Odd Electrical Problem?

Hello!

New owner of used Bronco (13AJ609G766) with weird problem...

When I first brought the mower home, it wouldn't run unless I had either the brake or the gas pedal pressed slightly. With the key in any position, drive in neutral, the motor would cut out if I didn't have my foot on either the brake or gas. (This might be by design? I can't find a reference to it anywhere in the manual)

After a few uses, though, the motor would cut out badly... every 10 feet or so, it would pop or backfire as though the ignition was being intermittently disconnected. On a hunch I put a little pressure on the brake: lo and behold, no more cutting out! So as a temporary measure I disconnected the brake (at the rear pulley) and wired the brake pedal so it's always "braking". That fixed it for a while.

Now it's started to do it again, no idea why... It will idle fine, has plenty of power, moves around properly and the stupid reverse switch thing works properly but it's cutting out just like it did before.

Maybe this isn't the way to fix the issue but: is there any way to just disable all that electrical crap? It would be great if I could just turn the key, engage the PTO and go!

TheRiflesSpiral said:

Hello!

New owner of used Bronco (13AJ609G766) with weird problem...

When I first brought the mower home, it wouldn't run unless I had either the brake or the gas pedal pressed slightly. With the key in any position, drive in neutral, the motor would cut out if I didn't have my foot on either the brake or gas. (This might be by design? I can't find a reference to it anywhere in the manual)

After a few uses, though, the motor would cut out badly... every 10 feet or so, it would pop or backfire as though the ignition was being intermittently disconnected. On a hunch I put a little pressure on the brake: lo and behold, no more cutting out! So as a temporary measure I disconnected the brake (at the rear pulley) and wired the brake pedal so it's always "braking". That fixed it for a while.

Now it's started to do it again, no idea why... It will idle fine, has plenty of power, moves around properly and the stupid reverse switch thing works properly but it's cutting out just like it did before.

Maybe this isn't the way to fix the issue but: is there any way to just disable all that electrical crap? It would be great if I could just turn the key, engage the PTO and go!

Click to expand...

Not an odd problem at all. quite a common one.
There are 2 safety circuits designed to protect you and by standers that work in parallel.
1) brake + seat kills ignition :- In case you fall off
2) PTO + seat kills ignition :- so you can not shove your hand into the discharge cute when it is blocked.

There is a third switch, have no idea why it is there and that is the mow in reverse which will cut the ignition on manual PTO's or the deck clutch on electric PTO's.

Download your owners manual and parts book.
In one of them there will be a circuit diagram.

The switches are fairly cheap and suffer from dust ingression , corrosion & vibrational wear.
The wires to the switches suffer from vibrations and regularly break at the crimp terminal ( PIA to diagnose ).

If you have problems reading circuit diagrams ( like 90 % of the population ) get back to us and some one will explain it to you.

bertsmobile1 said:

Download your owners manual and parts book.
In one of them there will be a circuit diagram.

Click to expand...

Thanks for your response, Bert!

I was able to find the OM and a wiring diagram. No parts book as a download, but I can find parts on several websites so I think I'm good. Do you happen to know where I can get a shop manual for it?

I don't believe the seat switch is installed on this one; I've been off the seat several times without any engine cut-out so that might be my problem. (It wouldn't surprise me if the wires were just hanging somewhere and shorting on the frame or something.)

I'm going to trace the wires down this evening. Thanks again for your help!

TheRiflesSpiral said:

Thanks for your response, Bert!

I was able to find the OM and a wiring diagram. No parts book as a download, but I can find parts on several websites so I think I'm good. Do you happen to know where I can get a shop manual for it?

I don't believe the seat switch is installed on this one; I've been off the seat several times without any engine cut-out so that might be my problem. (It wouldn't surprise me if the wires were just hanging somewhere and shorting on the frame or something.)

I'm going to trace the wires down this evening. Thanks again for your help!

Click to expand...

AFAIK there is none specific to your mower.
However what you are looking for is an MTD 600 series manual.
The 700 series is all over the web and was close enough for me.
In fact for most techs an accurate parts book is all we need as basically all mowers are the same.
MTD put out a series of manuals in the 90's called the " Must Have Manual of Outdoor Power equipment" in 4 volumes
Volume 2 covers domestic ride ons and Volume 3 covers Garden Tractors . They are big books but that will have all the information you will need to work your way through mower repairs.
I think there s a copy on here http://www.mymowerparts.com/pdf/

Because wiring is fairly uniform there is a wonderful manual series put out by Toro called "the Demysterfication Guide" which also has proceedures for working your way through the "Mystery of Mower Wiring".

Unfortunately there is no common wiring colour code across the industry so colours get confusing.
Also to cut costs they use double switches on the PTO & the Parking brake and these switches come in 2 ways N/O + N/C and the opposite N/C + N/O and it is common to find a wrong switch fitted then bypassed when the owner could not get it to work properly.

The only big thing to worry about is accidentially sending voltage down the kill wire to the magneto that will fry the magneto.
Thus It is prudent to unplug the kill wire at the magneto while working through the wiring, then double check the kill wire is only ever open ( running ) or ground ( off )

Wow, thanks so much! Very helpful.

I was able to get the seat switch re-connected, the brake and PTO switches cleaned and functional and all seems well at this point.

The only weird thing I'm experiencing now is that any time I get out of the seat, the engine shuts off. PTO off, trans in neutral, parking brake on, if I close the seat switch, the engine dies. As far as I can tell from the user's manual, I should be able to leave the seat in that condition. Is that accurate?

Yes yo should be able to get off with the brake on and the engine remain running.
AS you can start the engine that suggests the brake switch is OK so you are looking at a dud seat switch or wiring between the seat & parking switches.

bertsmobile1 said:

...you are looking at a dud seat switch or wiring between the seat & parking switches.

Click to expand...

I did find some scuffed wires where the wiring loom had been rubbing on one of the drive belts. I'm guessing it's something in that vicinity.

Thanks again for all your help!