Wiring holding residual charge?

[DomSmith]

I've been trying to sort out some electrical issues on a 65 FJ45 (sat for 10 years but I have driven it 2K miles since) and am finding some very strange stuff. It all started when I tried to add an amp: https://forum.ih8mud.com/40-55-series-tech/265529-amp-question-65-a.html


History:
There are quite a few things going on so bear with me. First of all the voltage regulator was allowing 16+ volts to the battery so I've ordered a new one. In the meantime I'm using a spare out of a 73 and it's limiting the volts as it should. I also tested the alternator and it was only charging at 5 amps so it's being rebuilt. Has a brand new OEM fuse block, good grounds at the starter and battery (I just pulled it all apart again today and they're as good as it could ever be). I currently have a donor alternator in the rig that is not hooked up (just to turn the water pump) so I can move it around as needed. All three wires are seperately covered and attached out of the way.

While troubleshooting the electrical I noticed the AMP meter was loose (not the connections but the mount). The PO had JB Welded some crap on there to hold it in place? I've since rectified the problem (I think) by using some rubber o-rings in place of the insulators that are no longer there which allows it to be tight. The amp meter has always bounced erratically since I've owned the truck but even more so now. Like "omen" style now and then when the alternator was hooked up.

I know, too many things going on. Many parts of the equation can be removed once i have the rebuilt alt and new VR in place. If I could order a new AMP gauge from Toyota I would just to be sure.

So the issue I just found that may explain much of this is...



(With the alternator unhooked) The white/blue wire that goes to the B on the alternator has 12.75volts. Disconnect the negative battery cable and the wire still has 12.75 volts. Turn the key one click to "ON" and the volts go away. Click back to the "OFF" position and the volts go slowly from 0 to .30 over a 90 second period then stops there.

HELP!

 

[vk7ybi]

Theres probably a capacitor in the regulator or somewhere else thats retaining volts. Did you put a filter cap on your amp, as discussed in the other thread?

 

[DomSmith]

Did you put a filter cap on your amp, as discussed in the other thread?

Haven't got that far yet. I want to have the new alternator and voltage regulator before I do much else. Should be done tomorrow. I'm really thinking I shouldn't need a filter cap if the electronics are all squared up, right? A $100 patch seems a bit over the top.

 

[DomSmith]

Theres probably a capacitor in the regulator or somewhere else thats retaining volts.

So maybe this is normal? And I'm Chicken Little?

 

[vk7ybi]

Yes, thats logical.. If the system voltage was going high, the drop in amp volume could be caused be a protection circuit working in the amplifier, when you turn accessories on the voltage fluctuates and causes problems.. The amplifier may, depending on design, produce more output with a higher supply voltage, so when it goes over voltage it limits volume and therefore heat dissipation in the output stage, attempting to save itself.. A faulty charging circuit is likely the cause, square that up and see how you go after that..

I wouldnt be too worried about the residual volts there, but I guess you can track it down by a process of elimination, removing fuses and unplugging unfused components till you find it disappear..

 

[Pin_Head]

None of these things are obvious problems.

The battery has a little surface grime on it that is completing the ground path with the negative cable disconnected. This only indicates that you have a sensitive volt meter.

What the amp meter is indicating depends on the charge state of the battery. If it is charged, the amp meter should indicate near zero. This doesn't mean the alternator is bad. Discharge the battery by pulling the coil high voltage wire and cranking it for 30 seconds. Then it should show a higher rate of charge.

The amp meter bounce may be due to sticky contacts in the VR. This is not a big deal, but you might want to try the new VR and adjust its output voltage as described in the FSM if it is indeed too high. Make sure that the ground wire from the alternator to the VR is good first.