Dreaded #2 Fuse blows immediatly in TC40D

[thclimer]

You know the sure sign of madness is you start talking to yourself, but that's precisely what I am doing.:confused2::laughing:

I have to eat some self-induced crow for the statement above in the quote. As often happens, another TBN member sent me a PM because he is having trouble with the start circuits. As I was describing operation of the circuit, and jumping from page-to-page in the schematics, it suddenly hit me that I had been overlooking one significant component that is powered by fuse #2. It's the starter solenoid!!! Wow! Power from fuse #2 goes through the Neutral Sensing Switch on the transmission and then is applied to the Neutral Start Relay. When the relay is energized by the Ignition switch going to Start, power from fuse #2 goes through contacts in the relay and straight to the starter solenoid coil. I had misread the schematic and thought power from the main fuse powers the solenoid, but that is not the case. It is power from fuse #2 that goes to the starter solenoid and that is the source of the surge current that blows fuse #2. Mystery solved! Fuse #2 power does NOT run the starter, that power comes directly from the battery without any fuse, but fuse #2 DOES supply the power that energizes the starter solenoid.

Hey Jim,

Glad you were able to add a little more insight to mysterious fuse #2 blowing issues some of us have had.

Tim

 

[Carykong]

Jinman is The Oracle on the #2 fuse.

 

[SteveInMD]

A starter solenoid draws by far the most current with the plunger all the way out (in the initial resting position). When current is applied from the starting circuit and the plunger moves in, the inductance goes up the current starts to fall. If the solenoid is activated with a weak battery and / or a circuit is a number of somewhat dirty connections the plunger will be thrown in slightly more slowly increasing the duration of the high current draw, which blows the fuse.

The solenoids on these tractors seem to demand full voltage to operate smoothly and crisply. A circuit breaker is better able to handle the occasional less than perfect solenoid plunger throw than a fuse. We've also seen that reducing the number of switches in the starting circuit to one relay switch allows the solenoid to operate reliably and not blow the fuse. (Not promoting one fix vs another here! Just stating what we've learned.)

 

[jinman]

Not only that, Steve, but the starter solenoid has two sets of solenoid coils. One set is pull-in and the other hold-in. When the solenoid fully energizes, the pull-in coil is removed by the mechanical position of the solenoid (It actually puts positive voltage on both leads of the pull-in solenoid so that no current is drawn.). The detailed process is described in the Repair Manual. If the solenoid does not move fully to the energized position, then it stays on high current pull-in mode. Knowing that fuse #2 supplies power to the solenoid explains lots of things including why the rewiring and reconfiguration of the starter circuits also works.

 

[captainsawdust]

Well, I hate to say problem solved without actually finding a definite problem, but I replaced the battery and have had no further issues for the past couple of days.

 

[jinman]

Well, a fresh battery is always good, but if you didn't replace the fuse with a CB, you have just delayed the problem until the next time. It may be a month and it may be a year, but I'd bet it will come back. At least you know exactly what to do if/when it occurs again.

 

[barbqranch]

Jinman's explanation that there are two sets of windings in the starter solenoid might explain why a low battery could cause it to blow the fuse. If the voltage is low and it doesn't pull in far enough to disengage the second starter solenoid winding, then it would pull more current than it would with a full battery.

Also, everything in the circuit drops the voltage some. The fuse or circuit breaker has resistance, they operate on heat. All the wire drops the voltage. If any of the safety switches or wire connectors are a little dirty or tired, that would also drop the voltage.

Also, as a general rule, the higher the current rating of the fuse or circuit breaker, the low its resistance. This is because it takes a certain wattage to heat it enough to trip, and higher current allows the same wattage with less resistance. It is also possible, but I don't know, that the circuit breaker has less resistance than a fuse for the same value.

