Ford 3000 Power Draw Causing Stall

[sweetskillsrk]

After a lot of planning, studying the schematic, and running wires, the lights on my 3000 are finally working...sort of. Both headlights and the rear work light do work, but when I pull the light switch, the tractor stalls. I don't have the original lights on it right now, but I hope to soon. I had some other lights in my shed that are very similar, but have a toggle switch on the back of them. When the tractor started to stall, I pushed the light switch back in and the engine revved back up and started idling again. I ran up front and cut both lights off at the toggle switches, pulled the light switch back out, and then went and cut the lights on separately with no issues. I assume the lights are drawing too much power when initially turning them on? I read somewhere that this could happen because I pulled power off of the start switch? That is how the schematic is drawn so that's what I followed. Would a relay help at all or should I rewire it and bypass the start switch? I'd rather not do that so it stays accurate to the schematic and so it's as original as possible, but I'll do what needs to be done. Any advice is appreciated.

 

[wore out]

You must be pulling current for your lights through the ignition switch?

Sounds like the ignition switch may be getting weak, but no matter, rewire it so the light switch gets battery power without involving the ignition switch, and fuse the power lead accordingly, likely at 25 Amps.

 

[Sean in PA]

I assume that it has a gas engine, correct?

If turning on the headlights draws enough current to drop the voltage at the coil to where it stalls, then I don't think moving them to their own wire from the battery would help. I am thinking that it might have too much resistance in the circuit for the coil primary so that it is barely making a good enough spark without the extra draw of the lights, or possibly the coil is beginning to go bad.

Disconnect the wire coming from the key switch at the coil and measure the resistance across the small posts of the coil with an ohmmeter. Also measure the resistance from the end of the wire that you disconnected back to the key switch. The coil should measure either around 1.5 ohms or 3 ohms. If it is 3 ohms then you should not have any other resistor or resistance wire between the key switch and the coil and that wire should measure 0 ohms or very close to it. If the coil measures around 1.5 ohms, then it should have a resistor or resistance wire between the key switch and the coil so that the wire measures another 1.5 ohms. I suspect that it might be a 3 ohm coil with another 1.5 ohms of resistor or resistance wire in line with it.

 

[Bern]

A relay would help but all you'd be doing is putting a bandaid over the problem. Since you want it to remain original let's
figure it out. You very likely have a poor connection somewhere between the power source (battery) and the light switch
circuit. If it were me I'd be doing some voltage drop testing between those two points. Alternatively, look for loose or
corroded connections in the circuit feeding the light switch, starting with the two B connections at the regulator.

 

[Eman85]

Put a voltmeter on the battery and take a reading, then start the tractor and see what the voltmeter does.

 

[sweetskillsrk]

All good info, thanks for the replies. And yes, it is gas and it still has the original generator. Maybe the generator is getting weak? Do you test a generator like you would an alternator? I've been thinking about swapping it to an alternator but haven't needed to so I saw no reason to do it until the generator failed. I'm not super worried about staying original, but makes it much simpler so it matches parts books, service manuals, etc. I have seen so many tractors and machines over the years rigged, cut, spliced, bolted, and taped back together, I'm a little particular as to what I do to my tractor.

I know I have good grounds as I tested them all before finishing the project. 0.3 Ohms at the grounding points and a good circuit from negative post to ground wires. The key switch is no more than 2 years old so I doubt that has anything to do with it, you never know, but unlikely. I'll check the coil, which I am having some falling RPM issues/stalling issues while running at 1800RPM, both with and without mowing. I assumed it was a fuel delivery issues. As for the lights, I can check voltage drop. I used individual 16 gauge wires for each light, not fed off the same wires so they should be getting enough voltage to handle the lights. Testing to come.

 

[Sean in PA]

I used individual 16 gauge wires for each light, not fed off the same wires so they should be getting enough voltage to handle the lights.

The gauge of the wire has to do with how much current can be delivered, not voltage.

 

[Hemmjo]

(quoted from post at 05:06:16 08/10/23)

I used individual 16 gauge wires for each light, not fed off the same wires so they should be getting enough voltage to handle the lights.

The gauge of the wire has to do with how much current can be delivered, not voltage.

This is not totally true. Current and voltage are directly related. You cannot have current without voltage. Wire gauge affects the how much current a wire can safely carry. Wire gauge also affects resistance in a circuit. Resistance affects voltage. Resistance rises as wire gets smaller. Pushing more current through a circuit always increases voltage drop. Larger wire, less voltage drop. More current at higher voltage is available were it is needed.

Testing voltage at the end of a long small wire and an large wire of equal length will be the same with NO current flowing. But as soon as you load the circuits, the voltage will drop more on the small wire than the large wire.

As mentioned in a previous post, if the ignition circuit is already at the low limit of voltage, any additional current draw can cause the voltage to drop below the threshold of functionality.

The point is, RESISTANCE affects voltage drop. Someplace in your system, you have something creating resistance between you ignition system and your. When you turn on the lights, you increase current though that location. It can be a small wire, corroded terminal screw, defective switch, or a combination of a couple of these. It can be anything the current flows though on it way to your ignition circuit.