NH L220 Interlocks Have Me Defeated

Since it appears that Winter is finally over in upstate NY, I felt it was safe to remove my snow plow the other day. So, my SS started up just fine, shut the door, engaged my "seat belt defeat" switch (has a seat belt in place of lap bar), pressed the "operate" button on the panel, & WTF!!
The seat belt light is still blinking & the brake light is on steady, & of course all hydraulic functions are locked out because of this!!
After appropriate cursing, I removed the snow plow the hard way (with my FEL) & set about to try to diagnose the "locked" interlocks.

• Checked fuses - all OK.
• Buckled seat belt, thinking maybe my "defeat switch" was bad - no change.
• Unplugged seat belt interlock from the main harness behind the seat (uses a std. SAE plug), plugged in a SAE plug & pigtail into the harness, & positively closed the seat belt harness circuit (just like my "defeat" switch does) - no change. Just previously continuity tested the SAE plug & pigtail & it was fine.
• Decided that I needed to tilt the cab forward to check plug connections & such underneath. But the cab hold-down nuts are blocked by the vertical lift arms.
• So, tried to manually raise the lift arms with my FEL, but can't because the hydraulics are locked. The "emergency" hydraulic release in the cab appears to only work for lowering the lift arms, not for allowing them to raise.

In frustration, called my local NH service mgr., who suggested all the things I've already tried. Also, confirmed that the "emergency" hydraulic release usually only works to lower the lift arms, & even at that has to be held in position during the entire movement. So, even if it worked to allow the arms to be raised, it would be a 2 person job (one in the cab, another operating the manually-raise machine.
He suggested relieving the arm hydraulic pressure by cracking open one of the hydraulic connections on the lift are cylinders. Having checked them out, I see that they are all on the back side of the cylinders, not real easy to get at.

So, before I attempt what promises to be a very messy & knuckle-busting task of cracking open one of the hydraulic fittings, does ANYONE have any ideas!!!

By the way, have I mentioned how much I hate all the idiot interlocks on modern machines!!

The interlock's suck have for a long time. Provide another opportunity for system failure and in my view near zero benefit. I can only assume that they are "legal team" adds due to lawsuits filed but who knows, could simply preventing of lawsuits.

MY NH is old so I don't know if yours is the same or not but have you checked out the seat pressure switch?

Wow good luck finding the answers...would corporate help, or the company facebook? I will check for you....

StumpyWally said:

Since it appears that Winter is finally over in upstate NY, I felt it was safe to remove my snow plow the other day. So, my SS started up just fine, shut the door, engaged my "seat belt defeat" switch (has a seat belt in place of lap bar), pressed the "operate" button on the panel, & WTF!!
The seat belt light is still blinking & the brake light is on steady, & of course all hydraulic functions are locked out because of this!!
After appropriate cursing, I removed the snow plow the hard way (with my FEL) & set about to try to diagnose the "locked" interlocks.

• Checked fuses - all OK.
• Buckled seat belt, thinking maybe my "defeat switch" was bad - no change.
• Unplugged seat belt interlock from the main harness behind the seat (uses a std. SAE plug), plugged in a SAE plug & pigtail into the harness, & positively closed the seat belt harness circuit (just like my "defeat" switch does) - no change. Just previously continuity tested the SAE plug & pigtail & it was fine.
• Decided that I needed to tilt the cab forward to check plug connections & such underneath. But the cab hold-down nuts are blocked by the vertical lift arms.
• So, tried to manually raise the lift arms with my FEL, but can't because the hydraulics are locked. The "emergency" hydraulic release in the cab appears to only work for lowering the lift arms, not for allowing them to raise.

In frustration, called my local NH service mgr., who suggested all the things I've already tried. Also, confirmed that the "emergency" hydraulic release usually only works to lower the lift arms, & even at that has to be held in position during the entire movement. So, even if it worked to allow the arms to be raised, it would be a 2 person job (one in the cab, another operating the manually-raise machine.
He suggested relieving the arm hydraulic pressure by cracking open one of the hydraulic connections on the lift are cylinders. Having checked them out, I see that they are all on the back side of the cylinders, not real easy to get at.

So, before I attempt what promises to be a very messy & knuckle-busting task of cracking open one of the hydraulic fittings, does ANYONE have any ideas!!!

