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Hello!

I have a 1980 John Deere r72 that won't start. The starter does not engage or turn or anything when I turn the key. The last time I mowed with it was last October, and I'm just now getting around to looking at it.

I checked the battery and it's reading 12.6, so it's ok.

I cleaned up most (all I can find) of the grounds around the tractor--still won't start.

I then tried to jump the starter. I did this with a set of car jumper cables and I got a lot of sparks but the starter did not turn. So I'm assuming this indicates a bad starter. Am I correct?

Just for kicks, I then went ahead and checked with my multimeter to see if the solenoid was getting power to the starter when I turned the key. I did this by reading the volts between the starter side of the solenoid and the negative battery. With key off it is 0. With key on it is still 0 (and I had someone sitting on the seat and the blade disengaged and transmission in neutral). So does this mean I likely have more problems than just the bad starter? Should I go ahead and replace the starter or continue diagnosing?

Thanks!

Here is a procedure that a few forum members came up with to help people with a no-crank condition. Let us know how you are doing.


Electrical* problems can be very easy or very difficult, depending on four things.
1. * How well you understand basic electricity.
2. *What tools you have and know how to use.
3. *How well you follow directions.
4. *You don't overlook or assume anything and verify everything.

Remember we cannot see what you are doing. *You are our eyes, ears and fingers in solving this problem. *You must be as accurate as you can when you report back. *The two basic tools we will ask you to use are a test light and a multi-meter. *If you have an assistant when going through these tests it would be very helpful. *These steps work the best when done in order, so please don't jump around. *Now let's solve this problem.

First, check the fuse(s), check battery connections for corrosion (clean if necessary) and *voltage - above 12.5 volts should be good.*

Second, check for power from the battery to one of the large terminals on the solenoid. *One of the wires is connected directly to the battery and has power all the time so one of the large terminals should light a test light or show 12 volts on a meter at all times.*

Third, *check for power at the small terminal of the solenoid while depressing the clutch/brake pedal and holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch). If your solenoid is a four wire solenoid, check both small wire terminals as one is ground and the other is power from the ignition switch. *If your solenoid is a three wire solenoid, make sure the solenoid body is not corroded where it bolts to the chassis of the mower as this is your ground path back to the battery. *If in doubt, remove the solenoid and clean the mounting area down to bare metal. *If there is no power to the small terminal then your problem is most likely a safety switch, ignition switch or in the wiring.*

Fourth, check for power on the other large terminal of the solenoid while holding the key in the start position (you may need an assistant to sit in the seat to override the safety switch).*

Fifth, check for power at the starter while holding the key in the start position (assistant again).*

Sixth, check your ground circuit back to the battery.

After you have gone through each of the above steps, let us know what happened when you did each step. *At that point we will have great info to tell you how to proceed. *Remember you are our eyes, ears, and fingers, so please be as accurate as possible.

Be as specific as possible with voltage readings as this will help diagnose your problem quicker. *If you do not know how to perform the above checks, just ask and I will try to guide you through it. *Youtube also has some videos and as you know a picture is worth a thousand words.

Thanks Lawnranger.

Surprisingly, this procedure isn't too far off from what I was doing. That makes me feel good.

I'll go through it and get back with you all.

But in the mean time, I did screw something up.

When I was taking my solenoid off, I had my hands reached up under the seat where I couldn't see and was pulling it out and I dropped it and all my wires got mixed up. If anyone knows the exact wiring of the solenoid for this mower (or similar), please let me know so I can confirm I got mine back together right!

The solenoid is the kind with two large posts and a small one. I have the purple wire (I think it's the transmission switch) on the small one. On one large one I have the positive battery cable and the red wire (the one with the fuse). On other large one I have the starter and another wire (it's actually two black wires spliced together) that goes into the wiring harness and to who knows what. Anyone know if this is correct? I can't find any diagrams that show this last black wire.

THanks!

allz28 said:

Thanks Lawnranger.

Surprisingly, this procedure isn't too far off from what I was doing. That makes me feel good.

I'll go through it and get back with you all.

But in the mean time, I did screw something up.

When I was taking my solenoid off, I had my hands reached up under the seat where I couldn't see and was pulling it out and I dropped it and all my wires got mixed up. If anyone knows the exact wiring of the solenoid for this mower (or similar), please let me know so I can confirm I got mine back together right!

