way, i cant believe i didnt think of that. thanks buck
Old 03-30-2012, 02:14 PM
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so who wants to buy my new Trail-Gear GM alt bracket for $35 plus shipping
Old 03-30-2012, 02:16 PM
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Yes, likely the drag of the added load on the alternator. After all, the A/C compressor and power steering pump are both fitted with "idle up" features to boost idle speed when either of those devices are on at idle. You could probably wire up some relays to pick up that the head lights are on and have that bump up the idle via the A/C idle up VSV.

I essentially do that on my '85. A/C is not hooked up but I left the dash switch and the idle-up VSV. When wheeling, especially at higher elevations at night, I'll just flip on the "A/C" which turns on the VSV and bumps the idle speed up.


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