OEM Ignition Switch for ZD326 Worth the Extra $70+?

[Mr Haney]

I have been fiddling with my used ZD326, which refuses to start without hot-wiring.

I thought I had a bad relay. Switching relays did not fix the problem, so I moved down my list. I checked all remaining safety switches, and they were fine.

I went under the seat, disconnected the ignition switch plug, and tested for continuity between the red (hot) and black/yellow (start) wires with the key on "start." I got 300K ohms, which seems a tad high compared the ideal value of 0.

My question: is an OEM switch worth the extra money? Call it $100 after shipping and so on Chinese switches can be had for about $23.

I am going to pull the old switch and see if I can clean it up for now. I am hoping the switch really is the problem, because if it's not, it could be the controller. Before I would fool with that expensive part, I would start scraping grounds all over the mower.

 

[GreensvilleJay]

both switches might be made in China(seems 'everything' is...), so roll the dice on the $23 version.
If buying through Amazon and 23 doesn't work, send it back.....returns are free.

 

[Mr Haney]

You are probably right.

I took the switch apart. It didn't seem worn, but there was a lot of oxidation on the contacts. I cleaned them with De-Ox-Id and 800-grit paper and checked the resistance again. Close to 0 ohms.

Sadly, the tractor does not start, however.

 

[GreensvilleJay]

well it's only a 4 pronged switch, so not complicated. Hopefully you have the wiring diagram. It can't be too complicated.

 

[Mr Haney]

There is not much to it. You open it up, and there are bunch of copper contact surfaces. Seems to me either they conduct or they don't.

 

[GreensvilleJay]

jumper whatever wire has +12 from battery to the 'start' wire.....starter should spin. If not, follow the 'start' wire and see where it goes ?
I suspect there's some 'box' to decide that all the safety switches are in their correct place, making it more 'fun' to trouble shoot.

test.... jumper the starter to see if it spins... yes, then starter is good.

there's probably a 'starter relay'. if so , find it, check or swap with similar one.

 

[Mr Haney]

Yeah, I went through all that in addition to repairing the ignition switch. Safety switches good. Relays don't appear to be the problem. Starter is fine. It's looking like the $300+ controller will turn out to be bad. I will know more on Monday when the relays are replaced.

 

[lugbolt]

check the r/b wire. Do a voltage drop test between the key switch and the starter. If the drop is high, work your way back up the wire and drop test each component. Have seen relays fail this way, have seen combination box fail, have seen actual bad wire (corroded inside insulation). You have to test the system using a voltage drop test. Here is why. One strand of wire will test 0.0 ohm, but that single strand won't carry enough juice to engage a higher current device (solenoid in this case). But if you do a drop test, you'll find a significant drop between each end of that same conductor.

 

[Mr Haney]

Thanks for the tip about voltage drop.

I am posting a copy of the PDF page for the starting system. I am looking at it now and writing a long analysis.

That controller is a real jerk. It gets its nose into everything.

 

[MapleLeafFarmer]

My question: is an OEM switch worth the extra money? Call it $100 after shipping and so on Chinese switches can be had for about $23.

Not sure for lawnmower but around here for ag. tractors and construction equipment if non oem parts used or bad after market mods are noticed it becomes a harder sell and a very tough trade in.

Buyers can worry if say a cheap after market switch is used what about engine repair parts, filters, hoses, belts, etc...

If never planning to sell it's a non issue and strictly personal preference. Dealer or a private guy might get gun shy and drop price accordingly

 

[jaxs]

If it comes down to the $300 controller, before I bought a new one I'd try the Deox-it on old one. Looking at pictures it appears that housing is sealed. My first attempt would be drill holes in apposing sides to insert straw and spray then blow out with air hose. If that didn't bring it to life I'd use Dremel Tool to open housing for a look.

 

[Hugo Habicht]

I am posting a copy of the PDF page for the starting system. I am looking at it now and writing a long analysis.

That controller is a real jerk. It gets its nose into everything.