The solenoid is the kind with two large posts and a small one. I have the purple wire (I think it's the transmission switch) on the small one. On one large one I have the positive battery cable and the red wire (the one with the fuse). On other large one I have the starter and another wire (it's actually two black wires spliced together) that goes into the wiring harness and to who knows what. Anyone know if this is correct? I can't find any diagrams that show this last black wire.

THanks!

Click to expand...

The good news is that you have a three connector solenoid and as far as the two LARGE red wires, they can go on either post of the solenoid (one red wire on one post and the other red wire on the other post). The small purple blade connector goes on the small terminal of the solenoid. Now for the black wire(s): does the black wire connector look like it would go on one of the large posts of the solenoid or to the mounting bolt of the solenoid? I would start by using a volt meter and test for voltage on that wire. Turn the key on and connect the red lead of your volt meter to the positive battery post and the black lead of your volt meter to the black wire(s) you discovered and see if you have a closed circuit. If you have a closed circuit then the black wire is most likely a ground and it would connect to the mounting bolt of the solenoid. If that is not the case then the black wire could possibly be a feed for the harness and you will have to remove all the black harness casing and physically trace the black wires to find out where they go and this would be the best way to confirm the wires in question. You could also try using an ohm meter on the black wires to the chassis of the mower to see if you have continuity and if you do then you have a ground wire.

Perform the checks and report back with your findings.

Sorry I'm just now getting the chance to work on this mower again and get back on here.

I just did your check of the solenoid wires and it appears the black wires are a ground. Thanks! I'll hook them to the solenoid mounting bolt.

Now, onto the other tests. . .

Hmm, where the solenoid mounts to the chassis has painted metal which seems odd for a ground wire.

Good News! The mower is fixed. You all are going to hate me for skipping around, but after I didn't find any power to the small terminal on the solenoid, I started checking switches and found that my blade position switch had a wire that fell off of it. Thanks for your help, especially with getting that solenoid wired back correctly!

Ahhh! I spoke too soon. Not quite fixed because I have a new problem. Mower turns over good now, but won't start. Just performed a spark test and I don't have any spark. Could this harken back to how the solenoid is wired?

Sounds like a safety switch is grounding the coil. Find the schematic for your mower and follow the diagram for the safety switch circuit.

I can confirm that you are right because I just took the ground off the coil and the mower started right up. When I put the ground back on, it turned off. :thumbsup:

The question is, why is a safety switch grounding the circuit? What am I looking for?

You've been awesome, Lawnranger.

MOWER is fixed FOR REAL this time! Yes!

You nailed it, Lawnranger. Couldn't have done it without you. The problem was that where the coil ground wire connects with safety switch ground wire, it was touching metal and getting an accidental ground.

Thanks again!

The safety switches will ground the coil in the event of an unsafe condition such as you fell off the mower while the blades are engaged. The "operator presence" switch is in the seat and if the PTO is engaged and the you lift your weight off the seat, the switch will ground the coil which in turn kills the engine. Now the question is which switch is grounding the coil? I'm a little concerned about the black wires you connected to ground at the solenoid. Usually there is a feed wire coming off the large post of the solenoid that is directly connected to the battery and this wire feeds the wiring harness up to the ignition switch so until you get a schematic and verify what that black wire is for then we may be chasing the proverbial tail.

I just saw post #11. Congratulations! Now what about that black wire I mentioned in post #12?

I'm assuming that black wire is a ground. I still have it hooked up to the solenoid mounting bolts and everything is working just fine. In fact, i just finished mowing the yard.

Hopefully it is indeed a ground but I'd still get a schematic out and look it up.

I have a r72 John Deere that we are working on in my ag class. I am the one in charge of it and am at a loss. It's not starting. I have power to the solenoid and back to the key switch. Is it the key switch or is it something to do with a safety feature?

khunsinger said:

I have a r72 John Deere that we are working on in my ag class. I am the one in charge of it and am at a loss. It's not starting. I have power to the solenoid and back to the key switch. Is it the key switch or is it something to do with a safety feature?

Click to expand...

Start your own thread and give us more information and we will be able to help. We are not there so we do not know what you have done. We also can not see or hear what it is doing. You have to let us know all of that.

I pulled off the PTO lever and all 4 wires disconnected leading my to believe that my ag advisor had someone else try to work on this mower. I do not know in which order they go in. Does anyone have a picture or something like that, that will tell me which wire goes where. There is also one hot wire in there

Well as this IS A LEARNING process we will play teacher.
Q1) what does the PTO switch do ?
A if you don't know go to the JD web site and read the owners manual

Q2)
Now that you know what it is supposed to do which wires go to the clutch and which wires are in the start circuit ?