another electrical problem

[maddawg308]

This is on Rusty - I'm inclined to just sell it as is, I'm not making any money on her, really. But if it's simple, I'd be more than happy to fix it and make the new owner happy.

Batts are dead. Truck starts and runs real well with a jump. However, when the truck is running, there is still no power for anything - lights are dead, blinkers are dead, horn dead, gauges (except for the tach which I believe is mechanical only) are dead, battery not charging. When the truck is shut off, once again needs a jump to start.

I checked all the electrical and I don't see any major wires messed with, the alternator is hooked up right. This had a radio installed in it, a RT-524 series, but the cables have all been disconnected for a long time. Only electrical faults I see are a couple cut wires going to the heater, everything else looks good.

Where should I start testing things with the multimeter?

 

[ARMYMAN30YearsPlus]

Mike:
I would start with the batteries and go up the wiring harness from there. Use the TM because the wiring is too complex for any mortal to memorize it and track down a fault. Sounds like you have an open circuit somewhere. Is the voltage gauge showing any voltage when it is running?

 

[Blood_of_Tyrants]

It is probably something basic. Start with the main power switch wth good batteries or another vehicle for power. Most likely, you will find that there is no power on it. Head upstream and find the bad part or loose connection.

 

[OPCOM]

there is a wire from the magnetic start relay (on the engine near the oil sender) labeled "10". it gets power (as does the relay) from wire "14" on the same stud. If the truck starts, "14" has power.

The magnetic start relay gets energized by wire 74A, which is energized through the start switch, which gets power from wire 74.

wire 74 joins wire 27. wire 27 comes from the power switch and is energized when it is ON.

Wire 10 also goes along and becomes wire 11 which goes to the power switch. Wire 11 supplies the power switch.

Note the power switch has two outputs. 11 is the input for both, and goes to terminals A and C.

The output of the power switch that supplies cranking control etc is terminal B. That is where wire 27 is attached.

The other output of the power switch supplies the manifold heater switch and also supplies power to make the alternator work (turns it on). It is terminal D and wire 1 that goes to the alternator (the small wire of the alternator). The manifold heater switch is supplied by 35 also coming from terminal D.

So, if you have no charging with the truck running and the power switch on, check for 24V at terminal D (wire 1).

If you have no guages, check for 24V on wire 27. Note there is a connector in wire 27 that connects it to the guages separately from the cranking pushbutton switch. Maybe it is unplugged or the contact is loose.

If you can crank and yet the air buzzer does not sound, then the wire 85 may be unplugged from the buzzer.
85 is connected via the air pressure switch to 27 from the power switch terminal B.

It is possible 27 has been cut or damaged in such a way that you can crank but have no buzzer or guages.

If you will check these logical things, it may lead you to the problem, and if not, if you will post the results what you did find, I can help. I can easily read the schematic and help you. The CAD version of the schematic is posted in the file section. Thanks to whomever did it!

 

[Recovry4x4]

I'm somewhat interested in Rusty if I can get my little tractor that could sold. Got more pics?

 

[nickd]

Opcom, that is an outstaning trouble shooting guide! The manuals should be that easy to understand! Mike, let us know how you make out and where the problem was found.

 

[acetomatoco]

I would first see if the intank pump is running when you turn on accy switch...that will tell you if all power is dead, or just some of it. On the outset it just seems that the accys are not getting power. I would just use a test light and start following from the positive post of #2 battery...aka 24 volt output and see where the open is...of course, the first thing to do is put in two good batteries....you may have a bad cell which is not allowing the circuit to complete .....aka an open battery...

 

[OPCOM]

Thanks nickd, I only want to help. Since I am not so expert mechanically, the electrical stuff is where I can contribute. I bet the issue is fairly simple, just 'hidden'. The wires in these old things are often frayed and since there are few breakers and no fuses where there should be fuses, a short on a small wire would just burn the wire in two, possibly damaging a switch or something. Going down the road, the burning smell from such an event might only be noticed for a few seconds and possibly attributed to a passing hooptie.

Mine has alot of little cracks in the insulation on the wires from the turn signal plug going into the harness. I'm going to pull it loose and coat the bundle and as much as I can reach inside the bundle in silicon glue to help stop the deterioration. I suppose it will be a work of art.. but that will keep the insulation in place and protected, since the only other thing to do is replace the harness, which is really not nescessary. I think it is that way from being in the open versus covered up like the rest of the wiring.

The fuel pump power circuit - Pump is on #657, connects through a chassis wiring connector to #27 near the power switch, so it should run if the truck cranks. Right now I would bet that it's time to lie on the floor and look up into the dashboard on Rusty. A strong light and some careful fingers, might reveal the trouble.

 

[cranetruck]

Mike, Patrick knows what he is talking about....no question about that, but to do it step by step, just locate the "horn breaker" and make sure you have battery voltage on #10.
The schematic diagram is good, but the "ground" connections should be identified as "frame", "engine block", "firewall" etc..one should be able to identify ground straps and where they are located in the circuit. There may also be a problem with the way the starter solenoid is drawn.
The flame heater ignitor is more than just a coil, it contains a vibrator to produce a rapid succession of sparks. Well, I better stop, I'm too critical, sorry.

The circuit breakers should keep wires from melting. There is one inside the 3-lever light switch also, a 20-amp one.
Do you have an electric horn or is it an air horn?

 

[m-35tom]

if it starts with a jump, the batteries are dead. with dead batteries i doubt you will have any power anywhere to test. put in new batts and go from there.

 

[OPCOM]

Was this resolved?

 

[nattieleather]

Batts are dead. Truck starts and runs real well with a jump. However, when the truck is running, there is still no power for anything - lights are dead, blinkers are dead, horn dead, gauges (except for the tach which I believe is mechanical only) are dead, battery not charging. When the truck is shut off, once again needs a jump to start.

Going by your statement and assuming it is a diesel....If the truck fires up with a jump and you've disconnected from the power vehicle and you get no lights, no power to batteries, no nothing then to me it sounds like your altinator is not putting out. If you have gages and lights etc when the other truck is hooked up then once you unhook from it you have nadda then to me it sounds like a bad altinator. Because if the altinator was working correctly when you hooked the jump truck up you would have the required power to energize the altinator and get it producing volts. And assuming that it is a diesel you can have no power and it will keep running. Diesel don't need volts to keep running even if the in take pump isn't.

Now if you don't have any volts with the other vehicle still attached then you have some other issue going on.