The controller is very useful, may save your butt if things go wrong. And it's not the controllers fault if it gets fed wrong signals. So please look at it a tiny bit more positively

The controller has no information about the start switch position (signal 50). The full starter solenoid current is only controlled by the switch and the starter relais (6). Hence the controller must activate the starter relais (6) only depending on safety switch positions. 5 switches, 4 controller inputs, easy to check the inputs at controller connector (measure voltages at the controller, not resistance of switches).

So check switch voltages at controller connector, toggle switches and make sure they all work. If not, adjust switching point mechanically (!) or repair / replace switches.

Then you check if starter relais (6) gets coil voltage. If not check for faulty wiring. If wiring good control box is faulty.

If starter relais (6) gets coil voltage and is active check for voltage on starter solenoid when turning start key to start position. If no voltage, check before starter relais (from switch). If no voltage there replace switch. If voltage there replace starter relais.

And as I said before: always measure voltages (against battery minus terminal), never measure resistance on cables or switches.

 

[Hugo Habicht]

Here the wiring:

red - 12V path for starter current to starter switch
yellow - starter solenoid current path from start switch via starter relais
purple - 12V path for safety switches
green - safety switch signals to controller

Also check ground connection of controller (blue). Measure voltage between battery plus terminal and the controller connector ground pin. When turning start key the voltage should always be 12ish Volts (will drop a good bit when pre glowing).

 

[jaxs]

Good on you Hugo for the work you put into that.

 

[Russell King]

@Mr Haney
The PURPLE and RED in the marked schematic are close in color so be careful when looking at the screen to notice the differenice!

At first glance they looked the same to me.

 

[CGMKCM]

Have you cleaned up the battery - to engine block connection? Sounds like that mower sat out in the weather if you are finding corrosion on contacts etc.

 

[Mr Haney]

Thanks for that help, Hugo.

Based on all the written analysis I did yesterday, it looks like the controller's only purposes are to shut off the engine and make the safety switches work, keeping lawyers away from Kubota's money. It appears to have nothing to do with running the engine or transmission, although I have seen claims that it controls everything.

I read about a mower on the web that had the ECM completely bypassed, so it is not actually needed to make the mower run properly. Correct me if I'm wrong.

I don't know why Kubota made the shut-off relay go through the controller. There must be some reason. I don't see why the mower needs to give you permission to shut it down.

The relays go in on Monday. The ECM ground will be checked. I'm treating the fuel. The new filters go in on Monday or Tuesday.

 

[Hugo Habicht]

Based on all the written analysis I did yesterday, it looks like the controller's only purposes are to shut off the engine and make the safety switches work, keeping lawyers away from Kubota's money. It appears to have nothing to do with running the engine or transmission, although I have seen claims that it controls everything.

I read about a mower on the web that had the ECM completely bypassed, so it is not actually needed to make the mower run properly. Correct me if I'm wrong.

I don't know why Kubota made the shut-off relay go through the controller. There must be some reason. I don't see why the mower needs to give you permission to shut it down.

Yes this is correct, the controller (as far as I can see in the schematics) is for safety reasons mainly. The engine could run without it if you bypass the safety switches or wire the starter relais (6) directly.

The shutoff relais is required to run through the controller to apply voltage to the shutoff solenoid for a specific period of time when you turn off the starter switch and also to be able to stop the engine when safety switches require it to do so.

On my lawn tractor the control box has similar functions. I initially laughed at the seat switch and also had bypassed the faulty brake switch. But when driving it I noticed that it is very easy to be thrown off the tractor and I don't think it would be funny watching your lawn mower driving away from you at full speed with blades rotating. Has not much to do with lawyers initially in my humble opinion.

So I repaired everything to work correctly and I would advise to do the same. As I said before, this controller may save your (or somebody elses) butt one day.

Apologies for the purple colour, not a good choice in hindsight, but both are connected to 12V anyway, just through different fuses.

 

[Mr Haney]

I appreciate the help. It is true the mower could throw a person off. I think I prefer the seat belt to the switch, though.

A customer who has been run over by his own mower would be a lawyer's dream.

 

[Hugo Habicht]

A customer who has been run over by his own mower would be a lawyer's dream.

While this is certainly true this lawyer would not be able to give me my foot back after it had been chopped to bits by the cutting deck. So therefore I prefer my working seat switch and control box to a lawyer.