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CGK

Blowing 25A fuse

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Hey guys,

New here and looking for some advice from the many gurus here.

Started and ran my 1989 312-8 normally and shut it off without any issues.

A few hours later, went to start her back up and as soon as I turned the key, the 25A fuse instantly popped.

All electrical loads were switched off and there was no indication when I started it that there was any electrical problem.

I replaced the fuse and without sitting on the seat this time, turned the key and the fuse blew again.

I'm thinking short in the ignition switch or some other switch but before I start tearing into it, thought I'd get some ideas

or suggestions here.

All ideas and suggestions would be greatly appreciated.

Thanks much.

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CGK,

 

Welcome to Red Square.  Sorry things aren't going your way at the moment.  Check the 9 pin connector below the battery. those can get corroded and cause trouble. Also, you could try to bypass the neutral safety switch and see if that helps.

 

Others will put in their advice soon as well.

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The wiring behind the ignition switch is cramped into a pretty tight space. With time and vibration the insulation may have worn off one of the wires creating a short. I'd pull the battery and carefully check the wires behind it. Just a thought.....

 

Duff  :thumbs:

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I probably should not start off thinking this engine has 15 amp stator because every time I do - It doesn't - I have bad luck making assumptions on 300 series stuff.

 

but I will make a few assumptions and later tailor some of the troubleshooting if we find this engine has an engine skin mounted 15 amp regulator / rectifier unit.

1/ You have a 3 amp stator charge system (I'm looking at that 25 amp fuse and thinking maybe not?).
2/ The 25 amp fuse does NOT blow when you have the ignition switch in the OFF position.
3/ The 25 amp fuse blows BEFORE you go to the START position on the ignition switch.

First thought is the wiring thru the 25 amp fuse to the ignition switch is OK - because the fuse does NOT blow with the ignition switch in the OFF position. The second item to discuss is the 15 amp fused circuit. Since the 15 amp fuse is NOT blowing, the problem cannot be the circuitry protected by the 15 amp fuse (the 15 amp fuse would blow before the 25 amp fuse - right?).

The diagram below highlites those circuits and eliminates then from view in the 2nd image. We are trying to visually eliminate the circuits that could not possibly be involved in the 25 amp fuse blowing.


25aeliminate15ampcircuit_zpsf517b5ae.gif


25aeliminate1_zps1b8e466a.gif


The second round of eliminations can be the ground wires. Since they are already grounded, becoming grounded thru abrasion anywhere along their length will not change their function.



25aeliminategrounds_zps78c9c9ff.gif



25aeliminategroundsfinal_zps7edfc6fd.gif


Next we can eliminate all the circuits needed by the starter - because the assumption here is the 25a fuse blows BEFORE you turn the ignition key to the START position. Remember, the ignition switch does not apply 12 volts to any part of the start circuity until the operator flips the ignition switch to the START position.


25aeliminatestartcircuit_zps158d420a.gif


See where we are going ?


25aeliminatestartcircuitfinal_zpsb8b89e5


If we make certain the PTO lever is in the off position, the PTO microswitch opens up and therefore eliminates any issues with wiring issues AFTER the switch.


25aeliminateptoswitchcallout_zpsbdbe5deb


Now we are down to just these few circuits.


25aeliminateptocircuit_zps7ac0568d.gif


The following advice is based on a 3 amp stator charge circuit - if you have the 15 amp charge circuit, I'll post alternative troubleshooting later today.

 

Either the wiring to the stator is grounded or the diode in the charge coil of the stator is shorted allowing battery voltage to run thru the stator windings and blow the 25A fuse. If the stator wiring can be unplugged (usually a 2 prong plug somewhere near the engine tins) a shorted charge diode can be eliminated.

If the fuse does not blow with the stator detached, the stator diode or stator windings / wiring are compromised.

If the fuse still blows with the stator detached, wiring harness shorts to ground should be suspected.

The ignition switch COULD be shorted to ground but would require good access to the rear terminals of the switch (or removal from the dash) to do resistance checks.

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WOW "Save Old Iron" you have given me all the ammo I think I need to drill down into this problem!!

What a great post !!

Thanks a million and I'll post up the results of my diagnosis when I'm done.

 

I'm so glad I joined Red Square, this place rocks!!

