The Stovebolt Site Forums The Shop Area The Electrical Bay dead battery (voltage regulator)??

Hi folks.
I just brought my new 1948 3/4 tonne truck home, and I love it! It runs great, and drives great to boot (aside from the brakes not working).

Anyway, when I first got the truck it was having a hard time starting, which caused the battery to be drained in attempting to start it. Now it starts up nicely when I use a charged battery, but it doesn't appear to be charging the battery when the engine is running. The battery gauge in the cab reads just on the negative side.

The truck has what appears to be a new voltage regulator in it, but there is one wire not connected, and just dangling in front of the terminal on the voltage regulator labeled BAT. It obviously is supposed to be connected, but when I do connect it, the gauge reads way down in the negative side.

I'm planning to switch the truck over to 12 volts, but have other things that are higher priority at the moment, so I would like a functional 6 volt system for the moment.

Is it possible that I have the wrong voltage regulator, and is there a way to find out? I can take pictures of it if requested.

Thanks so much for all the help!

Tom

I agree with you that getting the 6 volt system working first is the best approach. Likely you have a problem that will cause the same issue in a 12V system. And if you do a conversion before fixing this issue - you just have a lot more stuff to possible consider (ALL the 12V mods you made).

The disconnected terminal is a good place to start. I'd think the previous owner disconnected this due to a problem he couldn't solve. Likely there is a short in the system, which you see when you reconnect the wire and see the current drain.

I don't think a wrong regulator would cause this power drain (with ignition off). However a stuck relay in the regulator certainly could. Pull the cover from the regulator and make sure all the contacts are free, and not welded together. Disconnect the battery first and press the contact with your finger and make sure the relay contact can 'make and break' freely. Also look at the relay contact surfaces and see if they are reasonably clean.

If the relay contacts look OK, connect the disconnected wire, and POLARIZE the generator (short the regulator GEN to BAT terminals for a second or so). See if this corrects the problem.

If not, you neet a voltmeter to dig deeper. Disconnect either connection to the battery, set the meter to AMPS, and check the current drain with the ignition OFF. You should not have any current in this configuration.

If you DO see a current drain at this point, you have a short in the system you'll need to find.

Finding a short can take some time. A schematic of your car will be of immense help in the diagnosis. Potential culprits include lamp sockets, door lamp switches, cigarette lighter, etc. The schematic will show you where you can disconnect circuits one at a time to find where the problem disappears - thus where you should dig deeper to find the real problem.

A possible time (and brain) saver would be to 'shotgun' the trouble shooting. Look carefully at all connections, 'jiggle' wires while watching the current drain, and you might find the problem in short order without having to go the logical deduction/engineering route.

Take your time, be patient, and remember that careful diagnosis will not only solve the primary problem - but will reveal other problems waiting to happen. Cleaning up potential issues now will prevent gotchas tomorrow.

Keep us posted, and if you have ANY questions, about using a meter to read current for instance, please don't hesitate to ask for help. Lots of good folks here are glad to assist and share our knowledge.

Good Luck!

thanks very much jgalt_54-235!
I'm going to work on this problem today, but i have a question. when the truck is in neutral and idling, what should the battery guage read when everything is in working order?
thanks again

tom

Check out the picture of a regulator in my tech tips article. The far left part, as you're looking at the regulator assembly with the top off is the cutout relay. It's there to prevent the battery from discharging itself through the generator when the engine is stopped. If it's getting a heavy discharge when you touch the battery wire to the regulator terminal, it's almost certainly got a set of stuck cutout relay points. It's nearly impossible to clean up those points where they won't continue to stick, so you'll probably need to replace the regulator, no matter how new it looks. TEMPORARILY, you might be able to clean up the points with very fine sandpaper, like 400 grit or so, but don't get complacent and think it's a permanent fix. One episode of a stuck cutout relay that you don't notice right away will fry your generator, and might result in a fire that destroys the vehicle!

If you can get the cutout relay points clean enough to work without sticking, disconnect all the wires from the generator and put a voltmeter between the Armature terminal of the generator and ground. Start the engine. Slowly increase the engine RPM while watching the voltage output at the armature terminal. it should top out at about 2 volts. If there's no voltage, momentarily attach a battery hot wire to the Armature terminal, for about one second or so. There will be a pretty big spark, so don't panic! Recheck the voltage while the engine is running. If it's there (2 Volts of so), connect the wires and proceed with your diagnosis. if not, remove the generator and get it checked out and rebuilt.

