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I have a John Deere 318 I have replaced the starter, ring gear, ignition switch and battery now it seems that I'm only getting 5-7 volts to the starter from the ignition switch. Sometimes it turns over and sometimes it just clicks like the battery is low. All other posts on the switch get 12 volts when you turn the key except the post with the wire in the harness that goes directly to the starter. I've tested the Battery it is at 12.5 volts
 

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Trevor, Here's the wiring for the starting system from TM1590:
267153

Depending on your serial number, see X8 above, you may or may not have a brake switch. You've probably got dirty connections someplace causing the voltage drop. Check each component to determine where you're losing voltage. Bob
 

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I agree with bob, probably a connection somewhere. Was new starter painted? Depends on engine and housing of starter for a ground. All surfaces need to be clean and unpainted to make a good connection.
 

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Trevor. go on Ebay or Amazon and search for "john Deere 318 starter improvement kit" Maybe this link will work.

JOHN DEERE Onan Oem 318 420 Starter Improvement Relay Kit, Harness Am 106304 | eBay

Yours is a common problem with 318's and many other JD tractors. As they age, the resistance in the safety circuit switches start to deteriorate causing low voltages at the starter. The solenoid then cannot pull the relay in hard enough to make good contact. It just clicks!
 

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Joe, I agree with the starter improvement kit, but not sure if it will help in this case. Would 5-7 volts pull in the contacts in the starter improvement relay? I believe these are to get proper amperage to the solenoid and need proper voltage to operate. Bob
 

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Bob, this is exactly what happens with 318's. Look at the diagram you supplied. In order to pull in that big relay coil on the starter the current has to pass thru all of the safety's, the key switch, fuse holders, circuit breaker and all the connections and bad wires associated with them. And with this type of starter the solenoid first pulls in the starter gear to the flywheel, then forces a large contact to complete the circuit from the battery to the starter motor.

Over time the resistance in this circuit continues to build. It is the resistance that is the issue. (bad switches and connections) With resistance comes voltage drop and increased amperage flow. (Short circuit at the weakest connection and lots of heat to come with it) Amperage is a measurement of current flow in a circuit. Voltage is a measurement of pressure. And amperage is the result of voltage and resistance. (Ohms law) High resistance produces lower voltage at the end of the circuit.

You can equate electricity and especially direct current with your garden hose. The wire would be the hose. Voltage would be the pressure the water system is operating at. Amperage would be the amount of water flowing thru the hose. But the amount of water flowing (amps) is dependent on the resistant. (Nozzle on the hose) With a controlled restriction the pressure (voltage) stays relatively the same. But if you put a bunch of kinks in the hose, (high resistance connections and switches) pressure (voltage) drops with each one. And soon you don't have enough water (current) to wet your hub caps. (pull in the starter relay)

The starter improvement kit installs a separate relay near the starter to eliminate all of those devices and connections and allows a direct circuit connection from the battery (not really but close) to the relay. But it still maintains all of the safeties That circuit (usually the purple wires) now only has to pull in a very small relay coil rather than that big one mounted on the starter. It is really a work around to solve the problem but would have been the proper way for Deere to wire it from the beginning.

I would guess that Trevor is reading the 5 -7 volts with all the connections made. I would also guess if he would remove the wire from the solenoid he would see 12 volts at that point. (Refer to my explanation above, even with the kinked hose the water pressure returns)

You're correct but keep in mind that large coil solenoid is part of that circuit and is the largest producer of resistance. I'm also sure that if Trevor held the start switch on continuously he would soon find the main culprit as it would become very hot.

The real fix is to replace all the worn out switches, connections and if necessary the wires. But include the improvement kit. Thirty bucks is a good investment in any case. But most of us don't want to do that so that's where the improvement kit alone comes in. I tried to keep it short. But?
 
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Joe, I agree 100% with all of your statement. However! I'm thinking with the wire off of the solenoid, he'd still only get 5-7 volts and I don't know if this will pull in the starter improvement relay.

I fully understand you hose concept....good example by the way! I'll assume the 'kinks are still in the hose/wire' and these are limiting the amount of volts & amps available to the starter solenoid. Well, 'kinks' are dropping voltage and amperage will be whatever the largest fuse/fusible link is rated for.

