Thermistor / solenoid replacement on Jd 4300

[smgchandler]

For years i have put up with the problem of not starting so i replaced the thermistor and solenoid but i can稚 figure something out. Solenoid wont click hard or pull plunger in on start. Clicks hard on shut off great and shuts fuel off. The red black and white wires are connected well and red wire is the only one with juice showing with cheap test light Seems like i have wired something wrong because if solenoid pulled in as hard as it does to shut off engine i would be fine but it doesnt even click. I would like to ask what pulls the plunger in so tractor will start ?? Maybe be dumb question but would the pump in any way push the plunger back so it will start or is it all electric solenoid controlled ? Any suggestions or help is appreciated. I did add a section of maybe too heavy gauge wire to extend thermistor out in front of fuse block to make this easier to get to next time. Could my wire be too heavy ? Or could i have damaged thermistor while soldering to new wire ?

 

[smgchandler]

Plan is to order new thermistor again and solenoid and start new with both and this time use same size wire as on tractor now and put thermistor in wire end similar to factory - i would like to ask if there is a fuse block that could possibly be bad in the fuse box ?? That i could also replace because i am fishing here. I have a fella that wants to buy but i can’t sell if it won’t start ��. Thanks for any suggestions

 

[DanMc77]

Hi SMG:
I have the JD4600 and had a problem with that thermister.

The solenoid has two coils: one for holding and a second one for the intial "pick" where it pulls back out of the way and allows the fuel pump to run, kind of like a start winding in a motor. The thermister provides a little boost to the "start winding" and then when the thermister warms up, it reduces that current. If that "start winding" was energized all of the time, it probably would generate too much heat in the solenoid and it would burn up.

When my thermister failed, and after reading about all of the problems with that part, I removed the thermister entirely and replaced it with a momentary push-button switch. Normally open. Now, before I turn on the key, I press and hold the button. When I turn the key, I hear the satisfying "CLICK" and then I can release the button. I have run my tractor for 2 years like this and it works perfectly. Here's a link where I posted on that.
http://www.tractorbynet.com/forums/...istor-replacement-5.html?highlight=thermister
Look for post #45.

It's also nice because this switch will make it impossible for somebody to start the tractor unless they know they have to push that little switch. So it's a nice security feature.

 

[smgchandler]

Dan i appreciate the information. I am going to check the connections around the fuses or Siemens blocks and replace both parts one more time and if that doesn’t work will try the switch I even have a push button that all i need is a hole to mount. Will post back but it will be the weekend before i get a chance to work on it. Thanks again

 

[jd110]

The power to pull in the plunger has to come through the thermistor. There should be power into the thermistor when the key is turned on and power will flow through thermistor to the pull-in wire at solenoid for about 1second. Then the thermistor will turn it off. A heavier wire will not harm thermistor circuit. Too much heat when soldering could hurt it. I always use crimp type connector to prevent overheating.

 

[smgchandler]

Jd110 i appreciate the information. I will replace the new thermistor tomorrow and use crimp instead of solder I had a feeling that it was a lot of heat I will post back if i got it fixed

 

[larboc]

Next time mine goes I'm going to wire it up to the starter solenoid like the x55 series.

The failure of that $2 thermister inadvertently led to me using too much either and a broken piston and a full engine rebuild for my 4300.

 

[smgchandler]

Wonder why Jd engineers didn’t come up with that on their own ?? Well i have not got around to it yet but maybe if it warms up a little. My plan is to crimp not solder new thermistor in place with a push button bypass just in case thermistor decides to take a crap again. Best of both worlds unless one of you smart fellas suggest something else. Tractor doesn’t have many hours on it at all and i would be sick with a busted piston. Never had to use starting ether. If it will turn over it would start right up even in cold. Thanks for all the post and i will post back with results.

 

[DanMc77]

Next time mine goes I'm going to wire it up to the starter solenoid like the x55 series.

The failure of that $2 thermister inadvertently led to me using too much either and a broken piston and a full engine rebuild for my 4300.

When it comes to using a switch for the "start" winding in that solenoid, it's important to remember that the power to that winding MUST be applied at the same time the power to the other coil is applied. On my tractor with the pushbutton, if I push the button after turning on the key, it does nothing. The solenoid will only pull in if both are energized at the same time when the key is first turned on. So, connecting that start winding to the starter solenoid may not work.

 

[JD755]

The factory wiring on my 755 is a simple connection to the starter solenoid. Very reliable.