Confused yet? Check out the generator as I've described above, and post your results.
Jerry

Alright, well, I went out this morning to get to work on it, the first thing I did was take note of the current condition with the truck idling and with the truck off.

I then took the cover off the voltage regulator and pressed the connections with my finger to attempt to free any stuck connections. That worked like a charm. Everything as of now is working properly. when I connect the dangling wire to the BAT terminal the battery charges.

My concern now is why the connection got stuck to begin with, and what will prevent it from happening again?
Can the connection get stuck again and fry the generator while I'm driving down the road, or is it most likely to happen when I start the truck in the morning?

The cutout relay is supposed to spring open from its own spring tension, plus a reversal of the polarity of the magnet when the engine stops and current tries to flow backwards through the generator windings. If the points are a little sticky, the connection stays made long enough for the cutout relay to re-energize in the reverse direction, and hold the points closed while discharging. That's why I don't reccomend cleaning or filing the relay points. It's almost impossible to get them smooth enough to separate cleanly when the current tries to reverse.

One very important adjustment is "closing voltage". The cutout relay should not try to close until the armature voltage reaches at least 7 volts. This can be checked by slowing the idle down until the armature voltage is 6 volts or so, and carefully increasing speed until the points close. This assures the generator voltage is high enough to charge the battery, not allow it to discharge through the generator. When charging against a fully-charged battery, the voltage regulator (far right of the three coils) should be adjusted to 7.5 volts. If you don't have a very accutate volts-ampere tester, get an experienced charging system shop to make the adjustments.
Jerry

That problem got fixed a lot faster than I imagined!

Stuck relay contacts are 'welded' together. A spark jumps the gap just before the contacts mate, and the spark heats the metal. Enough heat and they stick. It's the nature of the beast, and while there are several ways to minimize the arcing (spark), I wouldn't think you have any other electrical problem(s) that would have caused this.

Old contacts that are dirty and pitted are more prone to getting stuck. You can clean the contacts to a flat surface if enough metal is left, but if you do this - it would be good to adjust the regulator correctly so your charging system is in optimum condition.

If it's an older regulator, I'd consider buying a new one, and clean your old one and keep for an emergency spare. I think $35 is about the going price. A new one would be already adjusted and should be problem-free for many years. And having a spare you can slap on is a good idea.

Once I had a regulator malfunction on a long trip, which caused the amp meter to go to high current pull (welded contact causing max drain from the generator). I found out the hard way that running this way for even a short time caused the generator armature to sling out solder and then die!

You asked about normal amp meter indications at idle. Assuming your battery is fully charged, you should see only a slight 'tic - tic' on the meter at idle. Perhaps slightly on the negative side if it's a low rpm idle. A faster idle give a higher 'tic' rate on the positive side of the meter.

A slightly discharged battery will show a strong 'tic', higher in the positive side until the battery is recharged - then it's back to the slow, soft 'tic'. Leave the lights on for a minute, then start, and you'll see perhaps 2 minutes of high charge.

thanks jgalt_54-235
as it is right now, the battery is almost totally dead. i cant start the truck without boosting it with a 12 volt battery. once its running the meter shows a strong charge, but i suppose thats because the battery is nearly entirely drained.
when i boost the truck from a 12 volt battery i remove all of the fuses from the truck. is this the best way to do it?

If you have an original-equipment generator, the part number should be 1102667, with a regulator part #1118201. Adjust the current regulator for a maximum output of 30 amps, and the voltage regulator to 7.5 volts AGAINST A FULLY CHARGED BATTERY! The voltage regulator setting will drop slightly when the cover is installed, so adjust the voltage to about 7.7 or so, then install the cover and recheck it.

It's not really necessary to remove all the fuses to boost start with 12 volts, especially if you apply the voltage to the starter motor only. It's going to be a lot simpler if you recharge the battery, or install a hot 6V instead of trying to recharge it with the generator. It will take a long time to build up a 6V battery with a generator, because the generator is designed to maintain charge, not recover a low battery. Invest in a good battery hydrometer, and keep a close check on the charge. A fully-charged battery should have a specific gravity of at least 1.265.
Jerry