Need help accessing the clutch safety switch on a B7800

[TJIC]

I've owned a B7800 for 10 years. Bought used, now 1100 hours.

Recently it's gotten harder and harder to start - turning the key lights up the dash, and I hear a click of a relay, but no power to the starter. Jiggling the clutch pedal, the PTO controls, etc often gets it started ...after 2 / 3 / 4 tries ...but it's gotten worse. Now can't get it started at all.

I'm 99% sure that one of the safety switches is the problem.

I've taken off the panel under the seat, and used a multimeter to test both seat switches, both PTO safety switches, and the HST switch. All switches are good, but I jumpered them just to be sure.

The last switch is the clutch safety switch. I've located it, but assume [ perhaps incorrectly ] that I need to remove a body panel to access it. I've taken off the dash and just learned that the fuel tank is in the way. I started taking off the hood and removing the firewall, but I'm not convinced that this is the right approach.

How do I get access to the switch and the 2-wire connector to either jumper it for testing, or remove the switch to test it at the bench / replace it?

Thanks.

 

[85Hokie]

Have you tried moving in the seat, moving the PTO lever and moving the HST pedal as you turn the key?

The switches can all be good - but the closing of the circuit may be the problem - the pressure against the switch may be the problem

 

[TJIC]

Have you tried moving in the seat, moving the PTO lever and moving the HST pedal as you turn the key?

The switches can all be good - but the closing of the circuit may be the problem - the pressure against the switch may be the problem

Will give that a shot, thanks ... but even if that works, I still want a permanent SOLUTION.

I did adjust the linkage from the clutch pedal to the flange that pushes against the clutch safety switch to add extra throw.

 

[lugbolt]

I used to have a tool I made out of....a Kubota tractor crate....that worked fairly well to get the nut off of the B series clutch switch. Wasn't hard to make it, just some 3/16" plate with a slot cut into it that fits the nut, and bent so it'd fit up in there. I wanna say it's 27mm or 1 1/16" but it's been so long I may be wrong on the actual size. I might still have it in my tool box at work, as I do a couple Kubota's a year still (4 years after leaving the kubota dealer) for customers that won't go back "over there". I'll see if I can remember to look for it in a little bit.

 

[TJIC]

Hey @lugbolt, thanks for your answer!

To be clear - do you remove any body panels, or do you just access the safety switch from underneath/from the side? Access is tight that way, so I assumed it'd be easier if I took a body panel off, but maybe it's not totally impossible to just remove it without tearing things apart ...

 

[Henro]

I've owned a B7800 for 10 years. Bought used, now 1100 hours.

Recently it's gotten harder and harder to start - turning the key lights up the dash, and I hear a click of a relay, but no power to the starter. Jiggling the clutch pedal, the PTO controls, etc often gets it started ...after 2 / 3 / 4 tries ...but it's gotten worse. Now can't get it started at all.

I happen to have a B2910 which is the deluxe version of the B7800. I also have a BX2200.

You mention no power to the starter. But the reality probably is that the starter solenoid is not being energized and that you do have power sitting at the starter, but not being applied to the starter motor itself, because the starter solenoid is not operating magnetically strong enough to make the starter motor function.

This is a classic problem with older BX tractors. The solution is to install an interposing relay between the permissive circuit that operates the starter solenoid and the solenoid itself. It’s a very easy modification to make. What you do is use the wire coming from the permissive circuit that connects to the solenoid, and move it so that it operates the relay. Then you take 12 V that comes to the starter itself, run it through the Contacts of the relay and connected to the starter solenoid terminal.

The root problem is that resistance increases overtime across the safety, interlock switches, and eventually they drop enough voltage so that the starter solenoid does not get enough voltage applied to it, so it doesn’t produce enough magnetic force to activate itself.

I’m just throwing this out because what you’re describing exactly describes what went on with my BX, and after installing the relay I mentioned, the problem went away 100% and has not reappeared in probably three years now.

This is something to consider as a possible solution your problem. If I had a similar problem with my B2910, that’s what I would do first off.

 

[TJIC]

@Henro , great reply, thank you!

I swapped in a new starter a few weeks ago, on the theory that many folks have said that a 15-20 year old starter might be getting weak. I also did some testing to see if there was power on the low amperage starter wire, but I forget exactly what I learned. I THINK I learned that there was no power there, which is why I went down the safety switch route, but I can't be 100% certain. I'll do the test again!

...but also, I understand that you're saying "there would still be current / voltage, just not enough".

Let me investigate / think on this!

 

[lugbolt]

Hey @lugbolt, thanks for your answer!

To be clear - do you remove any body panels, or do you just access the safety switch from underneath/from the side? Access is tight that way, so I assumed it'd be easier if I took a body panel off, but maybe it's not totally impossible to just remove it without tearing things apart ...

no i had to take the panel out, and then the pedestal cover. It's still a bear but doable.

 

[TJIC]

ok great info @lugbolt , thank you!

"how to take the panel out?" was actually the original question. Got any particular words of wisdom? I haven't yet figured out how it's secured (it all looks so easy on youtube when Diesel Creek or one of those other guys just zips a machine apart in high speed time lapse! )