Just purchased this loader knowing it had no brakes,#8AJ01502,I was pretty sure I knew what was wrong,and so far so good.The peddles were froze solid.The pivot,rollers,and plunger were all a big ball of corrosion.and one air valve had a big groove under the o ring.So two new air valves,peddles and mount ass'y and the service brakes work perfect.My problem is the monitoring system still flashes.The code is,low hydraulic brake pressure.There is also a light for low air brake pressure that does NOT come on.The only pressure switch I can find on the hydraulic side is for overstroke of the master cylinders,and cannot find reference to repair, low hydraulic brake pressure in my service manual------ The brakes work great,I think I have bad pressure switch that I'm not seeing.Im working outside in the snow so maybe I'm not looking hard enough.
Checking the wiring diagram and there are two identical pressure switches on this machine. Part Number 9G8009. One is in the parking brake circuit. looks like it is mounted near the front of the transmission behind the front of the rear frame. It should have wires 201 Black and 419 Yellow. The other I would think is the one you need to find and it appears to be mounted to a TEE fitting on the left side of frame in the area of the center pins, not sure if it is the upper or lower center pin from the parts book drawing. It should have the following wires 201 Black and 408 White. Hope this is of some help. They are both #11 in this drawing
There is a switch on the air line TEE to the cyls, it controls the brake lights. The other one in the park brake line and controls the brake on warning so you don't drive through the brake and ruin it. I think your problem is the overstroke rods in the air cyl or the switch. The rods need to be reset by hand. Push them towards the pistons. Later Bob
A couple more pictures first one is from the wiring diagram showing the low air pressure switch and the stop light switch. Low air pressure switch is the 9G8009, Stoplight switch for brake lights is the 2M9346. This second is from the parts book shows the location of the stop light switch, # 18 in picture. Can not tell which side of the center pin on the rear frame it it but should be easy to tell if you check the wire colors and numbers in the upper image. Looks like it is mounted on the underside of the floor for the cab.
You can test each overstroke switch by connecting the two wires together on the switch on each of the master cylinders. If you test it this way it will tell you which switch is turning on the light. when you push the overstroke pin in make sure it is in all the way. The overstroke switch is just a ball that drops into a notch on the pin.
But make sure you put the wires back where they are supposed to be after you finish testing. I once had to do an accident enquiry into a 785B when it ran out of brakes (worn out and rotochambers overstroking) - we discovered that the 2 wires on 2 out of the 3 overstroke switches were wired on to the same terminal .......... guess which rotochambers were overstroking..? As Mobiltech points out, you have to reset those overstroke switches manually by pushing the pin inwards until you can feel it click as the spring-loaded ball drops into the groove on the pin, they do not reset themselves automatically. You may even have the groove in the pin so full of crap that the ball/spring are stuck in place and will not spring into the groove even if everything lines up. Possibly some additional disassembly required.
Problem solved! At least for now.Ont/Bob hit it in post #3.The bottom air/oil master cylinder(front brakes) at some point in the very distant past,had over stroked,and kicked the pin.As Nige said it did not want to reset,after some cleanup sanding and a little lube,got it to go home.All system lights are now off,worked the brakes hard,and still ok.---- Thanks again to all that helped out!----Now it's on to the tail lights and turn signals that don't work.
And sometimes you have to bite the bullet and replace the switch(s). Problem with the over-stroke switches, unlike most switches, is they will go for years ore even decades without ever being moved and when they do they are full of rust and corruption they will not reset even after cleaning as Nige says. I know you have cured the problem but would suggest you look over the pictures I posted and try to locate the three brake related switches for future reference. Then you can look smart by knowing right were they are located and what each one does
I did find them,when I replaced the brake air valves.I checked them with a meter.But they were on the air side,and my light was for low hydraulic pressure.The service manual for this machine is a little vague,on a lot of things.I did not associate the overstroke switch,with low hydraulic pressure.There are a lot of switches on this machine.---Again,thanks to all that have helped!