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Discussion Starter · #1 ·
Working on my cih 5240 with elect problem. For rev solenoids not getting power.
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Can hear for, rev and latch relays click when shuttle switch is moved. tried swapping them around to see if one was bad, nothing. have continuity from solenoids back to their respective relays. have power at both fuses and from 10a fuse up to terminal 30 on latch relay. how to do relays work? I dont know enough about them to know were power should go from there.

Other oddities: neutral light comes on even though everything is in neutral and wont go out. recently replaced the dashboard beeper which should go off when the shuttle is moved with the park brake is engaged, but that isnt working neither.

guess my first question is where should 12v go once it gets to the 3B relay? or maybe someone had this problem before?
 

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I would say relay 3B isn't working. That would explain why the light doesn't go out and buzzer doesn't come on.

12 v is applied on terminal 86 of that relay and goes out 85 to ground. The rectangle on that drawing represents the relay coil which moves the contacts. Terminal 30 is the stationary contact, terminal 87a is the de-energized contact and 87 is the energized. Or better to call 87a the normally closed contact (NC), 87 is the normally open (NO) .

With no power to relay coil, the voltage will be applied from terminal 30 to terminal 87a as shown in drawing. When the coil is energized, the linkage drives the contact off 87a and onto 87 so now voltage is applied from terminal 30 and through to 87.

Relays should be shown in their denergized state on drawings. That is why the circuit from 30 to 87a is called the normally closed contact. Because if you had that relay in your hand it would obviously be denergized and so you would measure continuity from 30 to 87a.

So you can put an ohmeter across 30 and 87, energize the relay by moving your fwd/rev switch to make that relay 3B get power to coil and see if you get continuity across relay contact.
 

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Discussion Starter · #4 · (Edited)
So... ohmmeter across terminal 30 and 87, i do get continuity and 12v whenever i move the lever to forward or reverse with the key on. so i pulled out the forward relay 3D(can hear it clicking), swapped it with 3B. if 3b is bad, should now have reverse right? nope, still nothing.
 

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Don't know if this applies to your situation but I had similar problem on my JD7410 w/ LH reverser. A spring broke in the F/R shuttle valve and would not return all the way to the neutral position. The tractor has both a 'neutral' and 'not neutral' sensor on the valve spool and shuttle control. It would not activate the F or R valves unless it saw proper signals from both. I could still hear some relays clicking but no motion. I played with it a bit and the valve spool moved enough that it wouldn't even start. Ooops!
 

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If that relay 3B did in fact switch over and gave you a circuit from 30 through 87 then your neutral light should have gone out. Because the contact switched from 87A and over to 87 and so no more power to that light. You were saying the light was always on. If the light stayed on the entire time then it is going to be hard to figure out.
 

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I would check that power is only going through 1 relay at a time. Those relays fuse themselves shut inside. Otherwise you could put a jumper between 87 and 30 at the relay and see if it works. With the jumper you could then check that the power is getting where it needs to be
 

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Discussion Starter · #8 · (Edited)
If that relay 3B did in fact switch over and gave you a circuit from 30 through 87 then your neutral light should have gone out. Because the contact switched from 87A and over to 87 and so no more power to that light. You were saying the light was always on. If the light stayed on the entire time then it is going to be hard to figure out.
yes it should have. Im now not certain that the light im seeing is the one shown in the diagram. Diagram says neutral indicator light, one im seeing says Shift to N (which is intermitten, sometimes it will come on and stay on, sometimes its off). and while i can get 12v at 87, that means my forward relay should get power and then i should move, but im not getting 12v on 30 of relay 3D. i could jump that wire and see if i am able to move.

what function would 8, the latch relay diode module have? there are connections into it from the terminals im testing

maybe someone else will know. my s/n is 1059899. is there a later diagram i should be looking at instead of this one?
 

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The diagram says it's a latching relay, but I'm not sure exactly how it's latched and how it's released. Usually it's all done with the wiring, not a special relay.

