Having problems with drive on 2002 Cat Th83 handler. Basically plates have gone in the gearbox but am having problems identifying the cause. The solenoids test ok, The wiring between transmission controller and solenoids is ok. Tested output at the T/C end and it is not powering solenoid 2 in fwd gears and rev solenoid in 2 gears. Solenoid 2 is powered in rev but not fwd. So this has caused the damage in the gearbox but what is causing the T/C not to operate properly. I have taken it apart and found burnt out contacts and wrongly assumed this was the problem. I have a new T/C but its still not powering the correct solenoids for the correct gear selection exactly as the old one was. I can only assume its related to the input wiring into the T/C but don't understand these circuits well enough. I'm aware there is a transmission diode in the circuit which I have located but have no idea if this is faulty or not, or even what the consequence would be if its not working. Any help or guidance would be much appreciated. Cheers Martin
So you've had a clutch failure.? Which one, or more than one.? Got a machine Serial Number.? That would help in locating technical information including an electrical schematic. From what I recall that transmission is 4F/3R, so it will have 6 clutches total, 2 of which (1 direction clutch & 1 speed clutch) need to engage for any given speed. Clutches would be Fwd Low, Fwd high, Rev, 1st, 2nd, & 3rd. One clutch will be engaged in neutral.
Serial number is CAT0TH83H3RN05260. Yes its 4 fwd/3 Rev. Clutches are Fwd/Rev and 1sr,2nd,3rd 4th Hi Its Dana Spicer trnsmission same as Clarke Huth I believe. Clutch pack 2 is def gone, no pressure here but its the electrical side thats causing me a headache
No they ain't........ Fwd Low, Fwd High, Rev, 1, 2, & 3 is how they are described in the technical manuals. Speeds 1-3 in either direction is a combination of the Fwd Low or Reverse clutch and the appropriate speed clutch 1, 2, or 3. 4F is the Fwd High clutch & speed clutch 3. Do you suspect the signals from the Transmission Control are somehow compromised.? If you have replaced the Control with a new one then a harness fault would be a storng possibility. Would an electrical schematic be of any help.?
Yes the fault is at the T/C. The signals from the T/C are incorrect even when tested at the T/C end, so not a loom issue between T/C and solenoids. So must be an issue with the loom inputting power and signals to the T/C. I have downloaded an electrical schematic but it is very hard to follow on the computer when the pages are split up all the time. Would you know what the diodes function is?
Would you like a pdf one all on one page......?
I won't say no if its not too much bother
Keep an eye on your messages.
Quick look at the schematic in the area of the TC there are only 2 switched power supplies coming in on Connector F-C11 Pins 3 & 5, plus a wire #330 Yellow going out of Pin 7 that pulls in the neutral start relay. Everything else is signals to the solenoids. Interesting factoid. There are 6 clutches in the transmission but only 5 solendoid valves. There is a common solenoid valve for 2nd/3rd speed that, if my interpretation of the symbols is correct, engages the 2nd speed clutch when it is energized and the 3rd speed clutch when it is de-energized. That stands to reason because the 3rd speed clutch is also engaged when the transmission is in neutral, so logically the solenoid valve controlling it should be de-energized in order to prolong the coil life.
Thanks for the file, it opened fine the first time but has now stopped working and I cant view it. Yes 2 of the T/C plugs are output wires to the solenoids, its the other plug I'm trying to understand. Wires 330, 766B,766C,321 are the wires in question. I have 126B and 126C as switched power supplies to T/C. They are testing ok. Can you help with the 2 green wires 766, the brown wire 332 ? Do any of these supply power to T/C at any point? Am I right the 2 green 766 wires just operate the netural relay attached to the brake pedal pressure switch? Can you interpret what the transmission diode does at connector 14, orange and purple wire, one is wire 300 I think but cant view it atm. Apologies for all the Q's, unfortunatly I'm just a simple farmer trying to work this out without much engineering background so may be asking obvious q's
Have you tried donwloading it on to the desktop of a PC and open it from there.? The only power coming in to the TC is on the 2 wires coloured BLUE (wire # 126-PK) on the schematic. Did you miss this table.?
I need to correct that. The 2 wires 126-PK are energized with the key switch on. Wire 330-YL should also have Batt+ provided that the transmission neutralizing relay (Grid L-17) and the park brake switch (Grid J-13) are working correctly. Do you have incoming power on 330 with the TC in nuetral and the park brake switch in the ON position.? Wire 321-BR is an output for the backup alarm when the TC lever is moved to reverse. 766-F209 & 766-F210 are inputs from the transmission neutral switch (Grid F-6). The function of the diode is as a "arc suppressor" or flyback diode designed to prevent voltage spikes when the solenoid coil is de-energized.
I will check wire 330 for power in that state, I cant answer that with any accuracy atm. What I can say is that the handbrake does stop drive when in on position. Let me have a look. Do you think a faulty diode could cause backfeeding issues in the T/C? Bearing in mind I havn't connected any output wires from the controller to the solenoids as yet?
Seeing as the diode is on the output side of the TC I can't see it having any impact if you have the wiring to all the transmission solenoids disconnected at the moment. I would stand corrected on that though. I think you might need the services of a good auto-electrician. That transmission control circuit is not the simplest thing in the world. Even I am battling to understand how it works from the schematic.
If only I knew one. Do you know any Cat experts on here? There is voltage at wire 330 in neutral with the handbrake either on or off. The other odd thing is if I part the plug and check for output at terminal for wire 330 either side of the plug there is no voltage. It is only present when the plug is connected. What do you think if I disconnected all the wires out of this plug except the 2 switched powers to remove all the nonsense from the T/C circuit to see if this solves the output problem? This would just remove the handbrake and trans neutralizing aspect to allow for testing?
Which connector exactly are you referring to.? F-C11 the 10-pin connector right next to the TC.? I hope you are aware that the voltage on wire 330 is coming INTO the TC not going out from it.? It might be an idea. Post a photo of the connector where you propose removing the wires. It might need a special tool to get the wires out of the terminal. Don't panic too quickly, they are only plastic and proably cost less than £1 each. EDIT: Thinking about it a bit more it may be that correct TC function is dependent on receiving voltage on wire 330 to work right.?
Not sure of plug number not at a desktop to look but yes the one next to the T/C.
I'm at the side cutters level already
Binder twine and baling wire repair is it then.? Where are you located.? I can ask around to see if anyone knows a good auto-sparky in your area.
This one.?
in theory it should only have power with the handbrake If theres a chance it will work i will give it a go. Im in cornwall, england, uk
Yes thats the one
I've put the word out. If I hear anything back I'll let you know.
Are you able to tell me what the H number means on the schematic? The ones linking the blocks on the diagram
Harness perhaps?
"Highway" actually. A group of wires that go from one point to another on the schematic, and physically on the machine where they are encased in a protective cover. It's easier to draw them as a single line labelled "H-something" that you can follow on the schematic than draw each wire separately. If you look at any highway you will see exactly the same wires go in at one end that come out at the other. Where one hanress Part Number changes to another on the schematic the connectors are marked as below. The one on the left is Harness A, Connector #1. The one on the right is Harness F, Connector #46. If you go to Page 8, Grids C-2 & D-2 you will find a table that translates those letters to Part Numbers and describes the function of each harness.