I may very well be wrong in my thinking here, but I'm thinking if you have 1 millivolt due to resistance (or kinks!) and you disconnect a wire and go straight to ground, you're gonna blow a fuse...assuming let's say the source/battery has a 200 amp capacity and the largest fuse in the system is 25 amps! I'm thinking fuses are rated for amps and not volts...or the combination, watts. That's why you can use a fuse rated for 600 volts in a 250 volt circuit and still have the correct amperage protection. Correct??????? NOT challenging, asking! Bob
 

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Joe, I agree 100% with all of your statement. However! I'm thinking with the wire off of the solenoid, he'd still only get 5-7 volts and I don't know if this will pull in the starter improvement relay.

I fully understand you hose concept....good example by the way! I'll assume the 'kinks are still in the hose/wire' and these are limiting the amount of volts & amps available to the starter solenoid. Well, 'kinks' are dropping voltage and amperage will be whatever the largest fuse/fusible link is rated for.

I may very well be wrong in my thinking here, but I'm thinking if you have 1 millivolt due to resistance (or kinks!) and you disconnect a wire and go straight to ground, you're gonna blow a fuse...assuming let's say the source/battery has a 200 amp capacity and the largest fuse in the system is 25 amps! I'm thinking fuses are rated for amps and not volts...or the combination, watts. That's why you can use a fuse rated for 600 volts in a 250 volt circuit and still have the correct amperage protection. Correct??????? NOT challenging, asking! Bob
Bob, wow! This could go on for a long time. :)

"However! I'm thinking with the wire off of the solenoid, he'd still only get 5-7 volts and I don't know if this will pull in the starter improvement relay."

You would not see that 5 - 7 volts at the new relay as it's source is not connected to the circuit he's measuring. That new relay would see the full 12 volts as its source is the large battery cable. The coil on the new relay is much smaller and would pull much less current than the starter mounted coil. Hence, no voltage drop. At least not as much.

Trevor: You can stop reading here. If you chose...

Fuses are "current limiters" not voltage limiters. Voltage is controlled by the source. (Potential in electronic terms) In this case the battery. Current flow (amps) is controlled by the resistance in the circuit. As long as there is some resistance in a circuit, it is not short circuited until it exceeds the capacity of the wire or fuse. The fuse or breaker is installed to protect the wires and their capability of carrying current, not to protect devices in the circuit. So, if for example, you had a thirty amp fuse in front of a very small 22 ga wire, the fuse would not blow when touched to ground. The small wire would burn off. Same with switches or terminals with bad contacts. That's why switches can burn up and not blow a fuse. And it also demonstrates that fuses do not protect devices.

Without a fuse in the circuit the wire itself becomes the fuse or current limiter. The fuse will not blow unless the total current flow, which is controlled by resistance has exceeded its rating. Too much resistance after that fuse and you get excessive voltage drop. (Trevor's problem) You do not measure resistance in "Millivolts". Millivolts measures the result of resistance. (voltage drop) and there is no mention of it in Ohm's Law. You measure resistance in Ohms. A short circuit is one with no resistance at all but that is virtually an impossibility as there is no such thing as infinity. (The little symbol on your multimeter)

One millivolt is one thousand of a volt. So to use that measurement in Trevor's case you would have to measure the entire circuit in the state he is testing it. If the battery was currently at 12 volts and he is seeing 7 volts, there would be a 5,000 millivolt drop across the entire circuit. Not an easy to digest number. That's why it is used (usually) across single connections or terminals.

Even touching your wire to ground has some resistance but not enough to control the flow of electrons thru whatever wire size your doing the touching with or the fuse in that circuit. Hence a short (closed) circuit! Or at least one that exceeds the fuse or wire rating. And lots of heat is produced. That's how a welder works. Basically a controlled short circuit controlled by the cable size and the electrode size. The electrode becoming an consumable fuse so to speak. The welder itself controls the amp flow by using various sized resistors and thus controlling the heat (current flow) at the stick. In your example, install any load on that wire before you touch it and it will not short circuit. (Like a bulb or tester) The resistance of the bulb is controlling the current flow.

As for "Ampacity" of a battery? That has little to do with Trevor's problem. That is a calculated measurement of a batteries potential current delivery over a period of time. In any battery, those little electrons want so badly to go from negative to positive they will jump at any chance to do so. A twelve volt drill battery would behave in the exact same way. If you were to connect a large enough link across the battery terminals, it would simply drain the battery very quickly. Again, assuming the battery is capable of doing that.

Google "Ohms Law" and read up on it. It's very simple. But it is law!

