CK35 HST Ground location for power relay

Kilo69 · Oct 5, 2017

I'm having a starting issue with my 2009 CK35 HST.

I have it narrowed down to the 30A power relay not having any ground plane. If I manually ground it back to the battery the relay activates and the IP solenoid clicks over and tractor runs fine until shut off.

Anyone know where that wire ends up getting grounded? Just trying to save some time chasing it back.

Thanks in advance.

Kilo69 · Oct 6, 2017

After finding the grounds and cleaning them up i still have the same issue. I believe the display unit is supposed to momentarily drop one wire to ground enough to trigger the relay. However it does not. Also when I manually activate the display does not work. No tachometer etc.

I checked the key switch and all wires show 0 ohms when the key is moved to the various positions. I also bypass the key by wiring and still nothing. So it's either the actual display unit itself or something in the wiring to it. Testing to continue as the local dealer would have to order in the $150 display unit regardless. But he really wants to sell me the $100 key switch. I'm not sure that is my issue though. I have had it apart and cleaned it up already during this.

xcgreene · Oct 6, 2017

Bypass the start terminals will tell you if the switch is bad or not. Good work so far with troubleshooting. What about the preheat control, that could cause you starting issues. Perhaps this will help, its a screenshot of the wire diagram from a CK 25, 30. I'm not sure what the differences will be for your CK35, but maybe it will be useful.

Kilo69 · Oct 6, 2017

I disconnected the wiring harness from the switch, wired across for power and still not engerizing the relay to open the Start/stop solenoid. Also noticed the auto glow plug cycle does not run but manual plugs do activate the relay.

Thanks for that diagram it seems similar to what I'm seeing!

xcgreene · Oct 6, 2017

you may have already tried this, but I thought I would mention for any others troubleshooting, be sure to connect the AM, M, and ST terminals in the switch harness to properly simulate the normal situation of start.

I know the switch is a bit expensive, but it would sure be nice to have a spare on hand, should you purchase one and its not the problem.

Just a thought, is there a switch for the gearbox range stick? I see in the wire diagram one for the clutch (assuming the diagram I have here is not for the HST model) perhaps there is one for the range stick that is out.

ritcheyvs · Oct 7, 2017

On your model (I think) the Display Unit provides the +12v signal to energize the glow relay and the ground signal to briefly energize the relay for the "pull" coil on the stop solenoid. The pull coil only needs to be powered for about one second. After that, the "hold" coil, which is powered directly from the key switch, keeps the stop solenoid retracted (engine run position) until the key is turned to the off position. The display unit had its own ground which provides that ground for the pull relay and display unit functions. The display unit also runs the tachometer.

Given that the tach and auto glow don't work either, I think the display unit (or wires to it) must be the problem.

By the way, do not apply power to the pull coil for long periods or you will damage the stop solenoid.

ritcheyvs · Oct 7, 2017

Kilo: I sent you a private message,

Kilo69 · Oct 8, 2017

Bench tested the display unit and it was working. 8 sec GP lamp and 15 sec on GP relay. Put it back in tractor and it worked once. Then never again even on the bench. Going to order another one. Checked wires and everything had continuity where it should have. Even popped open the display unit. Which looks just to be an atmel microprocessor. I have another atmel laying around I could likely program to make work. But would take a lot of time vs ordering a new one haha.

Thanks to all for your input and diagrams it was a huge help. Will update when the new display unit comes in.

For now I can use he tractor with a push button to ground the start stop solenoid relay. No tachometer or hour meter though. But tractor working is more important!