Weekend Freedom Machines banner

1 - 19 of 19 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter #1
When doing the indicator light prechecks I only get the battery discharge light on when the key is in the "run" position. Supposed to get the oil pressure light, water temp light, low fuel light, and preheat lights. It's hot outside so I wasn't really expecting to get the glow-plug or preheat light on but the other three don't seem to work . . .

Here's what I've done so far:

Grounding the ends of the wires that go to the oil pressure switch and water temp switch do not make the lights come on.

The bulbs are good there's just no power to the socket (I checked the bulbs on the battery socket and they work fine)

The fuses are all good and have power to them

The previous owner disconnected the seat sensor which seems to be on the same circuit so there is one side of a connector not connected to anything above the fuel tank (under the seat.)

If I follow the tech manual I get to the point in the diagnostics where it usually says the wire between the 10A fuse and bulb socket is bad or open and to replace wire. How the heck do I trace that in the mess of wires behind the dash? What am I missing? New to this tractor so I'm slow working through it. Any help is appreciated!

James
 

·
Registered
Joined
·
711 Posts
When doing the indicator light prechecks I only get the battery discharge light on when the key is in the "run" position. Supposed to get the oil pressure light, water temp light, low fuel light, and preheat lights. It's hot outside so I wasn't really expecting to get the glow-plug or preheat light on but the other three don't seem to work . . .

Here's what I've done so far:

Grounding the ends of the wires that go to the oil pressure switch and water temp switch do not make the lights come on.

The bulbs are good there's just no power to the socket (I checked the bulbs on the battery socket and they work fine)

The fuses are all good and have power to them

The previous owner disconnected the seat sensor which seems to be on the same circuit so there is one side of a connector not connected to anything above the fuel tank (under the seat.)

If I follow the tech manual I get to the point in the diagnostics where it usually says the wire between the 10A fuse and bulb socket is bad or open and to replace wire. How the heck do I trace that in the mess of wires behind the dash? What am I missing? New to this tractor so I'm slow working through it. Any help is appreciated!

James
With your multi meter, you can check for continuity from one end of the wire to the other. Check for corrosion, could be that a connector has so much rust, the increased resistance drops the voltage down to negligible. Had this issue with my headlight switch on the 212.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
15 Posts
Discussion Starter #3
Thanks Bill, I'll give it a try. I'll have to figure out where the splices are to check the continuity in several spots.
 

·
Registered
Joined
·
15 Posts
Discussion Starter #4
Ok Bill and any other JD electrical gurus. . . so I have continuity on the 620 wire between the oil pressure sensor and the indicator light, I have continuity between the oil pressure indicator light and the coolant temp indicator light (#516 wire,) I have continuity between the coolant temperature indicator light and the coolant temperature sensor . . . . I have continuity all the way along that portion of the harness until I get to the seat switch which is gone and must be bypassed somewhere? All I have under the seat is a single open connector with no seat switch on it. It has to be bypassed somewhere I suppose because I can run the PTO and everything without any problems . . . It looks like the seat switch circuit also runs to the time delay control module? I'm trying to figure out where to go from here . . .
 

·
Registered
Joined
·
711 Posts
You have continuity, which means the circuit is not open. However, this does not mean you have 12v at the light. Measure the voltage going to the lamp. There could be corrosion somewhere creating so much resistance that the lamp only see's maybe 5v.


Sent from my iPhone using Tapatalk
 

·
Premium Member
Joined
·
7,563 Posts
I think your wiring is super hacked.

All those wires need isolated power supplied and when the switches ground to light the indicator. Id look behind the pto switch, it should have 5 wires conneced.

Thinking about bills comment, the light bulbs would show conductivity.

The orange wire also on the output of the lights returns to the ignigion switch and passes through to ground. Check for 12v there in run and at the lights as bill mentioned.
 

·
Premium Member
Joined
·
8,180 Posts
James,

I presume you have the wiring diagrams from the TM1591 since you quote the wire numbers. Some of the wires you mention are from the lamp to the sensor and would be considered the 'switched' side of the circuit...but I suspect your issues are related to the supply side or the 12 volt harness splice associated with the lamps.

I hate it when a PO hacks up the wiring harness as it makes it difficult to troubleshoot until it is restored to factory configuration, but we will try to work around that. The 10 amp fuse powers these lamps plus other loads, and in fact the battery lamp and all the other lamps you mention plus one side of the seat switch are powered from a common harness splice (shown as the heavy line in the diagram) so if you have power to one you should have power to all of them. Measure with a voltmeter and not an ohm meter...

