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Old 04-21-2008, 09:02 PM
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subzali subzali is offline
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Default Another ammeter question

After installing my ham, it turned off one day while I was driving, and I remembered from reading the manual that it will do that if there's more than 15V being supplied. So I turned it back on and it was showing 16V!

I don't know how long it's been like this, maybe since I had my alternator rebuilt last year? Or maybe since I put a new voltage regulator in 2 years ago! I don't know, my battery seems to be okay, and yes after holding it at high revs it would keep climbing up and peaked around 16.1V.

So last night I turned down the voltage regulator so it's around 12.2V with the engine running, and it's funny it doesn't climb at all when I rev it, so I think I might have it too low, but wanted to see how it goes.

I also noticed though that my ammeter spends a lot more time on the drain side of things than the charge. So I'm wondering what you 40 guys experience - where is it near 0? At idle? At highway rpms? With headlights on? With brake lights on? With headlights, brakes and turn signals on (at a stoplight at night) I'm almost -30A according to the gauge. Just wondering where it's supposed to sit, I think it's supposed to charge around 13.8V or so, so I'll probably crank it up gradually, as long as it doesn't take off on me and head north of 15V again...

I did see Zepp this afternoon though! That was cool since chances are low that I would be driving my 40 during the week We did a little - got one from a guy in a 60 today too, so I'm all happy
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  #2  
Old 04-21-2008, 09:23 PM
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It doesn't climb because that is battery voltage! Set the reg for 13.5-14. Anything over 14.4 is overcharging and 13 or under is to close to battery voltage.
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Old 04-23-2008, 02:44 PM
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Quote:
Originally Posted by subzali View Post
I don't know how long it's been like this, maybe since I had my alternator rebuilt last year? Or maybe since I put a new voltage regulator in 2 years ago! I don't know, my battery seems to be okay, and yes after holding it at high revs it would keep climbing up and peaked around 16.1V.

So last night I turned down the voltage regulator so it's around 12.2V with the engine running, and it's funny it doesn't climb at all when I rev it, so I think I might have it too low, but wanted to see how it goes.

I also noticed though that my ammeter spends a lot more time on the drain side of things than the charge. So I'm wondering what you 40 guys experience - where is it near 0? At idle? At highway rpms? With headlights on? With brake lights on? With headlights, brakes and turn signals on (at a stoplight at night) I'm almost -30A according to the gauge. Just wondering where it's supposed to sit, I think it's supposed to charge around 13.8V or so, so I'll probably crank it up gradually, as long as it doesn't take off on me and head north of 15V again...

I did see Zepp this afternoon though! That was cool since chances are low that I would be driving my 40 during the week We did a little - got one from a guy in a 60 today too, so I'm all happy
Your meter will show drain because the battery is supplying more power than the alternator. It will do that for a while, until the battery is mostly drained because you set the regulator too low.

While you were right, 15-16 is WAY too high, 12.2 is too low. You want 13.8 to 14.2. Ideally you will be on the low end at idle (with no other loads than the ignition to keep the engine running) and at the high end of that range at 1000 and above RPMs. You should not see any significant difference above 1000 RPMs to redline. When the engine is off, a fully charged battery should be around 12.5 volts.

Zero on the amp meter is - zero amps. Nothing going into or out of the battery. If you see this when the engine is off, that means nothing is drawing power from the battery (turning lights on for example will deflect the meter to the negative side showing discharge). If no deflection (zero amps) while engine is running, it is good! It means the system is in equilibrium - the alternator is supplying all the power to the loads and the battery doesn't need a charge. When running, if it deflects to the left, it means the alternator isn't keeping up with the loads and the battery is helping. To the right means the battery is accepting a charge.

