regulator question

[TLXregnar07]

Shouldn't there be no current flow when hooking up the battery with ignition off, and the one battery power fuse pulled? I have a slight current when the cable contacts, but of doesn't happen when the regulator is unplugged. Does this suggest a bad regulator?

[71PA_Highboy]

Not necessarily.

If you have an aftermarket radio or other accessory, you could have a power draw from it.

[Nitekruizer]

I would check to see if anything in the truck is staying on first, maybe a glove box light or something like that. If it's an electronic regulator, I've had them go bad and allow the battery to drain through the alternator's field coil (rotor windings). This would be more than just a slight current draw though. Hope this helps.

[TLXregnar07]

Well now I don't know what to do next. The battery that was fully charged last night is dead now. I have some conductivity between negative cable and the positive, even with the negative cable off the battery. Field coil of alternator has around 115 ohms against negative. I'm still leaning to shorted regulator, since unplugging it raises the resistance reading dramatically.
I'm about stumped. If I charge the battery it will crank and show charging voltage at the.battery.

[Nitekruizer]

Well, until you get another chance to work on your truck, I would suggest disconnecting the battery while the truck sits overnight to prevent a possible electrical fire.

• Next time you work on it try pulling one fuse at a time to see if the electrical drain on the battery goes away. If it does then you've found the faulty circuit.

• Probably the easiest way to find out if the VR is bad would be to try another regulator that you know to be good. Although when my regulator failed I noticed that if the truck sat for a couple of hours, the battery, the positive battery cable to the starter relay, the wiring harness to the alternator and the alternator itself all became very warm to the touch. The battery would go dead in just a few hours. The transistor in the regulator failed allowing current to flow from the battery through the VR to the rotor winding in the alternator. I've had several of those parts store replacement electronic VR's fail this way.

[TLXregnar07]

I disconnected the battery cable. I've pulled the one fuse that should be ignition off hot, and checked all the others for any voltage, all read zero.
That, plus the only repair I made was to replace the fusible link, makes me believe the problem is under the hood, somewhere in the regulator/ alternator area.
Whatever it is, it happened all at once, since the battery discharge had never happened even with it sitting for weeks, until that day this all started.
the effect that the fusible link burned up, tends to match the syptoms of shorted regulator, also.

[Nitekruizer]

Well now I don't know what to do next. The battery that was fully charged last night is dead now. I have some conductivity between negative cable and the positive, even with the negative cable off the battery. Field coil of alternator has around 115 ohms against negative. I'm still leaning to shorted regulator, since unplugging it raises the resistance reading dramatically.
I'm about stumped. If I charge the battery it will crank and show charging voltage at the.battery.

• If you have charging voltage at the battery how many volts do you have at idle? If you increase the RPM to 1500 then to 2000 does the voltage increase, and if so, by how much? Voltage should not climb above 14.5 - 14.7 maximum. If you're getting 16 volts or more the VR is bad. However, when these electronic VR's fail they can also cause a "no-charge" condition as well as an "overcharging" condition. Yeah,they will fail without warning, one minute they're working then all of a sudden they're not.

[TLXregnar07]

I think I may have found the issue.
Friday night I changed the voltage regulator, and charged the battery up. I saw no current flow when the cable touched. when the truck was running, was showing around 13.8 volts or so. Battery was fully charged Friday at 9PM, so I took the battery charger off and the truck was left to sit. It started fine at 7am, 12:30, and 7:30pm Saturday, 9:00am Sunday. Each time was just a crank and start run 3-4 minutes then shut off. It was then left to sit all day Sunday and all day Monday until I started it last night around 8:00. I'm hoping it 's fixed now. I still need to replace the radio capacitor on the regulator, which the local dealer should have in later this week.
Maybe it's fixed finally.