Now that we nauseated poor Trevor to death! Or, anybody else that's made it this far, maybe we should discuss this stuff over lunch again. Or at least a PM. But I'll leave it here. Who knows? It may be helpful to somebody. Or, I may be completely FOS! :)

Joe
 
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Joe, you are not FOS, let's just clear that up right now! You go to great lengths to explain yourself, I suspect that you are proficient at typing, I wish I was but I am not. I have been involved in electronics my entire life so I understand you, other people maybe not so much. Tom
 

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Joe, you are not FOS, let's just clear that up right now! You go to great lengths to explain yourself, I suspect that you are proficient at typing, I wish I was but I am not. I have been involved in electronics my entire life so I understand you, other people maybe not so much. Tom
Tom, thanks for the kind words. Just trying to put some humor in a dull subject. Yes, I consider my typing abilities to be one of the most useful skills I've acquired. Back in high school I was the subject of ridicule as I was the only male in the class. In later life it went a long way in work place to make life much easier. Rather than pencil out a memo or letter for the secretary to type, I did it myself and she simply proof read it and formatted it properly and sent it along. She loved me for it! (My lousy handwriting may have had a lot to do with that. Or vice versa) Many times I'd find other managers sneaking up to watch me go at it especially if they were involved. But to this day a habit I acquired in high school still plagues me. I constantly type "teh" in place of "the"! Bugs the hell out of me!

I wish schools would once again teach these skills along with basic shop and mechanical classes. Again, back then it was compulsory in junior high as introductions to different trades. Electricity, plumbing, welding, machine shop, auto shop, printing, and others. What it really taught was curiosity, problem solving and self confidence.

Thanks again Tom.

Joe
 

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Let me continue for just a bit. I'm thinking both you & Tom are interested!
I FULLY understand & agree with MOST everything you said and I'm totally familiar with Om's Law. What I disagree on is that the improvement relay doesn't see the 5-7 volts. The contacts do not, I agree, as they are connect to the battery and the solenoid terminal. The coil to operate these contacts WILL see whatever voltage comes through the purple wire...in this case 5-7 volts... as this energizes the coil and closes the NO contacts between battery & solenoid.

To get back to Trevor's issue, I think he needs to check each switch & connection as shown in the diagram in post #2 to determine WHERE he's losing voltage. It may be 1 or 12 places, he may need to replace a switch...or 3... or maybe just clean up 1 dirty connection.

Trevor, Start disconnecting one plug at a time. Start with ignition switch or, more easily identified, the 20 amp fuse. Remove fuse, turn key "On" and probe terminals with meter lead. You should get battery voltage. Follow wiring and switches and check voltage all the way to the purple wire. To clean the female connection, it's best to remove wire from plug. If you're not familiar with how this is done, give us a yell! Keep us posted as to what you've done and results. Bob
 

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Trevor,

In your initial posting #1 you said that "All other posts on the (ignition) switch get 12 volts when you turn the key except the post with the wire in the harness that goes directly to the starter." That one contact is measuring 5 to 7 volts as indicated in your comment. We presume that you measured this at the full key rotation to the START position, which is where that purple wire on the key switch terminal S1 gets activated. Your statements lead us to understand that key switch terminal S2 does have a solid 12 volts, and if that is the case all the safety switches in the diagram Bob gave in post #2 are working correctly. This would indicate the key switch itself is most likely your root cause, and is very common for machines of this age where the key switch internal contacts get worn and corroded over time. If the machine is stored outside in the weather much during its history, water will find egress through the key slot and other means to make this failure even more likely. Many members here routinely replace the key switch on a recently acquired tractor of unknown history as matter of preventative maintenance. These key switches are not very expensive and easily installed, so give it a try and report back. We don't normally suggest just "throwing parts" at a problem, but your measurements show that this area is the reason you are getting unreliable starting performance.

Chuck
 

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First off. I don't think Trevor is paying attention to any of this. I can't find any response so far. But,

I certainly agree with repairing the root cause. But as Chuck touched upon throwing parts at the problem can get to be expensive. And frustrating. Hopefully he didn't change the starter, ring gear, battery and key switch due to this problem! That whole statement sound fishy to me. In reality each and every one of the switches, contacts, terminals and the starter solenoid itself are all potential separate sources of this problem. And even if the complete wiring harness and components were replaced with new, it would still be a poorly designed system. The best thing going for it is it is very basic and the quality of parts were much better thirty years ago. If the key switch were to be replaced (WHICH IT WAS SAID TO BE) again and not solve the problem I can see endless back and forth posts moving from one switch to another and terminal to terminal until some lucky contributor took the prize for solving it.

