STX38 No Start (under-voltage/relay buzz/solenoid?)

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  #1  
Old 08-24-16, 02:47 PM
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STX38 No Start (under-voltage/relay buzz/solenoid?)

Hello,

I turned my mower off today and when I tried to restart it, absolutely nothing. Finally, the relay (I found out this mower has the starter assist kit, which I didn't know wasn't original) made a buzzing noise. From what I've researched, this means it is receiving too little voltage. How should I go about testing to determine where my problem is? I do have a multimeter (with limited knowledge to go along with it, so if you can help please feel free to explain it like I'm 5 years old).

Edit: I forgot to add that if I touch a screw driver to both studs on the solenoid, it won't turn over. However, I used a test light and saw that I am getting power to the hot wire on the solenoid.

Also, I found a schematic online and ensured that all my wiring is correct (with the exception of the reverse of the 85 and 86 blades on the relay, which power the coil, but I don't believe the direction of this matters, particularly since this is how the mower has been in operation since I've owned it).

I also checked the wire that goes from the starter switch to the relay and found it to have continuity, ohms similar to other good wires that I tested it against (.2-.4). I ensured the PTO switch is functional. The relay is buzzing, and the buzzing quits when the PTO switch is engaged, so that lets me know the safety portion is working. I checked for voltage at the switch where the wire from the relay goes.

The only thing I can notice is that the solenoid will not engage when I put a screwdriver between the two ends. It will produce a small spark at times. However, I'm not sure why the solenoid would cause the relay to buzz.


Thanks,
Brandon
 
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  #2  
Old 08-24-16, 03:17 PM
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Sounds like a bad ground and or a bad solenoid. If you have a pair of jumper cables you can check a couple things.
First try and hook a cable end from ground on the battery to the engine as close to the starter as you can, then try the key again. If you have a 3 terminal solenoid, the bracket to the frame could not be making good ground.
If that fails, jump a cable from the positive of the battery to the positive lug on the starter. It should spin the engine. If it does, and you have power to the small terminal on the solenoid with the key in the start position, then the solenoid is bad.
 
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Old 08-24-16, 03:33 PM
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Thanks for the response. I'll give that a try. I also forgot that when I went to start it, it made somewhat of a "thud" and then nothing from there. I spun the engine manually, and it spins fine, so the starter gear is not stuck on the flywheel.

Thanks again,
Brandon
 
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Old 08-24-16, 06:49 PM
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Need a manual for this? Let me know.
 
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Old 08-24-16, 07:06 PM
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Sounds to me like the battery died on you or the battery connections quit making good contact.
 
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Old 08-24-16, 07:45 PM
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Well, I was thinking a similar thing about the battery, but when I tested it everything showed 12 volts. The battery, at the hot post on the solenoid. The wire from the ignition switch that activates the relay (starter accessory relay) only showed about 7 volts, if I remember correctly.

I have an "operators manual," but if you had a shop manual I'd really like to be able to have one of those.

Thanks,
Brandon
 
  #7  
Old 08-25-16, 01:19 AM
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What does the battery voltage show with a load on it? A bad battery can still show 12 volts. Test it under load to see.
 
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Old 08-25-16, 06:14 PM
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Today I ran a jumper wire straight from the + post on the battery to the plug in on the solenoid and the engine turned over, so I'm going to rule out a solenoid problem. I cleaned every contact point I could find and I've replaced the relay. The relay still buzzes when I turn the key to start. I tested the voltage at the hot post on the solenoid. It is over 12 volts. I tested the wire from the relay to the hot post on the solenoid, it was over 12. The wire that runs from the relay to the prong on the solenoid has nothing until the key is in start, which I presume is correct, but when I turn the key to start it is only getting about 9 volts. Is this too little? Should it be getting the full 12 volts?

I just don't really understand what's happening. If the contact wire going into the relay is 12 volts and coming out of the relay is 9, and its a brand new relay, then what else can it be? I'm stumped. I got my (very tall) lawn mowed today by running the jumper wire to the tab on the solenoid, but I cannot get it to do anything with the key except make the relay buzz. Perhaps someone knows what wires should have what voltage?

Would starting the battery with a jumper wire straight to the solenoid give an accurate reading to test the battery under a load?

Thanks,
Brandon
 
  #9  
Old 08-26-16, 02:53 AM
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I would take a look at the wire running from the ignition switch to the solenoid tab and clean it at the ignition switch end. Also sounds like a bad ignition switch.
Is this a yellow ddeck or a black deck ??
This issue is a known problem on many John Deere riders and that is why the starter assist kit is there. You can pick up a new relay at a automotive store for under $10. Here is a post describing the wiring. http://www.mytractorforum.com/234-ar...y-install.html
 

Last edited by jl66redcpe; 08-26-16 at 03:09 AM.
  #10  
Old 08-28-16, 09:07 PM
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Yes, jumping it the way you did sufficiently load tested the battery, it's not that.

I agree that you might have a bad connection at the switch. Often times the battery terminal on the ignition switch rusts and causes low voltage problems.
 
  #11  
Old 08-31-16, 10:56 PM
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Well, I seem to have found the problem so I thought I would update in case someone searches for this in the future.

After doing a bunch of tests with the wiring and continuity and ohms, I couldn't find the voltage drop anywhere in the ignition system (the previous owner installed the relay starter assist). I was using alligator clips to go straight from the hot post on the battery to the prong on the solenoid. Sometimes it would work. Sometimes it would not. It depended on which wire I hooked to. Finally I began to notice a relation between how I hooked the alligator clamp on the hot post. If I hooked it one way, it would start with a jumper wire. If not, it would not start. It turns out there was a washer between two of the wires on the hot post that had corrosion on it. It wasn't very obvious from looking at it without taking the wires off. I took the wires off and found the smaller washer inbetween them and found it to be very rusted and corroded. I cleaned it with the wire brush on my grinder and it was starting fine. What was happening was that the alligator clips were sometimes bridging the connection, depending on how I positioned them.

All of that work for such a simple solution. At least I found it. Thanks to everyone for the replies.
 
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