For your tractor to continue running and the PTO to operate when the ground speed lever is out of neutral, the seat switch's normal function as a logic input to the TDCM has to be substituted somehow -- this means that there needs to be 12 volts present on terminal x14 pin 9 when the key is in the RUN position. Look in that area for the PO hack -- of course much more that just that may have been "modified" so who knows...

Chuck
 

·
Premium Member
Joined
·
8,180 Posts
By the way, you showed the version of the wiring diagram that applies to earlier serial number tractors -- is this the one that applies to your specific tractor? The terminal numbers that I quoted for the TDCM were from the newer version...
 

·
Registered
Joined
·
15 Posts
Discussion Starter #10
I haven't had enough time to be able to get at the TDCM but I have 12V to the 10A fuse that is supposed to power that circuit but no voltage at any of the indicator lamp sockets. So I think my issue is between the fuse and the seat safety switch (which is the first item in the electrical schematics after the fuse, am I reading that right?) The difficulty I'm having is tracing that wire through the wire looms to find the first split off the harness.

Just FYI to make sure I'm doing this right . . . I'm checking for 12V with the key in the on position to each of the sockets of the indicator lamps. I also seem to have 12V to the wire from that circuit to the voltage regulator. I don't have power to anything on the rear of the tractor either (brake lights, seat switch, wires that go into the fuel tank.) I'll go back to searching for the culprit in the next couple days.

If anyone has any other ideas on places to check please let me know. I'm going to try to start at the "terminal x14 pin 9" Which I'm assuming Chuckv is referencing on the TDCM? I'll post my findings there when I'm done.

While we're talking about electrical and indicator lights . . . what does the diode do that's behind the engine oil pressure lamp socket?

Thanks for all the help! Sorry I'm new with JD's and this tractor so bear with me
 

·
Premium Member
Joined
·
8,180 Posts
James,

Yes the seat switch is the first parallel load on the 10 amp circuit as shown in the schematic -- but it is just a tap point and if the switch is not there it should not effect those loads further down the network if the wires are intact. The battery discharge light is powered from that same network so it must be getting voltage from somewhere...hence all our discussion about verifying the harness splice (heavy black section of the network shown on the drawing...) for any pulled out wires, corrosion, etc. I am sure as you chase things down with your voltmeter you will find the issue. Good luck and keep us informed.

Chuck

The diodes that are drawn adjacent to the key switch are there to provide lamp test when the key is turned start...but they are connected to the low fuel lamp and the engine coolant lamp, not the oil lamp. Are you sure the sockets have not been swapped in the dash panel cells?
 

·
Registered
Joined
·
15 Posts
Discussion Starter #12
SO my diodes are on the front and rear PTO lamps and they were burnt up. I'm replacing them tonight. I don't see any diodes on the Engine Coolant lamp and the low fuel lamp . . . . I assume there should be a diode jumping from one side of the socket to the other like I'm seeing on my PTO lamps?

I also found the constant 12V supply to the pink/white seat safety wire in the TDCM. It was actually done very cleanly so I don't think that's the issue. The connector I'm seeing beneath the seat is a pre-wire for a rear PTO. He eliminated the connector for the seat sensor altogether.
 

·
Premium Member
Joined
·
8,180 Posts
James,

The lamp test diodes that briefly operate the lamps to verify their bulbs that I was mentioning in my earlier post are V1 and V2 that you can see right at terminal G of the key switch in the main 332 schematic. In that same schematic you will find small diodes across both PTO indication lamps -- those are there to snub the high voltages that can be generated by the collapsing fields in the PTO electromagnet windings when they are shut off, and help to prolong the life of the bulbs. You will find that there are NO DIODES required across the other indicator lamps and none are shown in the schematic.

I am curious as to how you may have determined that the diodes across the PTO lamp holders are 'burned out' as to check this you would have to remove the bulbs themselves and with the key turned off measure the resistance across the two terminals of the socket (across the diode...) with the meter leads first on one orientation and then in the other -- you should get a high resistance in one direction and a low reading in the other.

Having a constant 12 volts at the seat sensing terminal of the TDCM completely negates the safety circuits that were built into your tractor for "operator present" and is something I would repair immediately if it were my tractor.

Sounds like you continue to find out things about how your tractor's harness was hacked up...keep at it until you find out why there is no 12 volts present on the harness splice side of the lamps that do not work as they should. Some pictures of the splice might be useful if you can post them, and keep us posted on what you find. Good luck...

