Biggiesacks

You said the serp belt tensioner started bouncing? I'm just hypothesizing that its from the alternator having to work pretty hard to power your stuff. Maybe too hard because of elecrical issues. Loaded up as in it is having to produce alot of current so it becomes harder for the engine to spin it. Or maybe its just from the engine sputtering.

nor11384

iTrader: (1)

Well, the pulley was bouncing back and forth. This happens when the fans kick on and rpms drop. I was thinking maybe this caused the voltage drop but looking at it closely it bounces and moves forward slightly as in putting more tension on the belt. Idk if it’s normal or not. Any idea how I can post a video so you can see the voltage?

Biggiesacks

That's just the tensioner doing its job. What I usually do is upload to youtube then post a link.

nor11384

iTrader: (1)

Keep an eye when voltage drops. That’s the fan turning on.

Here I have the head lights on. I’m using map tracer. Check out what the voltage does when fans turn on.

Biggiesacks

Those volts are too low even before you turn anything on. What are volts at the alternator?

Biggiesacks

Basically the alternator is trying to be above 14 volts all the time. So either the alternator is bad and not providing the power it should, or there is resistance in the circuit causing the voltage drop.

nor11384

iTrader: (1)

Idk how I would take voltage at the alternator. It is in a very bad spot and hard to get to. What do you recommend?

Biggiesacks

If your arm wont make it through, remove the strut tower bar to gain extra space. A hint, if you remove all the nuts /bolts holding it on and jack the front of the car up the struts will lower and make it really easy to get off.

Here is the factory procedure for measuring line voltage drop. If you want to use an Ammeter you would put that on the line at the alternator but the negative of your DMM at the positive battery terminal in the trunk.

nor11384

iTrader: (1)

Damn with the battery in the trunk and alt all the way down there this crap seems damn near impossible. I hate electrical gremlins. I’ve done pretty much everything on this thing but when it comes to electricity I’m not the greatest.

nor11384

iTrader: (1)

At wot I’m getting readings of 13.4 - 13.5v. That seems kind of low?

Biggiesacks

You want strong volts at WOT. Like i was saying Volts effect everything important, probably most critically the fuel injectors, the fuel pump and the ignition system.


TBH anything below 14 volts at any time is a problem to me. Except for starting and when the alternator isn't working. If it dips below 14 volts for a second but then engine speed comes up and it goes back above then thats ok too.

For a little extra context electronics are effected by the climate. Whats normal to me here in California might not be true for someone in Saudi Arabia, or Greenland etc.. Based on the information you provided though I think your case is still outside of what I would consider an acceptable range even under some pretty harsh conditions. I think the service manual agrees with me here too.

Biggiesacks

So probably the easiest pass fail kind of thing you can do is get volts at the alternator from positive lug to alternator case. If that reading is higher then the one at the battery (like more then the .3 volts the FSM called for), especially under load then its your wiring. If that number is really low with the rest of the system then its the alternator.

nor11384

iTrader: (1)

Ok I’ll try to get reading at alternator and see. Would relocating battery to the back cause a voltage drop since it’s a longer travel for voltage?

KingTal0n

First, some cars have a programmed setting which reduces the voltage at WOT to alleviate the stress on the belt/alternator
I notice in the map you are showing is something like that?

Next, if the alternator starts out bristling with voltage when cold,
and gradually seems to worsen as it heats up and more accessories turn on,
and you lose 1-2 volts from turning on headlights, fans, etc...

Then its probably just a weak alternator.
Most cars come with just barely enough alt to run the accessories they come with.
If you've added anything (better fans for example) or done anything to incure a voltage drop (battery relocation for example) then now you need an upgraded alternator or is never going to handle/hold max volts with all the electronics turned on. It probably didn't do so well to begin with.

Biggiesacks

If the cabling or grounding is inadequate sure. Distance effects low voltage DC a lot. That reading would only be at the battery though. The Ecu should still be seeing the alternator 14+ volts.