 

[LetsRoll]

A little story for you guys. Just today while I needed to bush hog. I went out to get the tractor ready. Fired it up and it ran for about a minute and then I heard a pop noise. Well, I knew the tractor was dead cause the dash had no power what so ever. I got my meter out and found the blown fuse (#2) and replaced it and as soon as I tried to start the tractor, the #2 fuse blew again. I ended up blowing five fuses (4 10 amps fuses and 1 15 amp fuse) through the day tracing down the problem. First thing I tested was the ignition switch cause that would be the least hardest to replace. Well, it turned out good. Well, I decided to get down and dirty cause the tractor was having a hard time these past few weeks starting. It was just taking longer to start and the longer time went on, the harder the tractor was getting to fire. The next thing I tested was the glow plug relay cause that relay was on the #2 fuse. Well, it turned out good. Well, the next thing to test was the battery cause it was out in the open and it needed to be checked. Like I said, the tractor was getting harder to start. I thought the battery was low on power, so, I'll check it. Well, it turned out good also. But, the battery ground strap that was bolted to the frame was corroded real bad with rust and dirt. So I clean it and the terminals and then decided to put in a new fuse and try to fire the tractor again. Well, it turned over allot better this time, but the #2 fuse blew again. I knew I was getting somewhere cause of how well it turned over before the fuse blew. Next thing to check was the seat safety switch. Well, I didn't have to check the switch cause about a few years back, I by pasted the switch for several reasons. But, I did find the problem with my jumper wire. It had rubbed on the seat frame and the wire had come into contact with the metal. That was the problem. Turns out, the bad battery ground (lower power from the battery) and the short from my jumper wire rubbing the metal frame of the seat, had burnt the safety controller box that is inside of the dash panel right under the steering wheel. The way I found it (go ahead and laugh cause I am). After fixing the jumper wire for the seat safety switch, I put in a different fuse that I made cause I ran out of 10 and 15 amp fuses. I used an old style round glass tube fuse that was rated for 15 amps. The ones that use the long plastic cover. Its all I had and I had several of them from my hot rod days, so I used them until I could get the right style of fuses. To make a long story short, I tried to fire the tractor again, well, it started right up and I let it run for about 45 seconds and had to turn it off so that I could put the panel back together that is underneath the steering wheel. That panel was off cause I was testing the ignition switch earlier. Here is how I found out that the safety controller box was in bad shape also. Got done and decided to let the tractor run while I cleaned up my tools. Well, the tractor runs for about two minutes and the next thing I know, it shuts off on its own. I look up and there is allot of smoke coming from steering wheel area. I get a wrench and unhook the battery. I knew right then and there, the low battery power (bad ground strap to the frame) and the short from the jumper wire on the safety seat switch had burnt that safety controller box up. I get that box off and I find the housing is cracked from the heat (short) and it had some fluid oozing from it. Well, I clean it up and try to apply 12 volts to it so that I could test it and low and behold, it start smoking again. All well, thinking to myself, that is going to cost me a pretty penny. I call the dealer and that safety controller is going cost me, ready for it....$241 dollars To top this all off, I still don't know if I've found my problem....? I didn't get to test the fuel shut off solenoid yet. I'm just wondering if the fuel shut off solenoid is causing #2 fuse to blow???? My gut is telling me the short from my jumper wire on the seat safety switch is what was causing the #2 fuse to blow? Guess I'll find out when I get the safety controller box. But, my gut is telling me to order the fuel shut off solenoid also......arrrgh. Don't know what to do. Would you guys go ahead and order the fuel shut off solenoid also while I have the dealer on the phone ordering the safety controller box????

 

[jinman]

Would you guys go ahead and order the fuel shut off solenoid also while I have the dealer on the phone ordering the safety controller box????

No, I'd remove the spade connector and unscrew the solenoid. Remove it and test it with 12 vdc outside the tractor. It should be about 12 ohms (spade connector to body) and pull one amp. It's a piece of cake to check.

 

[LetsRoll]

Thanks Jinman, :thumbsup: I've decided to hold off and order the safety controller box from Messick's cause its cheaper than my local dealer. My local dealer wants $241 and I have to go and get it and pay tax which adds up to $270.46. Messick's cost is only $214 plus shipping which will cost about $10 bucks (.30 lbs. which is under a pound = $224). Plus, I don't want to pay for a new fuel shut off solenoid if mine turns out to be good.