Chuck
 

·
Registered
Joined
·
15 Posts
Discussion Starter #14
Ok so some progress today . . . . To answer your question about the burnt up diodes . . I gently touched them and they crumbled in my hands so I just figured they were burned up. Problem now it that I think I may have shorted the PTO switches with the diodes missing to snub the high voltages because when I go to turn the front PTO switch on it burns up the 25A fuse and when I check continuity and voltage between the input side of the switch and the output side there is none. Thoughts?

Today I found a cut wire leading into the bulb socket for the glow plug indicator lamp, just a snubbed end with no corresponding loose wire under the dash. I think what this guy did was just cut out the entire section of the harness that came from or went to the seat switch. I think the wire from the seat switch fed the glow plug indicator socket and thus continued down the line to the other indicator bulbs. There are no taps or splices to a main wire anywhere on my tractor. It looks like he ran separate wires to each component similar to home-run style wiring you'd see in a house. So . . . I brought 12V into the glow plug socket from alligator clips from the fuse block and all my indicator lamps came on! Great! Or so I thought . . .

So here's what happens now . . . the battery discharge lamp and coolant temp light don't come on at all in the run position so I found that they had 12V from the input side to chassis ground but didn't have ground to the ignition switch. If I take the ends of the diodes off the ignition switch and put them to chassis ground they light right up in the run position. Are the diodes backwards or are these only supposed to come on in the start position?

Not having the wiring harness stock is making this extremely difficult to trace using the schematic but you guys are helping a ton! Thank you! I promise this will be over soon!
 

·
Premium Member
Joined
·
8,180 Posts
James,

If those diodes across the PTO lamps were a fried as you describe, the PO must have reversed and shorted them directly in his various wiring modifications.

Good find on the cut wire -- more evidence of his wild and harmful hacking. Here is a bit more information that you might find helpful: the coolant lamp will not come on in the RUN position unless the engine is already overheated...this is why there is a test diode on the START position of the key switch. In a properly maintained tractor that would be the only time that lamp would be lit... The same situation goes for the low fuel lamp.

Chuck
 

·
Registered
Joined
·
15 Posts
Discussion Starter #16
Screen Shot 2016-08-17 at 8.52.55 PM.png This is what you're talking about right? The diodes on the G (I assume ground) connection of the ignition switch? I think the diodes might be backwards and maybe that's why they're staying on all the time? Is there any way to confirm if the PTO switches are junk other than checking for continuity in the different switch positions?
 

·
Premium Member
Joined
·
8,180 Posts
James,

If the diodes were backwards then the lamps would never light at any position of the key switch. Of course, we are presuming that the key switch is internally wired as shown in the diagram and has not been replaced by something that is entirely different inside...

I believe that you have the TM1591 manual, so look at page 240-20-7 for the lamp test summary and the illustrations of the key switch -- I have excerpted it here for you just in case...
lamp tests from TM1591.jpg

From that page forward to page 240-20-21 gives lots of detail on lamp testing and function, then on pages 240-20-22and 240-20-23 the testing of the PTO switches is detailed.

Chuck
 

·
Registered
Joined
·
15 Posts
Discussion Starter #18
Finally figured everything out . . . . So the diodes were fine but they had a direct ground wire spliced in so instead of only being grounded when the switch was in the start position, they were grounded all the time (hence why they were on all the time.)

Because the diodes were junk on the PTO indicator lights they allowed the voltage to pass through to the switches and fried both of the PTO switches. Replaced the switches and put new 1A diodes in and everything seems to work fine!

When the PO did all this wiring he put the light circuit on a separate fuse in a separate fuse block. I made up a second fuse terminal in that block and ran a fused 12V hot to the glow plug indicator lamp with a 10A fuse to power the indicator light circuit. I don't see any reason that this would cause me any problems. The #500 wire that is supposed to feed that circuit is still present in the fuse block with a 10A fuse but it only goes to the voltage regulator. I suppose I could have spliced off of that to be more like the factory setup but at least I'll have less components to troubleshoot if I blow a fuse.

THANK YOU for everyone's help!
 

·
Premium Member
Joined
·
8,180 Posts
James,

Glad you got it all working!! Keep good notes on what you added/changed so you (and your heirs) will know how it varies from factory in the coming years...

Chuck
 
1 - 19 of 19 Posts
Top