79 f250 bat problems
#1
11-26-2011, 12:12 PM
79 f250 bat problems
79 f250, i have a draw on the bat, so i put test light between neg cable and bat and started pulling fuses but the light still remained lit. anyone have any other ideas pl,ease help thanks
#2
11-27-2011, 12:16 PM
Removing fuses one at a time will not isolate a short. Given that you have verified that the draw on the battery is constant, and that it is on the service side of the fuse box, you can start looking for shorts or just bad control units from the fuse box back to the battery.
#3
11-27-2011, 12:18 PM
Removing fuses one at a time will not isolate a short. Given that you have verified that the draw on the battery is constant, and that it is on the service side of the fuse box, you can start looking for shorts or just bad control units from the fuse box back to the battery.
#5
11-28-2011, 02:34 AM
Do you have a wiring diagram
Yep. The service side is always the leg of the circuit that is bringing power to a point. The load side is/are those componets that use that power. There may be multiple service sides and load sides. As You Test circuits, you will find where the power is coming in and where it should be Used. If you can find a wiring diagram that would help you a lot.
#6
11-28-2011, 12:38 PM
i appreciate all the help but i started chasing wire today and couldnt find anything started to unplug connections looked for grounded wires and couldnt find anything could the regulator or ignition switch have a constant draw on the battery
#7
11-29-2011, 10:06 AM
hard to trace
Electrical problems can be difficult to trace 
Do you have a wiring diagram? If you do not have a wiring diagram then try to get one or at the very least make your own as you find your way through the circuits justy to keep track of where you are in the mess. Try this site to see if the wiring diagram for you truck is available 1973-1979 Ford Truck Wiring Diagrams & Schematics - FORDification.net
IDEA: Maybe pull all the fuses, and if the battery is still being drawn down then, with those fuses out, start looking from the fuse box back to the battery. BUT, look for systems that are between the back of the fuse box and the battery as the next step because those will need to be isolated one at a time. Once you have isolated ALL systems, if you have still not located a short or faulty system component, then trace the wiring that is left.
Thought, how about the starter switch? Is it mounted on the wheel well like on my 95' ?
Also, you said you are using a light between the negative terminal and the negative cable. What wattage is the light? is the light glowing brightly or dimly? if the light is glowing brightly it means that there is a very well connected short or something that is stuck on and mimicking a short. If it is bright, then try higher wattage bulbs to try to determine what wattage is being drawn from the battery. Keep going up in wattage until you find a wattage that dims. The bulb before the one that dims is at least close to the draw of the circuit that is at fault so this can help you locate the source of the problem by pointing you to circuits that use that wattage.
If the light is dim, then put in lower wattage bulbs until you find one that glows brightly. The first one to glow bright will be at least close to the draw of the circuit. Also, if the light is dim then there is the possibility of a not so well connected short, a loosely stuck switch, or a low wattage circuit that is the culprit.
Do you know how to convert from the wattage of the bulb to amperage? If so then cool but if not then do this; wattage = amps (voltage). The vehicle is 12v so just divide the wattage by 12 and you will have the amperage that is being drawn. Remember, you are using bulbs that are not necessarily exactly the wattage of the draw so your amperage calculation will be approximate.
The amperage will be important to know because electrical systems in vehicles use amperage rating and not wattage ratings.
Now, with all that said,
You could get an automotive quality multimeter and check the amperage with it the same way you are using the bulb. The difference will be you will not have to change any bulbs and you will not have to do any calculations because you can read it right off the multimeter 
If you have, or if you get a multimeter, to do this then also get another one to use in the hunt through the wires and components. Also, get some test leads with alligator clips to facilitate hooking to circuits. Make sure you get alligator clips that are small enough to get to the connections and make sure the clips are insulated. If you are not familial with these then look at Craftsman for the test leads and Craftsman for a multimeter.
Do you have a wiring diagram? If you do not have a wiring diagram then try to get one or at the very least make your own as you find your way through the circuits justy to keep track of where you are in the mess. Try this site to see if the wiring diagram for you truck is available 1973-1979 Ford Truck Wiring Diagrams & Schematics - FORDification.net
IDEA: Maybe pull all the fuses, and if the battery is still being drawn down then, with those fuses out, start looking from the fuse box back to the battery. BUT, look for systems that are between the back of the fuse box and the battery as the next step because those will need to be isolated one at a time. Once you have isolated ALL systems, if you have still not located a short or faulty system component, then trace the wiring that is left.
Thought, how about the starter switch? Is it mounted on the wheel well like on my 95' ?
Also, you said you are using a light between the negative terminal and the negative cable. What wattage is the light? is the light glowing brightly or dimly? if the light is glowing brightly it means that there is a very well connected short or something that is stuck on and mimicking a short. If it is bright, then try higher wattage bulbs to try to determine what wattage is being drawn from the battery. Keep going up in wattage until you find a wattage that dims. The bulb before the one that dims is at least close to the draw of the circuit that is at fault so this can help you locate the source of the problem by pointing you to circuits that use that wattage.
If the light is dim, then put in lower wattage bulbs until you find one that glows brightly. The first one to glow bright will be at least close to the draw of the circuit. Also, if the light is dim then there is the possibility of a not so well connected short, a loosely stuck switch, or a low wattage circuit that is the culprit.
Do you know how to convert from the wattage of the bulb to amperage? If so then cool but if not then do this; wattage = amps (voltage). The vehicle is 12v so just divide the wattage by 12 and you will have the amperage that is being drawn. Remember, you are using bulbs that are not necessarily exactly the wattage of the draw so your amperage calculation will be approximate.
The amperage will be important to know because electrical systems in vehicles use amperage rating and not wattage ratings.
Now, with all that said,
You could get an automotive quality multimeter and check the amperage with it the same way you are using the bulb. The difference will be you will not have to change any bulbs and you will not have to do any calculations because you can read it right off the multimeter If you have, or if you get a multimeter, to do this then also get another one to use in the hunt through the wires and components. Also, get some test leads with alligator clips to facilitate hooking to circuits. Make sure you get alligator clips that are small enough to get to the connections and make sure the clips are insulated. If you are not familial with these then look at Craftsman for the test leads and Craftsman for a multimeter.
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