The Stovebolt Site Forums The Shop Area The Electrical Bay ammeter question

can someone tell me if the wire hooked to the guage should have power to it all the time even with the key off, and if not, and suggestions to what could be going on. Have had a problem with starting, would not start yesterday, and today it started no problem. Something seem to be draining the battery,When you start the engine, the power wire to the ammeter in dash gets hot, in only a few minutes of running. I am stumped to what is going on.

shmkr

Both wires connected to the back of the ammeter will be powered all the time. Both terminals have a direct connection with the battery...the ammeter is the main conduit for current flow in the charging system.

If your battery is discharged and you start the engine, the generator or alternator will attempt to re-charge the battery, which is done through the wiring at the ammeter. If the wires get hot or warm, this would indicate a large current flow, but your ammeter should show this. I would think for the wires to be 'hot' the needle must be pegged for sometime.

This isn't normal, obviously. I would disconnect the battery and make sure the connections on the back of the ammeter were clean and very tight. I don't know what kind of truck you have, but if it's an old Stovebolt, there are not many things that are not switched with the key that could be draining the battery.

A battery plate can short internally and cause the battery to discharge, or something in the horn circuit could be going to ground through a high resistance...this circuit isn't switched.

Check and clean your cables and connections, do a voltage test on the battery before you start the rig, then one when it is running and charging.

Watching the ammeter should tell you if things are going nuts or not. There can't be mass amounts of heat generated (usually) without large current flows.

Do some more detective work and let us know what develops.

Stuart

ok first off the truck is a 1946 chev pickup/have done a voltage test when truck is running it shows almost 6. When the battery is fulled charged, it is reading around 7. This is my 4th battery is just over 3 years. The guage is only showing one line above center, unless the guage is not reading correctly, which it is the original.But I think it reading because when it stops charging, it goes to the discharge side. Been looking for a wiring diagram for the instrument panel, to see if something in the dash in not hooked up wright or maybe backwards, any suggestions would be greatly appreciated, and I will check the horn circuts

shmkr,

A functioning charging system will show 7 to 7.4 volts or so at the battery when the engine is running around 1500 RPM. This is what it will take to keep a 6 volt battery fully charged.

I have enclosed a nice link to a bunch of wiring diagrams. Find your year and click on it. If you have lost 4 batteries in three years you surely have a problem. Keep in mind that overcharging can kill a battery the same as a constant discharge/recharge condition.

There are very few fuses on these old rigs, so any external drain on the battery would have to be of a high resistance or the truck would probably have gone up in flames long ago.

If the battery is in a compartment under the floorboards, look for telltale signs of gassing. This would be from overcharging and would show up as a white crust in the area around the battery.

The voltage regulator controls the charging system, and if you are overcharging the battery, this would be the prime suspect.

Take a look at the wiring diagram and see if it helps.


http://chevy.oldcarmanualproject.com/electrical/wiring/index.htm

Stuart

I've got another suggestion that would explain the chronic undercharge condition of the battery, and the hot wire. Take the wires off the back of the ammeter one at a time, and throughly clean the contact area. (Disconnect the battery ground cable first.) If there's a loose or dirty connection at the ammeter, it will generate heat, and also fool the regulator into cutting back the generator output, resulting in an undercharged battery. Try measuring the voltage output at the generator Armature terminal with the engine at a fast idle 1,500 RPM or so, and again at the battery positive post. The two readings should be within 2/10 volt of each other. If there's more voltage drop than that, you've got dirty points at the regulator cutout relay, or a loose or dirty connection at the back of the ammeter. Either one will result in a chronically undercharged battery.
Jerry

thanks guys, I will give that a try and see what happens. I have had mechanics look at the truck, an alternator shop, and still can't find the problem. It's just weird, it seems to be alright for a while, charging great, starting great, and it goes for a crap, won't start,the battery's dead. It did that on the weekend. Started fine in the morning, took it out, stopped for a while, won't start, acted like the battery was dead, pushed it and got it going and brought it home. Next morning started right up? Have checked for loose connections till the cows come home, and haven't found a thing.

Voltage regulator ??

You might try taking both battery connections off, give them a good cleaning with an inexpensive terminal cleaning tool you can get at any FLAPS then put them back on and make sure they're tight.