John Deere 690D LC System Controller Mode not working

[S.Moore]

Hello, the problem I'm experiencing is very similar to the issue that was being discussed in this thread.


I just purchased a John Deere 690DLC Excavator that has an issue operating when under control of the system controller. It works useable with the computer control bypass switch on. When in computer control mode it will work properly for a few minutes before idling down to low idle and engine speed control becomes unresponsive. If I push the "I" (Idle) mode button, the hydraulics work about like they should for being in idle. The three other modes have little to no hydraulics at all. (swash plate responding to system controller but not throttle perhaps?)

When I run the computer's self diagnostic by pressing the button on the controller, I am able to test and adjust the low Idle speed. When I press the button again to proceed to the high idle check, the system controller revs the engine up to high idle for a minute or two before idling down and throttle becoming unresponsive. All the lights and buttons on the console appear to work normal, but no change in throttle speed. If I shut the engine off, throttle speed will work again, until I go to high idle for a few minutes, then back to original issue. In the time when the throttle is working under computer control, the excavator works great in all modes.

Reading the forums here I suspected the engine speed sensor. However, it tests good according to the technical manual (TM1508) as far as ohms go anyway. Next I tested the engine speed control actuator solenoid. The tech manual says it should read 26 ohms, my meter reads 6 ohms. I'm thinking that this solenoid is failing as when it throttles up. As more power is fed to the solenoid, it gets hot and too weak to maintain pushing force on the hydraulic speed control valve. This sounds like a great place to start replacing parts, except John Deere and everyone else wants over $1200 for this little thing. It's hard to spend that when I'm not 100% sure that'll be the thing that fixes it.

I did order a similar solenoid off eBay for $120. It is the same manufacturer (Magnet-Schultz), throw (2mm), size (35mmx35mm), bolt pattern, voltage (24v), only difference I can spot is the mating surface lacks the o-ring groove of the original. I'm betting I can make it work.

Any thoughts or comments?

The excavator's serial no is 565900
I have TM1508, Operation and Tests manual
All fuses are tested good
I have not yet tested any other sensors/solenoids/relays other than the engine speed sensor and throttle solenoid.

-SM

 

[mg2361]

I have TM1508, Operation and Tests manual

That manual is for a 690"E". Do you have an "E" or a "D"? They have different throttle control solenoids.

When in "P" mode and engine rpm drops, does the light stay in "P" or does the light change to one of the other modes?

Check your system voltage during proper operation and when issue occurs and post.

 

[S.Moore]

It is a 690E LC, not "D" I had a 690D previously, force of habit. I don't see a way to edit the original post though, unfortunately.

I'll observe the mode and system voltage today and report back.

 

[S.Moore]

System voltage, measured at the in-cab light bulb connection is 27.41v before the loss of throttle issue and 27.35v after. To test, I start engine, put in "P" mode and operate about 2 minutes until the machine throttles back to idle while in use (not auto idle). The power setting remains in "P", it does not change on it's own.

On another note, I tested the pump control solenoid and it reads 26 ohms as indicated in the manual. This solenoid looks identical to the engine throttle control solenoid that's supposed to test 26 ohms but only tests 6 ohms. Evidence is pointing to that engine throttle solenoid more and more.

 

[mg2361]

Evidence is pointing to that engine throttle solenoid more and more.

I agree. If your light is not changing from "P" that usually indicates a solenoid/solenoid wiring issue.

 

[S.Moore]

Just got the solenoid installed today. So far that seems to have fixed it. I ended up buying the OEM solenoid from John Deere after all. The one that I got off ebay was close, but the pin was about 5 mm shorter.

Thank you all for your help!

 

[mg2361]

Always nice to hear a success story. Happy digging and Happy Thanksgiving!

 

[jimrr]

First posting here: I hope this is a appropriate thread? I'm working on the neighbors 690 EL #552582
TM 1508 (july 2019) system controller light check step 1: push the button and observe lights. "does light 1 come on red, change to green and go out?" NO!
It stays on red. according to the book the cure is to replace the controller. Is this always the case, is there any way it could be something else?
I have read every thread over the course of a week before replying. This machine's issue is it won't travel unless the boom/bucket are operated simultaneously and I do have a idea where to start on this but not getting past step one on the system controller checkout bothers me.
Thx, Jim