955 - no power/no lights

[onthehill]

Well, I'm perplexed and hope only of you have some ideas. I have a 955 that has no dash lights when I turn the key and no crank. Here’s how it started, and what I’ve done to date:

How it started:

Tractor started fine until one day when turning the key I got dash lights until I tried to start it. When turning the key to start, I got a loud click and then everything went dead (no more lights on the dash/nothing). I disconnected the battery to swap out another one (figured it was dead) and got the same thing with a fresh battery. Now, however, I get nothing at all (no dash indicator lights, no clicking, nothing), regardless of key position.

What I’ve done to date:

* Tried a known good battery - didn’t help
* Checked the battery to frame ground. Also used a jumper cable (from battery to bolt on frame) - still need to figure out how to tighten down the bolt/nut but no better
* Checked frame to engine ground. Also used a jumper cable from the two bolts, just in case - didn’t help
* Checked voltage at starter - 12V
* Checked voltage at wire going from starter to ignition switch - 12V

Here’s where it gets interesting:

* When I turn the key to ACC (one click left or right), the voltage from the starter to the ignition switch drops to 1-2V. I’m also seeing 2V to the ACC wires coming out of the ignition switch.
* I tried to scuff up the ground wire that hooks on the end of the ignition switch but no difference.

So, what do you think? Bad ignition switch? No sure what the loud click would have been though. I’m also old getting a couple volts to the fuses. Although, I’m getting 10-12V to the PTO fuse (odd).

I’m totally stumped! Thanks in advance for the help.

 

[jaxs]

Those 1-2 volt and 10 volt readings scream bad connections,brokenn wires,poor ground or all of the above. With key on and a load (lights or such) voltage reading must be 12.5 or better at both power in and power out on ignition switch (no difference at all). If not,jumper the 2 switch terminals and retest fuse block and other places.
Let's step back and check a couple of things before doing any more troubleshooting. A digital read volt meter is almost a neccessity to accuratly test so if you don't have one,beg,borrow or steal one for this job. Read accross battery posts. You should have 12.6-12.8V. If it's less than 12.3v the battrey is discharged below 60% or shot. 12v is only about 25% which isn't enough to start anything. Once you have 12.5 or better accross posts,re-check wires,grounds and connections.

 

[hosspuller]

Jaxs is correct. His advice is the same as mine. Then explore the starter... It may be shorted

 

[onthehill]

Jaxs - the voltage at the battery is 12.6v. I’ll have to double check at the starter and at the ignition switch again but, if memory serves me, I was getting 12.2 at the starter and between 10-12.2 at the ignition switch. The posts on the ignition switch don’t look great so that might be contributing.

 

[jaxs]

Jaxs - the voltage at the battery is 12.6v. I’ll have to double check at the starter and at the ignition switch again but, if memory serves me, I was getting 12.2 at the starter and between 10-12.2 at the ignition switch. The posts on the ignition switch don’t look great so that might be contributing.

Those are excessive drops that must be found before moving foward. Something I've never experienced but I see happening to others is rotted wire/cable where it connect's to cable end. Hard to see inside cable cover unless peeled back.

 

[grsthegreat]

you can ohm out the cables to see if there damaged within the cable. Have you tried manually jumping starter with a screwdriver to make sure starter turns at all.

 

[onthehill]

@jaxs and @grsthegreat Let me try both of those suggestions and get back to you both. It might be a few days because I’m out of town most of this week.

 

[LouNY]

Or try a good heavy duty jumper cable from the actual starter positive to the battery positive,
after verifying twice that everything is in neutral.

 

[bmaverick]

@jaxs and @grsthegreat Let me try both of those suggestions and get back to you both. It might be a few days because I’m out of town most of this week.

1 of 2 possibilities.

1- The solenoid is shot in the starter.

2- The VR is shot and has an internal short that is not repairable. Both Yanmar and John Deere have a Technical Service Bulletin out for over 2-1/2 decades that address this. Get the newer style solid state VR.

https://www.tractorpartsasap.com/voltage-regulator-12-volt-new-denso-m805143-125437.html

 

[onthehill]

@bmaverick - any idea how to test if the VR is bad?

I’m going to do some troubleshooting tomorrow so I’ll let all of you know. Thanks for all the help.

 

[bmaverick]

Test continuity between terminals. You'll need the TM1360 JD Service Manual to follow the procedure.

TM1360, Section 240, Group 10 covers all the needed info you will need.

In Group 15, there is a cheesy hand drawn Charging Circuit. The entire SM is really detail until getting to this page, like it was an afterthought. LOL

 

[jd110]

Everything you have said screams that a battery cable or connection is bad. A perfectly good looking cable can be bad. You mentioned bypassing the negative cable with a jumper cable. Try doing the same thing with at the positive cable . Connect one end to the positive battery terminal and the other end to the starter post that the battery cable connects to. Another note, a bad voltage regulator will not keep tractor from starting if you have a known good battery in it. It can cause the battery to go dead, but not keep it from starting with a good fully charged battery.

 

[onthehill]

We’ll, I was able to figure it out. After spending an hour or two cleaning/testing the ignition switch, it turns out the problem was a actual the cable coming from the battery to the starter. I was reading 12.8v at the ignition switch but under any load (even the lights), it dropped to almost 0. Replaced the cable and all seems to be good. @jd110, you were dead on!

Thanks for all the help everyone. All of your testing ideas really helped me narrow this down.

 

[jaxs]

Had we not been stuttering and spoke with more clarity in post 5 & 6 it could have been fixed a week ago.