By the way, have I mentioned how much I hate all the idiot interlocks on modern machines!!

Click to expand...

Have you tried jacking up the machine and put some wood block under the bucket quick attach and pull the cable to get the loader to go up a bit to access the cab nuts .Make sure you take the door off before you do .You might have to put a jack under the rear of the machine to counter the weight of the machine to get movement to start .A little work but a lot less messier than cracking hydraulic lines .
What is serial number on your machine ? So I see how yours is set up .I can also send you a service manual in pdf form if you like .

Tool_King:

s/n of my machine is in my signature at the bottom of my post...

I would appreciate a PDF service manual...I have a partial copy now...I'll send you a PM with my email.

You mentioned "...and pull the cable to get the loader to go up a bit to access the cab nuts." What cable?? You mean the emergency hydraulic release knob in the cab?? As I mentioned, I've been told that this only works to release pressure to lower the arms...

And what do your mean by "... .You might have to put a jack under the rear of the machine to counter the weight of the machine to get movement to start." Seems to me if I lift the front of the machine, tilting it back, then put blocks under the quick attach, then lower the weight of the machine onto the blocks, what good does jacking up the back of the machine do?? Maybe transferring more of the weight of the machine to the front blocks, thereby putting more up-pressure on the lift arms. Maybe I just answered my own question...

Tool_King...I've rec'd the manuals you've sent...thank you VERY much. One or 2 I already had some version of, but your really rounded out my collection!! I should mention that I never had a service manual for my Ford 1320 tractor, because I've never needed it!! That machine is the epitome of reliability!!! Very close in reliability is my EH80 ex. Far below those 2 is my L220 skid steer, which seems to go bad just sitting doing nothing!!!

Anyway, I'll call you on your cell as you suggested soon....I'm currently fighting a summer cold...

Interlock issues can be interesting to say the least.
The New Holland are the same as the Case skid steers, with some minor differences.

If you need to raise the loader arms, power on the dash, and just press the ride control and float buttons, then lift with whatever you like. (I usually just tape the switches on and lift the loader arm with my crane)

This series of machine was prone to harness issues, and corrosion. A quick check of the fuse panel may show a relay with burnt pins.

There is also 4 diodes inline in the harness on the left side under the cab. These are very prone to corrosion, and failing. I would start here personally. (and yes, one diode is for the seat switch) You can simply jump the wires together for testing purposes, to see if your issue is resolved. The diodes plug into a 2 pin bullet connector, very similar to trailer wiring.
https://www.globalpc.co.nz/Electron...ads-Adaptors/Product-Specification-M8610.aspx

Some machines also had extra fuses at the rear left of the machine. These are ground fuses, for the relays and such.

GaryHoff said:

If you need to raise the loader arms, power on the dash, and just press the ride control and float buttons, then lift with whatever you like. (I usually just tape the switches on and lift the loader arm with my crane)

Click to expand...

You're the man, Gary!! In my case, I found that just pressing & holding the ride control button on the right joystick (with the engine running) was the trick to de-pressure the lift arm hydraulics & allow the lift arms to be lifted manually with my excavator!!

One has to wonder why this trick is NOT included in the service manual, or was NOT suggested by my dealer's service manager??

Now, I have the cab tilted forward (lift arms locked all the way up) exposing the "guts", so I will start trying your other suggestions on finding my interlock problem. Stay tuned...

So, Gary...
I was able to locate 3 diodes in-line in the harness on left side under the cab. I can't find a 4th in line...Where is it?? Here is a photo of the 3 harness plugs after I unplugged & removed the 3 diodes:


Looking at the electrical info in the Service Manual, I believe I've identified these 3 as:
My #...... Name...................Component ID........Wire Colors
1..........EH Seat SW UCM.........V-009...............yellow-yellow
2..........EH Lap Bar/Seat Belt...V-005...............yellow-yellow
3..........EH UCM Wakeup..........V-006...............yellow-orange

All 3 diodes have NO markings on them, they look identical, & do NOT look corroded in any way. Diodes being essentially electrical check valves, allowing current flow in only one direction, I tested each of the 3 by hooking them to a slightly used 9v battery & checked the voltage with my multi-meter, with results as follows:
My #............Voltage One Direction........Voltage Other Direction
1...............7.58v........................0.039v
2...............7.57v........................0.028v
3...............7.58v........................0.041v
The diode test procedure in the Service Manual is as follows:

