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24V diagnostic

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Bob W

11-12-2002 16:21:45




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Hi folks; Was on the road doing calls today and ran into one of my old pet peeves-- the 24 Volt starting/charging system. I know these things did and do work well but I don't see them often enough to get practiced at them. I do know that the lack of knowledge can have disastourus results. (hey parts guys we need a complete wiring harness for a 4020) The one I was on today had just had a repaired generator installed and polarizred but GEN light stays on when the tractor is running. (all speeds) The wiring looks in reasonable condition and the customer had installed a doner regulator that was thought to be good. The tech manual helped as far as checking wiring to the key switch etc but is not laid out to let one do some quick checks using a digital volt meter. Can anyone give me a hand here? Thanks for reading-- Bob (BTW,G-Man if you are there, had any experience with the IVT yet? )

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WTW (IVT)

11-15-2002 12:26:55




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 Re: 24V diagnostic in reply to Bob W, 11-12-2002 16:21:45  
Bob, Do not claim to be an expert on anything but I have been around quite allot of stuff over the years. You know what an expert is don't you? An expert is a drip under pressure!! I have worked for JD dealers for over twenty years and here in the publications department in Waterloo for the last five as a vender employee and now as of 1 month ago have become a full fledged Deere & Company employee. Do not know what exposure you have had to the IVT but I was directly involved in allot of the diagnostic writing on it. I have moved from writing diagnostic procedures to diagnostic development. The IVT is a Hydro / mechanical transmission, meaning it has two inputs one being hydro and the other mechanical. If you want a full blown explanation on it read the theory of operation in the Operation and Test manual (I wrote it) and if you have questions after you read it holler and I will try to answer them. The transmission is not driven directly through the hydro as we know them in a combine, lawn tractor or skid loaders and like. It is a mechanical transmission (planetary) that is speed controlled by the hydro. Picture a simple planetary with a ring gear around the planet gears (example axle final drive unit or Powershift) The ring gear instead of being held by a housing or a brake it is connected to a hydro unit which will control it in many modes from rotating it very fast in one direction to slowing it down to a stop to holding it still to rotating it in the other direction and speeding it up in that direction. The hydro rotating the ring gear controls speed output of the transmission / planetary only. The hydro has no effect on the direction of tractor movement. Forward and reverse direction is done with a forward clutch and a reverse brake just like the PowrQuad transmission works. I am sure now that I started this explanation there will be more questions, which is fine. The most interesting fact about this transmission is that mechanically it is very simple, hydraulically fairly complex and electronically it gets pretty interesting. There is only a total of four clutch / brake type elements in the whole transmission compared to nine in a old 15 speed Powershift. It took a combination of four of the nine to make the old Powershift move, the IVT only takes one! One of the four elements is the parking brake and all it does is release the brake. One is a low clutch, one is high clutch and the last one is the reverse brake. Only one of these elements have to be engaged to make this tractor move. Yes the tractor does make a shift in the forward mode from low to high clutch but no shift is ever felt. Moving the shift lever forward in these tractors is one constant controlled speed from a dead stop up to top road speed. Very impressive to drive. I will quit here and see how many question this much stirs up. Take Care Dave W.

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Bob W

11-14-2002 18:05:10




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 Re: 24V diagnostic in reply to Bob W, 11-12-2002 16:21:45  
Thanks to all for the 24V info. I wish I up to speed on this better. WTW You may have opened a can of worms here.... Iwant to know more about you and this transmission. Us guys in the field really enjoy talking/working with you factory types wether its new or 30+ yrs old . Thanks again, Bob



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WTW

11-13-2002 13:18:45




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 Re: 24V diagnostic in reply to Bob W, 11-12-2002 16:21:45  
Bob, I will give you some quick things to check to try and isolate your problem. First make sure that the ground wire between the two batteries is connected. Ground wire located at the right battery rear negative post. Check to make sure you have power from both batteries to your voltage regulator and generator. You can use your volt meter to do this with the engine shut off. At the top of the regulator there will a terminal (A2 brown wire). Should have 12 volt negative ground when checking between it and the frame of the tractor. On the bottom of voltage regulator there will be 3 more terminals left to right they are Bat. Gen and F. There should be 12 volt positive ground at the Bat terminal (blue wire) when checking between it and the frame of the tractor. If you do not have the two 12 volt readings, ground wire between the two batteries is open or circuit from battery source is open. Now check for voltage between the A2 terminal and the Bat terminal. with your volt meter you should have 24 volt. If you do not one of the batteries do not have correct polarity or is connected backwards. If everything checks good to this point, bypass voltage regulator to see if problem is regulator or generator. To do so you will use your volt meter and two jumper wires. Leave volt meter connected between the A2 and Bat terminals to monitor the 24 volt charging circuit. With the engine running place the first jumper wire between the Bat terminal and the Gen terminal at the bottom of regulator, this will bypass the cutout in the regulator. You may notice the voltage is coming up, if so cutout in regulator is not working. Leave the first jumper wire on and momentarily place a second jumper wire between the A2 terminal and the F terminal, this will full field the generator. Voltage should climb up to 28 to 32 volt. If it will do this the generator is fine remove both jumper before shutting off the engine or you will burn out your generator when you do. Hope you can follow this. Should tell you where the problem is at. Good Luck Dave W.

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WTW (IVT)

11-13-2002 13:24:22




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 Re: Re: 24V diagnostic in reply to WTW, 11-13-2002 13:18:45  
Bob, Forgot to mention I could give you some information on the IVT also, I wrote a big part of the diagnostic section of the John Deere service manual on this new transmission. Pretty interesting stuff to a gear-head like ourselves. If you have any question I will try to answer them for you too. Just let me know. Dave W.



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JDGnut

11-13-2002 19:29:44




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 Re: Re: Re: 24V diagnostic in reply to WTW (IVT), 11-13-2002 13:24:22  
WTW.. I'm missing out on the newer IVT classes... what I picked up last year is fading fast.. lol... Not getting to help with the new trany class this year.. swamped doing my Cert classes... I'll take a copy of any info on the IVT... I was hoping to get one.. but not crossing my fingers... Marketing guys were down today.. going to do a customer clinic on the new trany in January... Man.. do they have all the money.. hahaa.. I hope things are going good your way.. Still slow going on the G.... JDGnut

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Russ

11-12-2002 19:55:09




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 Re: 24V diagnostic in reply to Bob W, 11-12-2002 16:21:45  
Grab the tech manual and make sure all the wires from the reg match the gen terminals. You will need to remove the wires from the generator to make continuity checks as the terminals are all connected through the windings in the gen. If it is an early model or 10 series you may need a new "wishbone" in the harness under the dash cowl in the harness.



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