Starter wiring help

[CMV]

83 JD 500C backhoe.

Electrical is 100 different kinds of screwed up on the machine. I had the starter relay (or solenoid relay or starter solenoid - I see it called several things but I"m not talking about the solenoid that's parked on top of the starter but the solenoid/relay before the starter & it's solenoid) bypassed. Small wire from start switch to solenoid (that's affixed to starter), main battery +12V direct to same solenoid. Worked for a while & now has finally died out. I still get a click from the solenoid but the starter motor doesn't even attempt to operate. Bought a generic heavy duty 12V 100A 4 post relay/solenoid/whatever you call it not to confuse it with the one mounted on the starter and wired that in, but no joy. Starter was weak already and would sometimes grind or turn for a second & stall out.

So anyway.....I have a new starter on the way that has it's solenoid attached. I also ordered the proper part # starter relay & it is also on the way. Since I'm not much of an electrician, figured I'd ask what to do with these parts when I get them. With the relay out of loop, I can't just follow the old wiring.

The way I THINK I should do it is this: +12V from battery terminal to either 'large' terminal on the relay, beefy cable from the other 'large' terminal on the relay to the 'large' terminal on the starter solenoid, small wire from battery +12V terminal to momentary push button start switch, small wire from other terminal on momentary push button start switch to 'S' terminal on relay. Now past that I'm unsure. Does another small wire go from the 'I' terminal on the relay to the small terminal on the starter solenoid or is it unused?

I also don't quite understand the purpose of the starter relay. Doesn't the solenoid mounted on the starter do the exact same thing + engage the bendix? I understand that the full starting amperage can't go thru the momentary push button start switch - it would fry instantly as small as the contacts & wires are. But how does that relay help anything? It gets the +12V signal from the momentary switch, closes it's contacts, & lets the +12V flow to the starter solenoid at high amps, then opens it contacts when it loses the +12V signal from the pushbutton opening the circuit and cutting off the high amp +12V to the starter mounted solenoid. I get that. But doesn't the same thing happen with the momentary switch +12V signal going straight to the solenoid mounted on the starter?

 

[CMV]

Worth 1,000 words.....

Top is what I had. Bottom is what I think I should have. Purple wires I'm not sure if they should be there or not.

 

[ovrszd]

If you don't get any results here, try putting your thread in the John Deere Owner Operator forum. Your hoe probably has the same starter wiring as the Ag tractors.

 

[LD1]

The I terminal is something that ford used a lot. The I stands for ignition, and supply's full 12v to the coil when cranking. Most ford coils don't run 12v normally, but at startup the hotter juice helps. For your application you can ignore that.

As to the purpose of the relay you bought, and yes relay is the correct term, (solenoids done work...like door locks or starter bendix, relays do not) I am unsure if you need it or not. Think of it as a switch to control high current with low current. The relay could be relaced with a large 100a+ switch that you manually actuate. But a relay just takes low current for the actuation.

So without seeing the setup, or knowing the machine, it is unclear if you need the high current going to the starter solenoid. Or if the solenoid also acts as a relay. Since you have a heavy gauge wire going direct from battery to starter, I am gonna assume the solenoid also acts as the relay and the 4- post one you bought is not needed.

 

[CMV]

I know "old way" in the pic above works. What I don't know is if it works well or is a durable setup. Maybe w/o the relay it's causing harm to the starter or solenoid and greatly reducing their lives? Or it may be simply redundant in a system with a bare bones electrical system.

Literally the only thing in the entire electrical system that I know of that works properly is the ignition key turns on/off the fuel solenoid. Absolutely nothing else is as it should be. I don't really care - I don't run it on roads or operate it at night. Would be nice if it charged it's own battery though..... luxuries....

 

[LD1]

I am leaning toward a relay being redundant. But shouldn't hurt anything. Just ignore the I terminal, make sure the base has a good ground, and wire battery to big terminal. Other big terminal to starter solenoid and key to S and it should work same as before.

 

[skyhook]

Here's my 2cents, there is no need for the relay in the second pic,
the solenoid on the starter does the same thing, on older Fords the starters had their "solenoids" mounted on the fender wall and not on the starter.
The starter in your first pic takes a small current from the ignition to the solenoid to activate the solenoid and open a path of larger current from your battery to the starter.
So I agree with LD1 in that the relay is redundant.

 

[Dave M7040]

I have pasted below an earlier post of mine which might give some trivial background info on what is happening electrically.

I would offer two possible explanations for the need for the additional relay.
1. The push button contacts, and the gauge of wire going to the push button may not be sized to handle the current the solenoid on the starter can draw. A voltage drop in the circuit going to the push button might be large enough that the starter solenoid cannot pull in.

2. The back EMF I explain in the material below can be in the order of hundreds of volts which is going to go somewhere. The flyback diode I also refer to is designed to safely bleed off this high voltage. Without the flyback diode, the smaller relay may be able to at least direct the EMF away from the push button where it might give a person a bit of a jolt

The most practical test I would do before concluding that the starter is bad is to use a volt meter. Any cheap one is adequate. Should cost less than $20. Measure the voltage where the starter solenoid connects to the actual starter motor with the other meter clamp connected to the battery ground post the battery ground as someone turns over the tractor. If the voltage drops to around 10 volts something is wrong and not even a new starter will work. If you do this and have some voltage numbers we can discuss possible causes.


Earlier post dealt with topic "Re: Relay switch seems to keep Failing."

One small part that is often overlooked when dealing with multiple relay failures is the Flyback diode.
When the coil inside a starter solenoid is activated or deactivated it generates a high voltage pulse of electricity called, in technical terms, ``back EMF or electromotive force.``
Manufacturers in recent years have provided a diode to bleed off this voltage so that nothing else is damaged. Usually the damage is done to a small relay used to activate the starter solenoid.
The biggest challenge is finding the diode in the wiring harness. Youtube will have lots of examples on testing diodes.
The first image is a small portion of the Kioti wiring diagram showing the diode.
The second image if from a Kohler powered zero turn mower also showing the diode.
Hope this may give you one more thing to check out.

Dave M7040

 

[Leejohn]

Sten drive boats are wired like your right way picture without the big gray wire and the I wire goes to coil with standard ignition, like was said you don't need it. I ask the ? about this in service school and I was told, it's was to be able to use a smaller wire when running a long ways.

 

[Xfaxman]

83 JD 500C backhoe.

Electrical is 100 different kinds of screwed up on the machine. I had the starter relay (or solenoid relay or starter solenoid - I see it called several things but I"m not talking about the solenoid that's parked on top of the starter but the solenoid/relay before the starter & it's solenoid) bypassed. Small wire from start switch to solenoid (that's affixed to starter), main battery +12V direct to same solenoid. Worked for a while & now has finally died out. I still get a click from the solenoid but the starter motor doesn't even attempt to operate. Bought a generic heavy duty 12V 100A 4 post relay/solenoid/whatever you call it not to confuse it with the one mounted on the starter and wired that in, but no joy. Starter was weak already and would sometimes grind or turn for a second & stall out.

---------------------

Did you remove both cables from the battery, clean both ends of each cable and the grounding surface?

The next most likely thing is an internally corroded positive cable.

Get a digital multimeter and watch this video: http://www.youtube.com/watch?v=XhRPLgH6uZg

If you need it: Multimeter Tutorial

And: Voltage Drop Testing