My old multimeter does NOT have a "diode test" setting, so I'm a little perplexed as to how to interpret my test results. It seems to me that in my tests the "Voltage Other Direction" should have been 0.000, but maybe my meter is just inaccurate at low voltage. Should I just short each of the 3 diode plugs in turn in the harness for testing??
Then, if one or more of the diodes turns out to be the problem, how do I find a replacement?? I've looked in the on-line parts catalogs for NH L220 skid steers, & I can NOT find ANY diodes!! Fuses & relays, yes, but NO diodes. I will call my dealer's parts dept. & ask.

Update...Called my dealer's parts dept., found that the diode part info is as follows:

• Part # L71879, cost $9.80
• The only place it appears in the parts catalog is in the "Initial Stocking List of Parts".
• Rating is 400v, 3A

I will mention that getting to these diodes & removing them is a bitch!! What a dumb-ass place to put them!! The steps I had to go thru were roughly as follows:

1. Cab tilted up & locked.
2. From the right side, climb up & lay across the chassis compartment, with your head/eyes tucked just under the metal floor plate of the cab along the left side of the chassis. Look behind the operating linkage for the lift arm locks.
3. The pig-tail on the sockets are so short that you can hardly get your fingers to grip the socket to pull the diode plug out. In fact, mine were so tight that I had to use the fine pin noses of a snap-ring pliers & operate it in reverse to force the diode plugs out.

Whether or not any of these diodes turn out to be my problem, when I replace them I'm thinking of extending the sockets on the harness with a std. SAE extension cable so the diodes are more accessible in the future.

The fourth diode is about 6" ahead of the other 3 diodes. Has red or orange wires.
You can just short the diode plugs for testing purposes.
Also make sure you have power at the diode plugs.
Do you have power at the seat belt safety switch?

There is also some ground bolts to the frame under the cab. (fairly obvious locations) Perhaps they are corroded? Probably worth having a look at.

Gary....First, answers to your questions:

• Each of the 3 diode plugs DOES have power, as follows (measured across the wires in the same direction for each):
  • V-005 Lap Bar/Seat Belt 6.58v
  • V-006 UCM Wakeup 14.16v
  • V-009 Seat SW UCM -13.56v

• Yes, I have power across the seat belt safety switch wires, measured at the wire socket behind the seat. It measured about 3 to 4 volts, although I'm a little puzzled as to why it is so much less than the 6.58v measured in the same circuit at the extension socket of the diode V-005.
• The ground bolts to the frame under the cab are NOT corroded or rusted in any way. They look like new!!

With cab up, motor running, door open, & the panel showing a blinking red seat belt light & a solid red brake light, I pulled the diode from the end of each extension cable socket shown in the photo above, & shorted across the socket, in-turn for each of the 3. There was NEVER any change in the blinking red seat belt light or the solid red brake light. The only change was when I shorted V-009, then a yellow exclamation mark appeared, accompanied by a constant beep-beep-beep.

So, it appears to me that none of those 3 diodes is the problem. But neither did I find the 4th diode you keep mentioning. Here is a photo of the 3 diode sockets at the main harness, where I plugged in the extension cables.

Originally the sockets w/ diodes were outside the cable loom in the background & were wire-tied to it. You can see where I re-positioned the sockets along the loom of the harness coming toward the camera, plugged in the extension cables, & wire-tied the affair to the harness with 2 white wire ties.
You point out that the 4th diode is about 6" ahead of the other 3. That would put it almost at the bulkhead thru which the harness goes on its way to the fuse location. As you can see in the photo, there is no diode there, & I've felt/looked around very carefully. Unless the 4th diode is INSIDE the loom of the harness??? Do you know or suspect that to be the case??

The only other sockets I see are located on the back of the bulkhead behind your lower front legs, just behind the UCM, as shown circled in red in this photo:

I don't know what those are for, yet.

So, I'm still stumped...waiting to see if you have any more info or ideas!!!

