TC35D Hydro Hi/Lo shift problem

[jinman]

I now have it working, since I got the right combination on the wiring. However, it will switch the solenoid to the rabbit side but the switch will not stay in that position. As soon as I let go of the switch it goes back to turtle. Could that be a relay problem? Any suggestions.

After checking the schematic, if your solenoid will switch to rabbit while you hold the switch, it is NOT a relay problem. It can be a wiring problem or an isolation diode problem, but not a relay problem. If the low-shift relay contacts are stuck in the turtle position, you will never get the solenoid to go to rabbit. That's because the ground path for the coil of the hi-shift (rabbit) relay MUST go through the de-energized contacts of the lo-shift (turtle) relay. There is a jumper in the circuit that can be removed to cause a problem. That jumper is between pins 6 and 7 of connector C8. It should be a violet colored wire.

I'm curious why you say you "got the right combination of wiring." Has the wiring been disturbed? Why are you having to work on the tractor's wiring? Do you have an Operator's Manual? If you do, look at page 3-41 and 3-42 for the schematic of this circuit. If you do not have it, I will try to scan it for you if you are able to troubleshoot this and want the exact details of the circuit. I can take you through this step-by-step and tell you exactly how this circuit works, but you need basic meter usage and wire tracing skills to check all the things I will ask you to check. We'll also have to check isolation diodes V3 and V4 that are used in the rabbit "latch-in" circuit.

 

[Gurney10]

Thanks to each of you. I have already tried switching the relays around to no avail. I will check the wiring that would go to the joystick, and also the grounding wires. BTW, my reference to the hot wire was just a reference to the wire which carries the positive current, not specifically that the wire was "hot". Sorry for the confusion.

 

[Gurney10]

Jim,

I did not see you reply prior to my last post. I do have a manual, but to be quite honest with you, I am somewhat electrically challenged, particularly when it comes to circuitry with relays, diodes, etc.; so please bear with me. I had replaced the hi/lo switch because the old one did not even light up, so I assumed it was bad. The wires had be disconnected for some reason at the solenoid either due to accident or on purpose, so I had to determine which was the positive and which was the ground. I am not all that familar with circuitry terminology so when you refer to pin pin#7 and #8 of connector C8, I don't know what you are talking about. Is this in the switch or somewhere else. There did not appear to be any damage to the wiring that connects to the switch.

All that said, I do appreciate your help.

 

[jinman]

Milton, not being able to do electrical troubleshooting and reading of schematics does complicate things a bit. I'll try to make some suggestions, but if you start replacing parts without knowing if they are bad, it can get expensive in a hurry. I'm posting the diagram I posted earlier below. To the right of the relays marked 3 and 6 in the illustration are two square modules. These are isolation diode modules. I believe the one at the bottom is the correct module for the rabbit/turtle range switch. The only way I could tell for sure is to remove it and see if your transmission will switch at all to high range even for a second. If it won't switch at all, then you have the right diode module. This module costs over $60, so you don't want to replace it on a hunch without knowing for sure it is bad. Maybe it's contacts are dirty and just unplugging and replugging it in will solve the problem. You can also swap it with the identical one above to see if it fixes the problem. On page 3-41 in your manual, there is a block on the right side of the page with two arrow looking things pointing down. They are marked V3 and V4. That's this module. Just below the arrows, there is a box marked C8 in the lower left corner and the U-shaped line below that box is the jumper I described in my last post.

So, the best I can offer you is to point out where the diode pack is and get you started by making a couple of swapping suggestions. If that does not work, I guess you need to take your tractor to a New Holland dealer to let them look at it. It would be a mistake to start pulling things apart if you don't have pretty good electrical skills. I don't want to have you do that at all.

 

[Gurney10]

Jim,

Problem solved! The voilet jumper behind the diode was the problem. The gentleman I bought the tractor from said he and his son had a landscaping business, but his son died from a motorcycle accident and the tractor had not been used for some time. When I initially removed the left side panel, there was an old rat's nest inside. I cleaned it out and looked for broken or frayed wiring, but could not see behind the relay/diode assembly. After your last post, I thought that maybe some wiring was bad behind the assembly, so I removed the screws that held the assembly in place where I could see the wiring better and sure enough the jumperwire had been chewed in two. After repairing it the switch holds in the rabbbit position and works as it should.

I would never have found it without your help. Thanks so much. By the way, have you had electronics training? I have had a considerable amount of mechanical experience, but never have had the opportunity to work around anyone with electronics training. Do you know of any handbooks, etc. which might be helpful?

Milton

 

[grainger12002]

This is a great site and its awesome to have guys like Jinma and others that help often and its even better when the problem is detected and repaired by the operator !!


Happy seat time !

Preston in CT

 

[jinman]

Wow! Milton you made my day. I'm sittin' here with a big grin on my face because I was able to steer you in the right direction.:thumbsup:

I often worry that my level of confidence comes off as arrogance. I don't mean it that way, but I have have been an electrical/electronic technician/engineer/trainer for so many years that this stuff is just 2nd nature. I try to talk to people without talking down to them. Many times I rewrite what I type because I don't like what it sounds like. I completely understand that a person cannot understand what they have never worked on and try to use terminology that they can understand. Perhaps that's what I've learned from many years as a trainer/training developer. I hope so.

It's hard for me to come up with a good starting point for learning electricity and/or electronics. One of the best books I've used in the past was a reprint of a US Navy Basic Electricity and Electronics Training Manual that I found in a book store. The problem with any of these manuals is they often take you down many roads you don't need. For example, why do you need to know about atomic theory and electrons in orbit. What you need is basic principles of DC and AC electricity and how to measure them using the most common and simple tools like a volt-ohm-milliammeter (VOM). In the case of troubleshooting the electrical systems on tractors, you only really need to know DC electricity and theory. You need the basic understanding of batteries, diode rectifiers, switches, relays, lighting components, and basic knowledge of motors and generators. Wiring and connectorization is a whole field within itself, but you have to know this too. This is all extremely important when tracing signals through harnesses of hundreds of wires and connector pins/sockets. It just goes on and on.

I don't know where to tell you to look for a good basic instruction manual. I can look online and get back to you on that. Often, I think you might find a local community college might have some basic classes where you can go and get training, but you will have to be patient and take a lot of info that you won't ever need before you get to the "good stuff." You'll also be surrounded by young students who are just kids. That's the reality of that environment. If you could find someone to mentor you while studying on your own, that would be best. If you have a friend who is an electrician or technician who will show you some basic test equipment like the VOM and how to do DC circuit tracing, it will be a big help. Having that person guide you is one of the biggest advantages you can have to being successful in your learning a new skill.

 

[guyw]

Jim,


I would never have found it without your help. Thanks so much. By the way, have you had electronics training? I have had a considerable amount of mechanical experience, but never have had the opportunity to work around anyone with electronics training. Do you know of any handbooks, etc. which might be helpful?

Milton

Milton,

As a youngster I remember reading a Radio Shack book that helped me understand a lot. I eventually went on to College to become an Electrical Engineer. I just looked at the Radio Shack web site, and they have a book titled "Getting Started in Electronics" for $19.99. This may or may not be the same book that got me started (it was a long time ago) but the customer reviews seem to be quite positive.

Guy.

 

[Gurney10]

Thanks to all who responded, I will check out the Radio Shack book. I hope I can be of help someday with a problem I know something about.

Milton
"Good judgement comes from experience, and a lot of that comes from bad judgement"

 

[ArtMech]

Congrats on solving an issue!
Yes, it really shows how important and good job the TBN does.
Well, I'm quite new in this site, but noticed Jim is among the guys you can always rely on.