Voltage regulator or alternator problem?

[gnalan]

I've had my alternator tested a few times over the last week and each time I was told it was fine but that my battery was low and needed charged. I just put a brand new battery in it hoping that would fix it, but it's still idling rough and only showing 13.5 volts.

[gnalan]

Just had it retested and was told the voltage regulator was bad. Can I just replace the voltage regulator on the alternator, or do I need to install a brand new alternator? Is there a way to test to see if the alternator is good or bad and that it is only the voltage regulator?

[scot850]

What is the mileage on the car? Often it is only the brushes on the regulator that wear out and you can just clean the stator and replace the voltage regulator portion. The only other thing that can go out are the bearings. If they are not noisy then replacing the regulator only makes sense.

Some will see that the effort to replace the voltage regulator makes more sense just to swap the whole alternator.

13.5V is a fairly healthy charge from an alternator. When it was tested was everything switched on, like headlights, heater fan radio and other stuff? My buddy thought he had alternator issues but it was a bad battery. He registered 13.2-13.5V. When he switched off all the items the charge went up to 13.8V

Neil.

[gnalan]

Mileage is under 183k miles.

I had the fan turned all the way up, plus the rear defroster on, when they tested it. I didn't put any load on it before when I had it tested.

I just put a brand new battery in it this morning. I'm getting a voltage of 13.5 to 13.8 at idle, without putting a load on it other than the headlights being on.

One thing I've noticed is when the voltage gets low that I get an error message for a right signal bulb failure (front right bulb), but when I have a full charge the bulb works just fine. That's the only problem with any of the bulbs or turn signals is the front right. That seems very odd to me.

The battery light has not come on at all, nor has any messages about the charging system.

[gnalan]

Been driving around most of the day, and so far everything seems to be ok. Check engine light went off on its own, and I'm getting a reading at idle of 14.1 volts last I checked. Could it be that the voltage regulator only acts up on hot days, and on cooler days can work fine? I don't want to throw parts at it if they're not needed. The battery had a bad cell, so it needed replaced (thankfully it was still within the 60 month prorated warranty period and only cost me $37 instead of $100).

Between city driving, sitting idling for long periods of time, and shutting off the car and restarting it more than a dozen times, I'm still seeing a reading of around 13.8 volts. Heat was on part of the time, and radio was also on while sitting idling (the longest time being around an hour), and all seems to be working as it should. No battery light has ever come on, or any info saying anything about the charging system not working.

I'm still getting a message every now and then about the front right turn signal bulb being out, but after driving the car a little bit the bulb works just fine. I'm wondering if the bulb isn't working because of low voltage reaching the bulb, and then working fine when the voltage comes up, or if the bulb is close to blowing. (Had I thought about it earlier I would've swapped it with the left side bulb to see if the problem stays with the bulb or the location. That'll be my next test.)

[gnalan]

It's snowing out, so haven't gotten a chance to swap bulbs side to side to see if it's the bulb or something else going on.

Alternator and voltage regulator seem to be working ok, at least in the colder temps. Once it warms back up again I'll see if the extra heat causes the problem to come back. A couple of days ago I was getting a solid 14.1 volts at idle (with outside temperature in the 40s).

[gnalan]

It was cold this morning, and after starting it up I had a solid 14.6 volts up from 12.6 volts with it off. After it warmed up outside, and under the hood, the voltage dropped to 13.8. Everything is working as it should, so I'm going to assume everything is ok with it.

[gnalan]

I swapped the front turn signal bulbs left to right, and right to left, to see if the bulb failure message chased the bulb and it didn't. It still has an intermittent right front turn signal not working. I usually notice it after driving with the radio on, which seems odd. It still seems like an electrical issue. Is it possible for the alternator to put out the correct voltage but not enough amperage? Would a new voltage regulator fix this issue or would I need to replace the entire alternator?

[br0dy519]

Kind of sounds similar to my bad starter that was causing EMI(interference and loss of comm. to some of the modules). Humid, hot weather can exagerrrate that issue. Have you done a parasitic draw test? I’ve heard bad alternators can often cause that.

I would replace the whole alternator and see where that leaves you. Not a bad time to do the thermostat and PCV if you’ve never touched those. Only accept alternators with genuine Bosch branded regulators. I had to do the job 3 times because of aftermarket regulators and it was more frustrating than it needed to be.

[gnalan]

I've already done the PCV system when I replaced the ETM and the injector o-rings, and I replaced the starter when the original one finally died. I replaced the battery, too, after the car sat while I was laid up in bed. Just swapped in new Beru plugs and new Bosch coils to get rid of a misfire.

I'm slowly fixing what needs done when they creep up on me. Most of the parts are still the original parts that were originally installed from the factory.

How do I do a parasitic draw test? I'm assuming there's a way to check the amperage output from the alternator, but I don't have the equipment for that. If I don't need to pull it, I'd rather not. It looks like I can swap the regulator with the alternator still in the car.