One symptom of a voltage regulator about to fail is the amp meter starts jumping around and doesn't want to sit still. You can't see that with a voltmeter!
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Old 10-05-2008, 09:26 AM
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Okay so this is the problem I was alluding to at the meeting last week. Here's where I'm at now:

-My battery has died several times and driving doesn't seem to help recharge it.
-My ammeter will follow my engine rpm (more charge at higher rpm).
-Even with engine running, system will not compensate for extra loads (headlights for example), so if there are a lot of loads the ammeter will be on the drain side, especially at idle but even at highway rpm it will be slightly on drain side, so I feel like I have to modulate the headlights if possible (only run them when I need to) to keep the battery from draining. I'm wondering if maybe my alternator is shot.
-With no load at elevated rpm (800-1000) my alternator post is just above 13V, battery post voltage is in the 12s.
-With headlights on at same rpm, alt. post is 9.5V or so, battery is the same.

I checked some of the wiring and connections and everything seems to be okay, I'm going to throw on another alternator I have and see what happens.
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Old 10-05-2008, 10:13 AM
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I'd slip set of brushes in the alt. if the bearing are quiet. Could be the low $ fix.
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Old 10-05-2008, 10:28 AM
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have your battery load tested. my pig was doing the same thing...turned out one cell was toast.
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Old 10-05-2008, 12:00 PM
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Well I had them tested and both battery and alternator are shot. I got a new battery and threw it on. I swapped the other alternator I have and started up the truck.

battery voltage: 12.2V
alternator post dc voltage (FWIW, since it's not internally regulated I'm not sure this means much): 12.2V
alternator post ac voltage: 26.2V

I was thinking, well, if the alternator is putting out 26.2 ac volts, maybe it's alright and I just need to adjust the voltage regulator up a little bit (it's a new one from Toyota, hasn't had any adjustment yet).

But - the ammeter still drops down when I turn on the headlights (truck is running) - so the system is still not compensating somehow for extra loads. To me that's a problem that I need to figure out, but I don't know how that's controlled. Is it all through the voltage regulator? Maybe that's toast.
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1977 FJ40 2F "Brahma" + Lockright, tach, Warn 8274, FJ60 Power Steering, soon to lose the Sanden OBA to go back to factory emissions
1996 FZJ80 1FZ-FE factory lockers + Safari Turbo , CDL switch, cup holder, AATLAS1X leather, heated seats and JDM switches
2000 Tundra Limited TRD 2UZ-FE SOLD
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Old 10-05-2008, 07:15 PM
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Okay this makes sense, I think.

My alternator appears to have been on the fritz. The other alt. I put on didn't change anything really, and I had it tested as well and it too was toast. The reason the ammeter was being weird is because the alternator was putting out enough juice so that at high rpm the battery was getting charged, because all other times it was draining, so that's why the ammeter needle was changing so much depending on the loading conditions. But the alt. was not putting enough out to account for other parts of the system, like headlights and brake lights, so that's why it would drop down.

I don't know why I was getting either 12 or 17V at the battery though and couldn't get it to be happy, but if the alt. was going south then a whole myriad of problems could have resulted.

All this is theory at this point based on the fact that I had two bad alternators and one dead battery because of it; I got a new battery and I'm going to get a new alternator and put it in and see what happens. I'm just glad this lasted me through Cruise Moab, even if just barely. And the Ghost Town Run.

The part that threw me off was that I had this alternator rebuilt in April of '07, so I'm surprised it only lasted a year. I'm gonna have to make a phone call...
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1977 FJ40 2F "Brahma" + Lockright, tach, Warn 8274, FJ60 Power Steering, soon to lose the Sanden OBA to go back to factory emissions
1996 FZJ80 1FZ-FE factory lockers + Safari Turbo , CDL switch, cup holder, AATLAS1X leather, heated seats and JDM switches
2000 Tundra Limited TRD 2UZ-FE SOLD
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  #9  
Old 10-05-2008, 07:41 PM
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i've got two alternators that you're welcome to.
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Old 10-05-2008, 10:04 PM
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Matt, since new regulators are not available, I know your "new" regulator is reman. Your symptoms strongly suggest that either your "new" reman regulator is not functioning correctly or you have a wiring issue between the the alternator and the regulator (what I mentioned at the meeting).
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