Your diodes appear to be in good condition, unlike these ones:
https://www.heavyequipmentforums.com/threads/new-holland-l223.72081/#post-752196

Your lap bar/seat belt wiring is low on power (V-005 Lap Bar/Seat Belt 6.58v) and is your issue.
Should be at least 12V. I'm assuming you were checking the powers with the engine running or battery charger on.

Picture 3, is just extra plug ins on the harness, just for options your machine doesn't have.

Please perform the following tests,

(1)Place one lead at a good frame ground, and the other lead at
seat belt safety switch, connector S-043, wire RD 316
Should have 12V. Advise on results

(2)Place one lead at a good frame ground, and the other lead at
Fuse F11, (5 amp fuse) un-switched battery power
Should have 12V. Advise on results

(3)Place one lead at a good frame ground, and the other lead at
Instrument cluster connector A-001, pin 3, wire YE313 (you may have to back probe the wire)
Should have 12V. Advise on results.

Gary...I hope to get to the tests you suggest tomorrow...thank you.

In the meantime, I FINALLY found the 4th diode, about 8" back (toward the engine) not ahead, of the other 3. It comes out of the same loom as the other 3, & mine was wire-tied to the backside of the loom, which is squeezed tight up against the chassis. Here is a photo of how it looks as I found it:

...and here is a view at it looking forward along the loom after I cut the wire tie:

To get it unplugged & an extension cable plugged in, I think I'm going to have to un-couple some of the big plugs in the wire harness & get "medieval" with the harness in order to get enough room for my hands. How do you do it??

Sorry for the poor location instructions of the diode, but glad you found it.

The diode is in a very tight location, and is difficult to access. The harness plugs are always difficult to un-couple. It seems they almost seize together. If I need to repair the diode connector, I usually remove a few harness plugs, peel back the harness loom some, and the diode lead can go under the harness and pulled back a bit. Not a easy task by any means. If I remember correctly, this diode is for the main power relay, so you probably don't have to worry about this one.
You can usually pull the diode under the harness to remove and check the diode.

Gary...I did NOT get to it today, for sure tomorrow...
But you said that " (3) Place one lead at a good frame ground, and the other lead at Instrument cluster connector A-001, pin 3, wire YE313 (you may have to back probe the wire)."
It seems you want me to loosen the instrument cluster from the right hand column & probe pin 3 on the back side...Is that correct??

Yes, you will have to remove the mounting bolts for the instrument cluster, to access the connector on the back side.

Low volts to the lap bar/seat belt switch is your issue, just testing for power along its route.

Gary...Here are the test results (engine NOT running):
1. Frame ground to connector S-043, wire RD 316, seat belt safety switch - 4.75v (should be 12v, PROBLEM)
2. Frame ground to fuse F11 (5 amp) hot pin, unswitched battery power - 13.14v, OK.
3. Connector X-C23 (A-001) instrument cluster to cab, pin 3, wire RD 313 (not YE), unswitched power - 13.14v, OK.

Taking the panel out was a piece of cake, had to unplug the harness from the panel & probe the pin 3 connector hole in the harness plug. I should note that the actual pins on the plug are the exact REVERSE of what's shown in the service manual, i.e., pin 1 is at the upper right rather than the upper left as shown below in a photo from the manual:

I verified that I was probing pin 3, unswitched power, by pulling fuse F11, then voltage on pin 3 was 0.0 as you would expect.
So, back to my problem...why is the voltage low (< 12v) at the seat belt safety switch??? Where do I start looking?? Ideas??

Please do one more test:

(1)Place one lead at a good frame ground, and the other lead at
seat switch, connector S-002, wire 315RD
Should have 12V. Advise on results

If you have 12V at the above test, your issue is at the splice pack SP-012. It is a ultrasonic splice in the harness, so you will likely not find it easily. I have seen where the splice fails, and only a strand or so of wire is left connecting.

The fastest repair is to splice into {wire 315RD at seat switch connector S-002}, and run it to {wire 316RD at seat belt connector S-043). This is ok to do, because they are both powered from wire 313 (essentially all you are doing is moving the splice to a different location)



** I wouldn't worry about wire 313 being a different color, as you have verified that was the correct wire with your test. The schematic could be wrong, or could be a Case vs New Holland difference. Likely a schematic issue, as they have updated these schematics at least 4 times that I know of.**