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CGK,

 

I was going to ask you to do this earlier but forgot.

 

Check the 15 amp fuse also - see if its intact or blown also - just curious.

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Mystery half solved. I tore into the problem and found three wires from the igintion switch that were worn through the insulation and finally shorted to the chassis causing the 25A fuse to blow as soon as the key was turned to the on position.

So, since I had everything apart I decided to replace the starter solenoid, starter switch, and seat switch. Hooked everything up, connected battery and here's what happens:

 

Iginition turned to on position: Power to all electrical loads. 25A fuse is good, 15A fuse is good, front and rear running lights good, seat switch LED on, hour meter running.

I also tested the LED panel with the test switch and all LED's are fine.

 

I then attempted to start with not success. Clutch depressed, PTO off, turning key to start causes seat switch to go off and nothing else happens. No relay clicking or starter action at all. It's like the battery is not even connected. Battery is fully charged as well.

 

Any ideas or clues here that might help diagnose the problem??

All suggestions gratefully accepted.

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I failed to mention that with the key on and sitting on the seat, the seat LED stays on. I can't remember if it is supposed to stay on until key is turned to start or not.

Could something else have fried when the short took place? I wouln't think so since the 25A fuse should have protected the circuit but who knows.

Any thoughts on that angle?

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CGK,

 

The seat switch idiot light should not be on when the key is in the "Run" position, and someone is in the seat. Try bypassing that switch and see what happens.

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Remember the seat switch will not be a factor in CRANKING the engine, the engine will turn over with the operator in out of the seat.<br /><br />Where the seat switch comes into play is when the PTO is engaged and the operator leaves the seat, the engine will be forced to shut off. The shut off is handled by the IGNITION circuit not the CRANKING circuit.<br /><br />The clip from the demystification guide shown below will guide you thru all the switches that come into play for getting the relays to "click" and engine to crank.<br /><br /><br /><img data-cke-saved-src="http://i1228.photobucket.com/albums/ee458/SOI_University/RS Assist/312-8 25a fuse blow/25anocrank_zpsb768818a.gif" src="http://i1228.photobucket.com/albums/ee458/SOI_University/RS Assist/312-8 25a fuse blow/25anocrank_zpsb768818a.gif" /><br /><br /><br />

(formatting errors reported to admin)

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25anocrank_zpsb768818a.gif

You did say a few wires off the back of the ignition switch were shorted to sheet metal. Is it possible the Tan wire was not hooked back to the I terminal of the ignition switch ? or possibly the Tan wire is damaged and not applying power to the oil safety switch and then onto the safety relay?

Do you have a meter or testlight to check for the presence of voltage at the safety relay terminal?

Once the safety relay gets powered up , the PTO switch contacts and the Clutch switch can then deliver 12 volts thru the safety relay to the starter relay to power up the starter (and then crank the engine).

Chuck

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Thanks a bunch Chuck for all your help and tips. You're an encyclopedia of Horsey knowledge.

I do have a meter and will check for voltage at the relay terminal, which by the way I also replaced the original relay as well. I'm digging into my stash of factory and NOS parts that I accumulated over the past 15 years or so.

I did clean and resplice all the wires that were suspect at the ignition switch but I guess I'll have to check them all. One thing I did notice was that all of the female connectors were pretty gunked up with dirt and grime from 23 years of use. Would you suggest that I entertain the thought of replacing all of the connectors as well or just try to clean them as best as I can and see if that works ?

I'll poke around some more to see if I can discover the problem here and will update results.

 

Thanks again

Chuck K.

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Thanks a bunch Chuck for all your help and tips. You're an encyclopedia of Horsey knowledge.

Not so much "Horsey" knowledge as 40+ years in electromechanical work that translates very well into troubleshooting electrical and mechanical "Horsey" issues.

 

I don't have a good picture of the safety relay in my image database (hint, hint) but I imagine the case (if metal) will be the ground and (hopefully) the a dark blue wire to one of the terminals will be the trigger for the relay. Trace the power from the I terminal on the ign switch thru the oil level sensor to the trigger of the safety relay. The safety relay should click as soon as the ign switch goes to the START position. If the starter relay doesn't engage, that's another issue. Let's get the safety relay engaging then see what we have.