If you put the relays on the bench, if you provide 12v to the coil terminals, you should be able to ohm out the other contacts and know that they are working and that the normally-closed is in fact opening.
 

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Ok, to get that 12v to term 30 of 3D, you need to have relay 3B energized. If the contact on 3B does not change over then no power through 3D (or 3C) to get your forward (or reverse) solenoid to activate.

As Torrie says, maybe take relays right out and put them on a bench to see if they work.

And yes Torrie, I noticed the same about the "latching" relay. But if we start second guessing the accuracy of the prints then we may as well call it a day. I think the people who created the drawing simply made a poor choice of what to call the relay. I see nothing on the drawing to indicate it is a latching because there is no circuits shown to unlatch it.
 

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As far as I know the diode doesn't act as a latch. The diode is there to absorb the current when the relay is de-engergized. It gives the coil a place to dump it's energy. The diode is placed in parallel with the coil, but with opposite polarity. In other words the arrow points towards the +12v side of the coil. In this configuration it's called a flyback diode.

Not sure how a diode would latch a relay. A latching relay involves using the normally-open contact to provide 12V back to the coil so it stays on after it's been initially energized (it switches itself in effect). Then there has to be a break in the power to unlatch it.
 

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We’ll it’s only been about 20 years since basic electronics but that diode is polarized to flow current to the energizing coil after relay makes contact therefore “latching” the relay.
Yes only power cycle unlatches it. The flyback diode is in the relay which should be directly across the coil which the external diode is not.
I’d check that pin 86 is getting 12v when you move the lever either forward or reverse from the neutral position. If it is the relay should energize and send power to pin 30 on the forward/reverse relays.
Wouldn’t hurt to check that latching diode with a multimeter because I’m guessing there’s only a momentary contact at the shift gate, if it’s not latching and holding your forward/reverse relays will function and you can hear them clicking but have no power.
 

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Torrie has it right, the diode is there to discharge energy back through the coil when deenergized. Notice all the other "not latching" relays have same diode shown. When the power is removed from coil 3B, that relay will denergize. Nothing on the drawing says otherwise.

A latching relay is one that remains in its operated state after the coil is deenergized. There is either a second coil installed to unlatch the relay or a mechanical mechanism to move the contacts back to their reset/denergized position. Nothing on the drawing shows a delatching scheme. Young Farmer can confirm easily enough as I would bet all relays are exactly the same.

I understand Joe is looking at that external diode assembly, what you need to do is look at what happens if all wires are removed from terminal 86. That is how a guy defines a latching relay. Those external diodes I beleive discharge power stored in the downstream circuits when relay 3A opens.
 

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For the love of god it isn’t an actual latching relay but diode across 87 and 86 latches it when the relay is energized. Therefore “latching relay”.
Its no flyback diode and flyback from what?? And sink this supposed current right into the relay coil???
The actual flyback diodes for the control solenoids is 13 and notice the polarity. No current flow when energized, clamps reverse current when the relay contact opens.
 

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You're correct. We are just talking past each other. The flyback diodes are in parallel with the coil. Looking more closely I can see that the diodes in the #8 spot are what make the latching mechanism. Specifically the diode at #8 is to direct the current flow such that when the shuttle shifter sends 12 volts to 86, that that power will not also loop around to 87 and prematurely activate the solenoid. Once the relay moves, however, power from 30 will flow to 87, activating whatever is beyond that, and at the same time flowing up through the diode to 86, latching the relay. So yes you're right. I misunderstood what you were saying before.

Basically means the relays are bog standard and he can test them on the bench.
 

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It’s not a latching relay! It’s a latching circuit and why the are calling it a latching relay because technically it is latching. Follow the current flow through the external diode in circuit.
The relay as shown has an internal diode to catch the small flyback current from the relay solenoid.
 

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Ah you tree’d me there. So now that’s out of the way he should be looking for voltage at pin 86 when the lever is shuttled either forward or reverse. If it’s only a momentary blink and not holding that external diode could be shot. No blink or voltage at all then look at the F-N-R switch.
 
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