As others, I made an assumption. There "seems to be only" 5 to 7 volts? Seems? Not a real positive measurement to say the least. How he measured it and what tool did he use? Was the reading taken with the wire connected or removed? Was it taken with a good ground or touched on a rusty muffler? There is no wire that goes "directly to the starter" unless the wiring was completely altered. And, if the only terminal on the switch with low voltage is that of the starter, why is he asking the question? The answer would be obvious. His new switch was faulty. I didn't and don't put a lot of thought into those numbers without knowing how he arrived at them so I don't get all hung up on them? Ignoring his "data", my assumption was simply his problem was the same as so many others. And therefor suggested he start where so many others went. There is a reason so many of these kits are sold. Not only in 318's but many other engines using the type of starter solenoid combination. And yes, he should probably change the switch. Again! Just to be sure! Chuck, I'll give you that.

Bob, without giving a lick about the 5 - 7 volts thing, it was my intention when I first responded to inform Trevor of a known improvement that to the best of my knowledge usually eliminates the problem. It has worked every time I used it and it makes perfect sense design wise. If against my better judgement I purchase a 318 its the first thing I install. But I make my own rather than buy it. That little relay requires far less current to energize than the large starter mounted solenoid thereby greatly reducing the load on those deteriorated safety circuit connections. Less load, less voltage drop. Done discussing that. I, unlike you took the 5 - 7 volts with a large dose of salt. The cost of the kit is around thirty bucks and even if it didn't solve the problem it is a good investment. The system will work much better when connected in this fashion.

Believe it or not, I prefer to cut to the chase, and not get into these long theory and step by step diagnostic discussions. But I can't seem to help myself sometimes. (Actually, quite often) Bob, all I can say is if Trevor is reading any of this, which I doubt, we sure sent his mind spinning with all of this technobabble! :)
 

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You can make your own starter assist relay assy for around $5 (or less if you have a junk box). Meanwhile, the 7 volts should be enough to activate the relay, which in turn will throw battery voltage into the solenoid, which will throw battery voltage into the starter. BUT, it would not hurt to get a can of spray contact cleaner and spray off all the connections in the safety circuit. Also, clean the connection where the battery ground cable attaches to the frame.

A schematic can be easily found for the assy, or PM me and I'll send you one.

Interesting discussion by some knowledgeable folks in this thread.
 

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You can make your own starter assist relay assy for around $5 (or less if you have a junk box). Meanwhile, the 7 volts should be enough to activate the relay, which in turn will throw battery voltage into the solenoid, which will throw battery voltage into the starter. BUT, it would not hurt to get a can of spray contact cleaner and spray off all the connections in the safety circuit. Also, clean the connection where the battery ground cable attaches to the frame.

A schematic can be easily found for the assy, or PM me and I'll send you one.

Interesting discussion by some knowledgeable folks in this thread.
Good video. It's a lot easier to understand watching it done. Very hard to explain in writing. As mentioned above, I also make my own relay assist. If I'm rewiring the tractor (or whatever) I incorporate it right in the new harness.

Thanks for posting it.
 
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I am also a proponent for making your own -- it certainly is not expensive to do so. Surplus Center has these cube relays and sockets for under $5, and local supply houses and auto stores also have similar relays.


Chuck
 

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I am also a proponent for making your own -- it certainly is not expensive to do so. Surplus Center has these cube relays and sockets for under $5, and local supply houses and auto stores also have similar relays.


Chuck
These are really handy gadgets to have around. I use them for many different things. I always use them when installing a magneto type engine where the machine was originally a point and coil ignition. Its the easiest way I know of. Purple to energize the coil, white kill wire thru the NC side of the relay then to ground. Done deal. I have several in my F150 but that's for another blog site.
 
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These are really handy gadgets to have around. I use them for many different things. I always use them when installing a magneto type engine where the machine was originally a point and coil ignition. Its the easiest way I know of. Purple to energize the coil, white kill wire thru the NC side of the relay then to ground. Done deal. I have several in my F150 but that's for another blog site.
I'm new on this site, tho I frequent others. It would be interesting to see how others use the relays to their advantage. Uses are likely endless but have not really given it a great deal of thought. The purpose you mention above is thought provoking!
 
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