As far as cleaning the connectors, grease and oil and dirt can all be washed away quite nicely with brake cleaner spray. Oxidation of the terminals is easy to address on male fittings but no so easy on the females. All of the deox cleaners that worked well back in the 70's and 80's are now all off the market. The Blue Shower products from the 80's worked great. I figured they would because even in the 80's they had a skull and crossbones logo on the label!

 

If you try to chop off the female connector and use the wire length left, the copper wire is sometimes corroded and even a new crimped terminal doesn't give a good connection thru the oxidation of 20 -30 + years. In that case, replacement of the entire length of wire is usually the only permanent cure.

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Frustration Update:

I rewired all connectors to the starter switch and reinstalled. I rewired the seat switch connectors and reinstalled. Checked for power going to the oil sensor with the key in the "ON/RUN" position. Getting power going to the sensor. All other conditions remain the same:

seat switch LED lit with unoccupied seat. Hourmeter running, Ammeter showing fully charged battery.

 

Turning the key to start causes seatswitch light to go out with unoccupied or occupied seat, power to the oil sensor switches off and still no activity on the safety relay and consequently, no start.

I have tested and confirmed that the starter itself is good so that eliminates that from the equation.

 

What still has me bumfuzzled is the fact that the only LED that operates during the switch on, start, and off cycles is the seat switch LED. Ignition switch ON - LED lit. Ignition switch to START- LED off. Both conditions occur whether the seat is occupied or not.  No other LEDS light up whether or not the PTO is engaged or not or whether the clutch is engaged or not. Shouldn't either or both of those LED's light up during the start cycle if they are engaged??

 

Everything I am seeing keeps pointing to a wiring issue involving the seat switch but I don't know where else or what else is causing this no start condition. What else should I be checking for or have I missed something?

What I thought would be a seemingly easy fix is quickly turning into an electrical nightmare all due to a couple wires shorting and blowing a fuse.

If I can't get this figured out, I may blow a fuse soon. :)

 

As a  last ditch option, is it possible to wire the start/run cycle and bypass all of the switches that prevent it from happening?

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I hear you about your concern on the seat switch. If you would like to start troubleshooting the seat switch and abandon the safety relay troubleshooting, I'll be glad to follow along. But First, let's do a quick starter check first to make sure we don't get snafu'd by a starter issue.

No one here will openly advocate "bypassing" the safety switches, but there are ways of troubleshooting the start circuit with jumper wires.

Best to start you off by reading the still active thread at this link



Pay particular attention to the number of terminals you have on your STARTER RELAY (not safety relay). Check to make sure you have the transmission in neutral and brake engaged. Jump the two large main terminals on the STARTER relay and the engine should start cranking immediately.


2bfa7a57.gif


or


nocrankrelayjumpmain_zpsf53f795d.gif


You can disregard the ammeter I have pictured in the jumper wire, I insert an ammeter to tell how much current the starter is drawing - kind of a two'fer to check starter condition too.

Remove the jumper. If the engine does not crank, we either have a wiring problem to the starter relay or a questionable starter.

If the engine does crank, leave the jumper on the large starter relay stud that secures the wiring from the battery (+) terminal. If your starter relay only has 3 terminals, connect the open end of the jumper to the small "trigger" terminal on the STARTER relay.


1b45344c.gif


The STARTER relay should engage and the engine should crank.

If you have a 4 terminal STARTER relay, one of the smaller terminals must be connected to a chassis ground. The second small terminal will be the solenoid "trigger". Make sure the "3rd terminal" ground connection is secure and clean.

Retest the starter function again as outlined above - STARTER relay (+) to the STARTER relay trigger terminal.

Let's make this quick test and see what the results are. All we are looking for is the engine to crank over at this point.

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OK Chuck,

Here's what happens:

I have a four terminal starter relay (solenoid) that is new. Jumper between two main posts fires up the starter and turns the engine over.

Moving open end of jumper from +BAT post to relay trigger terminal does nothing. Ground to relay terminal is still connected.

 

I would have thought that hitting the trigger terminal direct from the battery would energize the starter, no?

 

Next step ..........................?

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OK Chuck,

Here's what happens:

I have a four terminal starter relay (solenoid) that is new. Jumper between two main posts fires up the starter and turns the engine over.

Moving open end of jumper from +BAT post to relay trigger terminal does nothing. Ground to relay terminal is still connected.

