The Stovebolt Site Forums The Shop Area The Electrical Bay Generator light flashing--battery running down....

How do I check to see if my generator/regulator is charging? My battery is running down. I changed a cheapo fan belt for a better one, charged the battery but there is still a problem. The generator light keeps flickering even when I'm booting it hard. An expert at my local garage said 3mths ago that my generator was charging but why's the light coming on?
Can I check it when the battery is flat?

start by checking every connection in the system, could well be a loose on making only intermittant contact

Bill

6 volt or 12? The same diagnostic procedures apply either way, but the result numbers will be different. The flickering no charge light probably means the cutout relay in the regulator is opening and closing for some reason, possibly dirty points on one of the regulator coil contacts.

Disconnect at least one battery cable, and remove the top of the regulator. It's usually held on with two small sheet metal screws. There will be three sets of coils inside, one with a large set of points that will be open with the engine off. The other two sets of points will be held closed by a small coil spring. Take a clean piece of file card stock or a business card, and gently rub it between all three sets of points, changing positions frequently to expose clean areas of the paper. DO NOT use any type of sandpaper or a file! Once all the points have been cleaned, crank up the engine and observe the operation of the points. The normally-open set (the cutout relay) should snap shut as soon as the engine starts, and the idiot light should go out and stay out. If you gently push either set of normally-closed points open, the cutout relay will snap open and the dash light will stay on. As soon as you release the held-open point, the system should go back to charging.

Any operation other than point cleaning inside a regulator should probably be left to someone who is thoroughly familiar with generator/regulator system adjusting. We're getting to be sort of a dying breed! It's possible to adjust the air gaps on the point assemblies, the closing voltage on the cutout relay, and the current and voltage limiting points, but it takes a couple of special meters, and a tool or two that some shops don't have. As a matter of safety, it's always a good idea to at least remove the Battery wire from the regulator, or to take one of the cables loose at the battery before installing or removing a regulator cover. One slip, and some nasty shorts and permanent damage to the regulator can happen.
Jerry

Edit: It'd s possible to check system operation with a discharged battery, but it's better to do any adjusting other than setting the current regulator against a fully-charged battery. it's possible to get some really off-the-wall voltage numbers if the generator is running at its full capacity to recharge a low battery.
Jerry

The charge indicator light is wired through the ignition switch, so any resistance in that circuit will cause the light to flicker or remain on, either dimly or possibly at full brightness. If the condition is only the result of resistance in the light circuit, the generator should still function fully. What you describe seems to be low or irregular output from the generator, likely worn brushes, or badly worn or loose commutator bars (worn brushes are the preferred cause).

A quick check on the generator is to ground the field terminal of the generator while you run the engine at a fast idle: if the indicator light goes out, the generator probably is functioning properly; if the light continues without much change, the trouble is either the voltage regulator or the light circuit. Clean the regulator contacts as Hotrod Lincoln says, and temporarily connect a jumper wire from the regulator frame to the battery ground. If the ground wire corrects the problem, remove and replace the regulator, making sure the bolts are clean- those are the ground. Also check for satisfactory body-to-frame grounds.

A quick, but somewhat inconclusive, check of the ignition switch is to wiggle the key cylinder when the light is acting up. If anything changes, there is a loose terminal in the switch- not uncommon.

Without a wiring diagram, all this is somewhat speculative. What year is your truck?

I'm also assuming you are talking about a DC generator, not an alternator. Is that correct? The cause of trouble and the remedy will be different, depending on that.

Harvester

Harvester,

If you ground the field to test the generator and the "indicator continues without much change" why are you ruling out the generator...you haven't proved it works yet, right! Am I missing something here?

Stuart

Stuart,

No, you are correct: grounded field, no change- generator is suspect. Not sure what I was thinking with that line; maybe just too hasty and not enough proof reading. Glad you caught that.

Harvester