acousticrawk

so heres a video of my 4runner... the voltage drops and jumps back up when my lights are on. even if its just the running lights on it does this. at idle when the voltage drops, it causes my idle to drop to 500-600 RPMS sometimes a touch less. when the voltage drops, it def draws power from the engine. when none of my lights are on, this doesnt happen. other electrical devices have no effect (ie- the blower running doesnt cause an issues, i dont have a radio.. so i dont know if that would do anything)

ass you can see at the 25 and 40 second marks, its a pretty abrupt drop and quick climb.

thoughts on what is causing this??

[YOUTUBE]http://www.youtube.com/watch?v=9zdh4_nuE9Q[/YOUTUBE]

justin_4runner

could be a ground for the lights or relay. also check the connections at the alt to make sure there tight and your post on the battery,

corax

Mine does this also, I can watch the needle jump up and down with the turn signals or any other load. I don't think there's much that can be done about it, the gauge reacts faster than the alternator when a load is placed on the electrical system.

acousticrawk

i get a tiny little tick on the gauge with the turn signals and when i hit the rear window button... both of which are perfectly normal. but for it to move this much at 65 mph only with the lights on? i dont think so... headlights should be a steady draw causing a steady and minor drop. there is nothing normal about this... especially because of how much strain it puts on the engine. connections are all solid and have new cables. battery and alternator wires both are larger and brand new... and again.. connections are good.

headlight relay might make sense... where is it located? sometimes my low beams turn off and if i click the brights on and off, they come right back on. and sometimes when i first click the lights on i dont have any low beams until i flight the brights on and off.

acousticrawk

corax

Maybe run start unplugging and re-plugging in every connector involved to try to get a better contact in case you're not getting full voltage where it needs to be - engine control module and alternator would be the 2 biggies. If you have a volt meter, you might want to start doing "voltage drop testing" along the power circuits from the alt->batt->fuse box and from the alternator case to batt ground (google "how to voltage drop test")

SoCal4Running

Possibly the alternator is starting to die. It almost looks like somthing is cycling "ON" but is not the case.

Can you find another alternator and swap it in and see if it does it?

On my 86 the alternator needle used to move with the turn signals, windshield wipers or brake lights. I put LED light in EVERYTHING I could and it now stays put and doesnt move anymore.

acousticrawk

im thinking its time to get a new alternator anyways... before i get a few hundred miles into my road trip and it does. is there an upgrade? from another vehicle? not looking at spending 300 bucks or something crazy
.

acousticrawk

bumpski

MrPeepers

hmm, i had a similar issue on mine where if I turned the lights on it dipped the gauge and the idle dropped, and I could make it worse by rolling the windows up, and if I held all 4 window switches up while the windows were already up all the way I could actually kill the motor. Mine ended up being that 3 piece + battery terminal, was all corroded. But you say all your stuff is new, and from the info about having to hit the brights on and off it sounds to me like maybe your actual light switch is going bad and grounding out or something.

corax

'92 or '93 Toyota MR2 TURBO - probably worth double checking the year range on that though. IIRC it's a 100 or 120 amp alternator and I think you might have to change the 3 pin plug in the back, but it's not an uncommon plug so you should be able to snip one off a harness at a junkyard

My87Runner

i know its a old thread but did you find the problem. My lights do the same thing and having the same voltage issues.