M6040 Starter Relay Fuse blowing

[SoutheasternSon]

This was a problem the tractor had before I bought it, but I didn't know it until later. It wouldn't crank one day and I found that fuse was shot. A 10 amp was in in place of the 5. I put a 5 in and it was okay for quite a while, then it did it again, replaced and it lasted a short time. I was doing hay so I would just stick a 30 amp in to start it, and then remove it. This of course led to the 30 staying in and me forgetting about it until it blew the 30 the other day.

I found the thread from last week with a guy with the same problem. His short was in his HST pedal or something, which obviously isn't my issue. I checked the PTO switch by jumping it out, and that isn't it either. The shuttle neutral switch was replaced when this happened before, so it's pretty new. I checked all the small relays under the dash and they all have the same continuity so I don't think they are shorted internally.

This pretty much narrows it down to a wiring short somewhere, yeah? All the wiring I've checked so far looks solid. It's all loomed up and tight, but I haven't looked it ALL over.

Am I on the right track? Is there a common failure point for this circuit? I've attached a wiring diagram if that helps.

Thanks

 

[Dave_eng]

5 amp fuse circuit looks quite simple.

I would be checking around the shuttle neutral switch and wiring. Then the start relay (#8) itself.

#13 pto safety relay is only in the circuit as a set of contacts not a control so far less likely to be a problem.

Usually the same type of relay is used in several places so by carefully checking you may find a relay to substitute for the start relay to see if the problem goes away.

The instrument panel is also fed from the 5 amp circuit but since the problem only offurs during start the panel can be ruled out.

The Glow Plug relay is also using the 5 amp fuse. Since you do not know when it is momentarily in the circuit, I would try removing that relay since it is warm now and the engine will start without the GP's.

Buy a bunch of 5 amp fuses as using a 30 amp may turn a small problem into a very big one.

Dave

 

[SoutheasternSon]

Thanks for the reply. I will crawl under and check that wring good. It is exposed to the underside of the tractor, so I can see where it could have a bare spot. The starter relay and the glow plug relay are the same. I have had to replace the starter relay before, and I used the glow plug relay in it's place. I'll pull the glow plug relay and see if that changes anything.

What's strange is I got it to start 2 times today on a 5 amp fuse. The third time it shot. I noticed it looks like the cluster is fed from the same 5 amp fuse, but it also has it's own fuse in the fuse panel. It shot the other day before the starter relay fuse did. I pulled everything apart to look for a short but found nothing. I cleaned the main plug for the cluster and put some dielectric grease in it and all has been well. I wonder if they could be connected?

If found this a few more pages in with ways to troubleshoot most of the switches. It helps me understand the starting circuit better. I'm not very fluent in schematics. I will work on this more tomorrow and report back. Thanks!

 

[North Idaho Wolfman]

It would really help if you identified which 5amp fuse you are blowing.

 

[SoutheasternSon]

I suppose you're right!

The current starting problem is because fuse "J" in this panel keeps blowing. A couple weeks ago, fuse "D" shot and the gauge cluster quit working, but everything has been fine with it since I cleaned and greased the main cluster plug.

 

[Tx Jim]

I think I would remove starter & have it checked for a short & as Dave suggested check/change starter relay.

 

[North Idaho Wolfman]

Pull the starter relay and see if it still blows the fuse, if it doesn't then it's the relay, if it does then it's before the relay.

 

[BruceP]

I have reviewed the schematic you provided above... that 5a fuse supplies power to several relays on the machine.

BTW: That 5a fuse DOES NOT supply power directly to the starter. It is not possible for the starter to blow that fuse.

My approach would be:
1) install a 'dim bulb' tester inplace of the relay
2) try to reproduce the issue (the bulb will get bright when the high-current is drawn)
3) Remove all the relays and see if the problem goes away
4)... troubleshoot from there.

I would focus on relays 8, 12 and 17. (all connected thru this 5a fuse to "a" on the schematic)

...some other thoughts:
*)You did not describe under exactly what conditions this fuse blows.
*)It sounds as if the starter circuit works just fine before the fuse blows. (not the problem)
*) This leads me to think that the issue is intermittent....perhaps a wire rubbing on the frame AFTER the engine starts.

