40 amp fuse ("fusible link?) keeps blowing

[Bruce Fehring]

I have a ZD18 mower and have gone through three 40 amp fuses (large green one located near starter) in the past few days. It tends to blow while starting the machine after having it has been turned off for a while.

Of course, the fact that it is blowing is indicative of the fact that there is a problem somewhere...a short, a bad switch, ???

Can someone please suggest the best troubleshooting procedure for this problem?

Many Thanks.

 

[Ob1kubota]

Hey Bruce look at the L2800 post and if this doesn't work, I will look at my wiring schematic ASAP and see what all is going on with the 40 AMP start circuit. Won't be tonight because both the ZD326 & ZD21 will be mowing my cowless pastures....

 

[Bruce Fehring]

Thanks for the input. My gut is telling me that the problem lies in the solenoid only because the issue arose after a major overheating event and the solenoid and starter sit right next to all that heat. However, it may also just co-incidentally be in the starter switch.

I do have an Metex M-3860M multimeter tester, but have never used it much. The instruction manual is so technical that I am lost. If I want to check continuity in the solenoid, do I put it on the "V~" (volts) setting and check for 12 volts through the solenoid? Or ????

Same test for the starter switch?

 

[cabu]

Hello Bruce,

I just checked a picture of your multimeter.
If you want to check continuity you need to turn the Metex to the middel white position (Resistor and continuity beep). You will see the resistance and maybe also hear a beep, if you have a very low resistance. Maybe you have to switch on the beep with the button with a beep symbol.
Or you can do it the way you suggested, check the voltage at the battery and if possible between the Selonoide and the starter. Both times when you are starting. There should be only a small difference in the values.

But if you are telling, that the fuse blows after the engine was turned off for a while, I suggest, that the cold engine forces the starter to much now after your problems with overheating. Maybe problems with a bearing. Does the engine has the same power as before? Is the engine easy to turn, if you remove the glow-pluges?
If so, maybe then your starter has overheatet and the coil's are damaged inside. So when you start and need a high current because of the cold engine maybe a wire of a coil get to hot, expand and touch the case or another wire, causing a very high current -> and blow the fuse.

Hope that helps a little bit.

Carl

 

[Ob1kubota]

Thanks for the input. My gut is telling me that the problem lies in the solenoid only because the issue arose after a major overheating event and the solenoid and starter sit right next to all that heat. However, it may also just co-incidentally be in the starter switch.

I do have an Metex M-3860M multimeter tester, but have never used it much. The instruction manual is so technical that I am lost. If I want to check continuity in the solenoid, do I put it on the "V~" (volts) setting and check for 12 volts through the solenoid? Or ????

Same test for the starter switch?

Okay I'm back Bruce with the Diagrams you need for troubleshooting, cowless pastures mowed, you may be spot on with a dragging starter because the 40 amp fuse is a heavy duty slow blow. It is in series directly with the #30 pole on the ignition switch and heavy gauge wire terminating at the battery starter field winding and loops on to the positive battery pole itself. Bench test the starter by placing a push button remote switch between the starter solenoid Pin ( Black W/purple trace) at the starter and the heavy field/battery (red wire from the battery itself.) Now here's the trick, place a DC clamp on Ampmeter over one of the remote switch leads, push and hold in the button on the remote switch while reading the Amps on the meter. If it's greater than 50 amps for 15 seconds it will blow the 40 Amp fuse and you have found you have a starter near lock rotor. ( needs rebuilt or replaced to stop the overcurrent draw from the battery circuit) you can do this

 

[joekimtkd]

Easiest way to find out trouble spot is continuous test.

First of all, disconnect the Positive (+) connector from the battery.
and start from Positive (+) connector and the frame with continuous test.
(make sure you don't put 12 volts into your tester. it will fry your tester or fuse.)
and alternator, starter, solenoid, check all wires, regulator...etc.
once you find where the leakage is, disconnect the connector and
start narrow down where the leakage is... and you will find trouble spot in no time.

Good luck.

Joe.