First of all, it's with the blessing of the moderators that are assigned to this section that I am posting and sticking this thread.
I have a John Deere STX38 that has been plagued with the starting problem that seems to be inherent to that machine. You turn the key, and you get the good old "click" from the solenoid. A small smack on the starter with a nearby tool (screwdriver handle, hammer, spade, etc.) would generally make the starter engage and turn over. I tore the starter apart several times, cleaning, lubing, etc. trying to find/fix the problem, to no avail. Then, somewhere, I read a post about the availability of a "Starter Assist Relay" that was sold by John Deere to fix this problem. Price was somewhere in the neighborhood of $25. Well, that was a bit steep for me so I went about searching for a less expensive alternative. I found a post on another forum telling of fabricating a similar item for Volkswagon automobiles with the same issue. I decided to try and build my own. Subsequent to my original post in the John Deere section, others have approached me for a copy of my schematic for different models of John Deere and different brands of machines. The cause of this situation is that over time the different safety relays get corroded, connections get corroded, batteries are still good but put out less than optimal voltage. This alteration does not in any way bypass any of the safety switches on your machine.
If you could not start your tractor because of a safety issue prior to installation of this relay, you still will not be able to start it.
Well, the first thing in this project that I needed was a relay. Plain, old relay. The kind that every auto on the road has 6 or 8 of. I went to a name brand auto parts store, with the design of the relay drawn out on a sticky note, so I could tell them what I needed. When I walked in and told them what I was looking for, so I could build a project for my lawn mower, I got the old "Deer (not Deere) in the headlights look".
"I don't think we carry lawnmower parts like that."
No, I said, I need an auto relay, it's for a project I am building for my lawnmower.
"Here's all our lawnmower parts. See, we just carry spark plugs."
No, let's start over. Do you sell auto relays, like for horns, lights, fog lamps, etc?
"What kind of vehicle?"
It doesn't matter!
"Well, we sell trailer light kits for about $25 over here."
We go over there and he shows me the light kits. Right next to it was a relay just like what I wanted for $3.95ish. I'll take this. It's just what I need.
"Do you think that will work in a lawnmower?"
Anyway, I take my purchase home and begin my assembly. First thing I notice is my shortage of different colors of wire. I thought about going back to the auto store, but I am pretty sure they didn't sell "Lawnmower wire" there, so I compromised. I cut 4 lengths of wire about a foot long each. Put some female spade connectors on 1 end of each wire, attached them to the relay. Then, I read my directions and compared them to the info on the back of the relay package and figured out my next step. I labeled all the wires (ground, 12v, key, solenoid) and started my installation.
I don't know about you, but whenever I work on something and it's time to give it the old "college try", I am a bit nervous about the outcome. I always dread that my work was for naught, and when I prepare to see if I made any difference in my machines operation I always fear the worst. Well, I plop myself right down on the seat, make sure that the PTO switch is off--check, in neutral--check, turn the key--NOTHING. Oh, I forgot to re-attach the battery. Fixed that, let's try it again. Sweaty hand reaches down to the key turn it to the "START" position, and bingo! Turns right over! Oh, well, that had to be a fluke. It was just luck. Gotta try it again, just to be safe. Sure enough, turn the key and away she goes. Oh, boy. I gotta get some pictures of this and post 'em on MTF. This is really gonna be a hit! And, it appears, it was a hit. I have had many requests for this schematic since the original post and about everyone reported a success after installation except 1 fellow, and I think that he did figure out the problem. So, here is the schematic for the starter relay, along with a link to my original post, in case you have any questions. If you click on the relay, you'll get a larger image that you can print out. If you have any problems or need further info, just PM me or drop an e-mail and I'll see what I can do to help you out. Have fun, and be sure to report your results!
Thanks to member Wayhaw, I have a .doc file that will help a few folks with better descriptions and explanations. Let me know if you need a copy of this. Please include your e-mail address.
Original Post--Click Here