 

[SoutheasternSon]

Thanks for the replies.

I'll start by better describing under what conditions the fuse blows. Once in a blue moon, this fuse starts acting up. Sometimes, you turn the key the start position, the engine will make a half revolution and then the fuse will blow. Sometimes, when you turn the key to the on position, the fuse blows. It will go months between episodes. The other day I had been moving hay and had started and stopped the tractor a handful of times with no issues. My wife got on because she wants to learn to drive it, but it wouldn't start. I don't know if it blew when she turned the key to 'on' or 'start'. But the fuse did blow.

This was a 30 amp fuse, so I thought that the problem had finally reached the point it couldn't be ignored any longer.

I tried most everything suggested here this morning, except pulling the starter. I crawled under and looked the shuttle safety wiring over and everything seems to be ok. The wiring from the switch is good, it's only a year or so old. The wiring in the harness to the shuttle switch seems solid and the loom looks fine and isn't loose. I pulled the glow plug and starter relay, checked them both for them to "pull in", and they did. I ohmed them and they showed 0s so they are good. I pulled the glow plug relay and put it in the starter relay hole.

Now here's the issue. As quick as the problem appears it's gone.

As I was troubleshooting removing and testing relays and the like, I shot one 5 amp fuse and that's it. Now everything works fine. All the relays are installed, everything works fine and the fuse doesn't blow. I jumped the stater solenoid, drove the tractor 1/4 mile home and started trying to figure out what was wrong. That's it. I haven't don anything that should have fixed it.

This is frustrating. Not only is it intermittent as in its only when starting, but it happens and then disappears for 6 months. My mind tells me this is a wire somewhere. Surely a failing relay doesn't go this long. I haven't checked all of the smaller 5 pin relays, however.

Thanks again.

 

[BruceP]

Another approach to troubleshoot: (I am assuming there is intermittent short to frame on the (a) section of the circuit)

Disconnect the battery for this test!!

1) Use a meter with "beep" function to tell you when there is a 'short'.
2) Remove relays 8, 12 and 17.
3) connect meter between frame (gnd) and the NON starter-switch side where the fuse plugs in (fuse is removed from ckt)
4) Wiggle, jiggle, pull, tug and otherwise play with every wire-harness you can find.
5) If the meter beeps.... you are getting close to the problem.

Also note that the schematic shows this fuse is DIRECTLY wired to the alternator. (the schematic may be wrong. It does not make
sense to me that the alternator would need power only when cranking the engine.) ...but if the schematic is correct, it is possible
the alternator itself may be at fault.

 

[SoutheasternSon]

Sorry it took so long to get back with you.

That's a great idea. It's still doing fine, but the next time it acts up i'll start checking the frame for continuity. I don't know why I didn't think of that, but it should put me very close to the problem.

Thank you. I don't know how long it will take for it to act up again, but when it does I will report back. It might be weeks or months. But I won't forget.

 

[SoutheasternSon]

Well it's not the same issue, but I'm going to update any way, maybe to keep this out of the archives, and maybe it will help someone.

The tractor developed another electrical problem. As mentioned above, the gauge cluster would intermittently quit. No gauges, no headlights and no back light for the gauges. It didn't blow the fuse for the cluster, it would just quit working for a while, then it would start again. A few weeks ago, it quit and stayed quit. I gave up. I don't have time to troubleshoot it, so I carried it to the dealer.

They weren't excited to chase an intermittent electrical problem, but they did a good job. The reason the cluster went out was that it finally shot the fuse, but I didn't check it before I carried it. They also found broken wiring from the harness to the headlight switch plug and from the switch plug to the switch. Everything is working as it should now. The 5 amp solenoid fuse hasn't blown since August or whenever I posted this thread.

The mechanic claimed that this wiring chases it self in circles. He explained it in more detail, but that's the gist of it.

Was this the problem? Who knows? If it does it again, you'll see another update.

Anyway, fingers crossed.