 

I would have thought that hitting the trigger terminal direct from the battery would energize the starter, no?

 

Next step ..........................?

Moving open end jumper from bat to relay trigger does not sound quite like SOI's picture.. you want to leave the battery and the starter connected to their respective posts, and apply voltage to the trigger terminal. so you want a jumper between battery and trigger.  If you apply voltage to the trigger without being able to draw from the battery, the starter will not go, as the trigger post just moves the plate and closes the connection between the two main studs.

 

Dunno if this is the same, but I get starting gremlins with my 414, and they are nearly always related to ground issues. Check the ground on the solenoid.. I also get weirdness because the ground strap from the battery is run to a bolt on the tower that is secured through a clip, and can sometimes vibrate loose and give poor contact.

 

There is only one time I did have a bad solenoid, and SOI told me how to fix it (although I was too lazy and just bought another.)

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What we know so far.

 

Battery is good as evidenced by the starter turning over when the starter relay main terminals are jumped.

Wiring to starter relay is good.

Starter is grounded to engine properly and engine is properly grounded to chassis.

 

Let's recap a 4 terminal relay troubleshooting setup.

 

 

testing4terminalstarterrelay_zps3fb7df7d

 

 

We know we have 12 volts at the Battery (+) terminal on the large lug of the relay.

You have already jumpered the Battery (+) terminal of the starter relay to the smaller trigger terminal of the relay (green wire in image above). If the jumper wire is OK , then the 12 volts from the battery is applied to the trigger of the starter relay. This should energize the starter relay (and energize the starter).

 

One step left. Jumper the 4th starter relay terminal (black wire in the diagram above) to a good chassis ground or to the (-) terminal DIRECTLY AT THE BATTERY .

 

If the relay doesn't click in and start the engine cranking, then we may have a defective STARTER RELAY.

 

I did put together a checkout routine for starter relays a while back. Let me see if I can find that link and post it here.

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Here you go,

 

a routine to check out 3 or 4 terminal starter relay using a multimeter and a battery charger.

 

One of my earlier works that I need to update to current SOI U visual standards.

 

 

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Hey guys,

Got all your responses. Thanks a million.

SOI- love the "schematics" extremely helpful !!!

Now all I have to do is print this off and step out the procedures and see what happens. As I mentioned before, I did install a new 4 terminal starter relay, rewired the new starter switch and installed a new safety relay and seat switch.

Still getting the "no start condition" with the key and seat switch LED on when the key is turned on.

 

So I'll noodle through the test procedures you so graciously provided and post up the results when done.

Woodchuck, I like the idea of grounding to an engine mounting bolt. I'll definitely do that once I find out what's wrong here.

Thanks to all !

Chuck

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I'm Back ! Was out of town all last week and when I returned home, I spent this past weekend scouring through all the notes from SOI and others and traced, retraced, checked and rechecked every wire, connection, ground and switch. I practically rebuilt the entire wiring harness. It's amazing how 24 years of flawless running can cease instantly due to bad connections, grounds, and switches. I found some bad wires, connections and weak grounds.

So, I replaced the original ignition switch, original seat switch, original solenoid and safety relay. Rewired the iginition switch connection and replaced every ground connection from the battery through to the ignition switch. I used heavier 14 guage copper wire to run all of the grounds and grounded directly to the frame or engine wherever I could. Sealed all the connections with Plasti Dip to prevent moisture and corrosion.

Put it all back together and VOILA !!! the old girl cranked right over better than new and she purrs like a kitten!! After 1627 hours, she's ready for another 20 years of service, at least !!

 

Thanks to all who contributed ideas and tips and a big "hats off" to SOI for all of the detailed illustrations and instructions. They made my investigation and ultimate solution a whole lot easier to get through.

 

You guys rock !!

Thanks,

Chuck

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CGK,

 

Great news. The Wheel Horse tractors for the most part are fairly simple machines. That is part of why they last so long. They were well built in the first place and with proper care and maintanance will last as long as we want them to.

 

I was speaking to another Wheel Horse guy recently and he used the term "Lifetime Tractor" in reference to the Wheel Horses, as opposed to something you buy at a Big Box store and discard after a few seasons.

 

I like the sound of "Lifetime Tractor" better. Long live your 312!

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