Now I’m overcharging, My car is murdering voltage regulators Options

[VaccaRabite]

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I’ve been driving my car all over for the past week or so.
Last weekend I noted that it was hard to start, and it stalled while pulling away in 1st once. Weird. Didn’t worry about it and finished my drive.

Got home and I checked voltage at the battery and I was making 18 volts, my VR had seemed to fail and I was pushing max voltage at the battery. Geeze, no wonder the car was hard to start with the alternator at max effort.

So, I’ve done the ground thing and they are all clean and good. In my undercharging thread I ran a 10ga wire from the alternator case to the body ground point near the relay board in the engine bay.

I’ve also checked all my collection of voltage regulators and all 5 of them, be they mechanical or solid state are now allowing the alternator to go full bore all the time.

This is with both the brand new battery and the PC680 gell cell race battery.

What do I look for now? Could I have broken the VRs by pulling them off the running car while chasing issues with the alternator last time? Or is this a car thing and I need to fix something else.

The car is essentially acting like I have D+ and DF jumped with D- left empty.

Zach

[Jeff Hail]

Alternator connections:
D+, DF,D-, and B+.

D- terminal - Alternator housing ground. Is also the ground return from the VR.

Diodes:
D+ terminal -low output. Secondary output of alternator.
B+ terminal - high current. (also direct to battery)
Diodes on path 80 is common to both the D+ and B+.
This also links the ground loop for D+, B+ out.

If the diode out circuit faults at B+ voltage will fall at the high output side.
If the D+ diode faults voltage will fall on the low output side.

Charge lamp:
D+ connected to charge warning lamp and ignition switch, voltage sourced from battery.

This is fused at #9. Charge lamp bulb should be 2 watts. Less than 2 watts will not excitate the field properly. For troubleshooting purposes the VR cannot determine voltage at both diode circuits. The VR is primary to the low output on D+. Any low voltage difference between B+ and D+ will keep the charge light on.

The charge lamp will have 12V current on the switched side and ground from the field. Boot strapping is managed through the charge warning lap and ignition switch at D+ as the alternator cannot excitate on its own.

Starting and Running:
Upon engine starting no output from the B+ or D+ terminals should be available. The VR closes D+ and DF. D+ drops to low resistance via field.
Working properly the alternator spins and creates a field which generates voltage at D+ and B+ that are the same then the warning lamp will turn off.

Running

Voltage regulator:
D+ voltage should be what you are seeing at the battery. As the ground drops away (charge lamps goes off) D+ and DF are now regulated.

I believe you already tried the regulator removed from the board and connected direct to the alternator connector. If no changes move on. To me this rules out both the regulator and board.

If you remove the VR while the engine is running the charge light should stay off as the voltage is still balanced at the diodes at D+ and B+.

Relay board:
Jumper 12V volts from the battery to the DF terminal at the board? This will let the alternator juice out to its highest possible output running. This will also confirm the diodes at B+ and windings are good

Alternator:
How are you checking the maximum output of the D+ circuit? This will be your charge supply to > the battery. Jumper D+ and DF on the board. Don't measure the voltage supply at the battery as you will have a false reading. Has to be measured before as close to the alternator as possible, then at the board but not past the board. This should show the maximum output of the alternator output on the D+ circuit.

Disconnect the jumper at D+ and DF. Running measure the readings again on the board at D+. Read the battery. They should be the same. If the voltage is high you most likely dropped a diode on the low output side and D+ is feeding back through the high voltage side of B+. This can appear as a ground loop problem when its actually the low side diode.

The charge light will turn off as its still getting voltage from both sides on D+ and B+ once the excitation starts through feedback trying to balance out.

I believe you a have a few things going on.

1) What wattage bulb is in the charge light? Did you install an LED or new bulb at some time? Should be 2 watts or less incandescent. If it's an LED go back to the incandescent as it acts as a resistor.

2) Double triple check the board. A short in or between D+ and DF will put the output voltage into boil your battery territory.

3) Double triple check the new harness. Make sure no two reversed wires. (Unlikely based on symptoms but worth checking again).

4) Ignition switch: Check from ignition switched power to the #9 fuse, fuse box terminals, wiring to the charge lamp circuit and back to the alternator lead connection.

5) Alternator - D+ side diode toast. Pull it and get it bench tested by an alternator/starter shop. If the alternator is good it will point you backwards towards a ground issue. (are you sure you corrected the ground issue in your undercharging adventure? Was it an actual ground issue or something undiscovered and still present?)

I can't see this many VR's all being bad. VR's are pretty durable considering the cycles they go through. One of the above may be killing them as a side effect.

Good luck Zach.