Volvo L70B raised servo pressure.

[Kelly Mehling]

Could someone with some experience with the L70 loader PLEASE try to help. I cannot get the "raised servo pressure" to shut off. I have checked the switch and the switch is working. However I can't find the solenoid that corresponds with that switch. The service manual shows it under the hatch at the front end of the loader, but I have been all over it, and it is not there. I know you're thinking, "it shouldn't be that hard to find the valve" but I cannot find the valve that the service manual is referencing.

Thanks.

 

[Volvomad]

What do u mean by raised servo pressure ? The switch to assist with quick hitch operation ? With C series most increased standby pressure issues are brake charging circuit problems.

 

[Kelly Mehling]

Thanks for the reply.
The manual calls the switch "raised servo pressure". I believe it is because the quick attach runs off of a low pressure feed, and the switch allows you to boost the pressure to the quick attach in the even the quick attach is bound up or sticking. But it is supposed to be only momentary, as the switch is spring loaded and will not allow the raised pressure to stay on. However, although my switch is returning, the raised pressure is not shutting down. I have tested the switch and it is working the way it should. That is why I think that the solenoid valve is sticking.

But I cant work on the solenoid valve if I can't find it.

My service manual says that the raised pressure switch ( SW-91) operates solenoid valve MA-48. But I don't have a MA-48 in the location the manual says, or anywhere for that matter. I feel dumb, but I cannot find that valve.

 

[sfrs4]

Interestingly everything on Prosis says it is a pressure draining solenoid? but also raised pressure attachment locking. I have attached the parts drawing showing the valve location, and also the wiring diagram for clarification. hope it helps

 

[Kelly Mehling]

sfrs4, thanks for that. Yup, I have those schematics in my service manual, so at least I know my manual is correct. From wiring diagram, switch 91 energizes solenoid 48.

now notice in parts schematic how the solenoid valves (item 34 and 15) are double ended, in other words the valve body has a solenoid on top and on bottom. I don’t have that. In my compartment I only have two solenoids. And my solenoids are labeled on the harness as MA 41 and MA 51, One is the quick coupler, the other is the floating function.

my serial number is 10922, so my machine should fall under both those schematics….

I’m confused…..

 

[Kelly Mehling]

So I looked at the wiring schematic for the later serial number and there doesn’t seem to be a MA 48 valve. Is it possible that my loader wasn’t equipped with that valve? If that’s the case, how does the switch raise pressure for the quick coupler system? From what I see, in the later system, the switch only deactivates the brake charging circuit

 

[funwithfuel]

The solenoid should be ganged up on the diff lock solenoid. I have attached the hydro schematic and legend.
When you open the front cover, with the boom safely supported! You'll see a pair or three blue cap vickers valves. You're looking there. I cannot remember exactly which for the life of me. Each stem should have a plunger accessible without disturbing the magnet. You can exercise the valve by simply spraying with penetrating oil and depressing the plunger several times to dislodge any debris or work free. If the mag has failed, you can swap for the neighboring, ie diff lock or return to dig.
Good luck.

 

[Kelly Mehling]

I would agree based on all the cited information provided here that it should be there but it’s not there. I have checked the numbers on all the solenoid harness wires and it’s not there.

and the raised pressure function worked as it should until just a few days ago, so I know the switch connects to something

I want to fix it, but in the short term I need someone to tell me if I can use the loader without damaging something.

 

[funwithfuel]

You won't be able to do any work, the valve is gonna rob all your pilot oil. It'll be like you locked out the pilot circuit, especially regarding boom function.
Can you attach a pic of the front area surrounding the main control? You might have something of a different generation anything really with a machine that old.

 

[Kelly Mehling]

Ok, I actually have all my other functions, so I don’t know if maybe the valve is kinda stuck halfway or what. But I can tell just from the sound of the hydraulics that there is an increased load that is not as usual.

If I can get time I’ll try to take a pic, but we’re in the middle of a snowstorm and I’m tied up trying to take care of cattle

 

[Kelly Mehling]

Honestly, I’m leaning toward the possibility that this machine is set up like the later serial numbers, and if that’s the case, I’m gonna have to have someone explain what the switch triggers to make the function work…

 

[Volvomad]

Can you hear the brake charge system working? Cutting in and out?

 

[Kelly Mehling]

No, I don't hear anything cycling so to speak. What I hear is more of general hydraulic noise, I guess you would call it a slight hissing, as well as the indication of some power robbing, that's my best description.

I didn't always use the raised pressure feature. Usually i would use it if there something kinda binding the quick attach, like an uneven surface when dropping the bucket. I would just bump the switch and the pin indicators would move more quickly as well as you could hear the additional load on the hydraulic system. Then all the sudden it didn't go off when I let the switch go back to normal. Dont get me wrong, the quick attach works really fast now, but I don't like that there is always that load on the system.

 

[FERG87]

I have a L70B with a similar problem. I have no power going to SW92, I have power going to SW91 and when you flip that switch the motor changes sounds. This is an older machine and it been put through the ringer. I have been looking at the schematics you have posted and have helped me out a lot but wires that feed off Fuse 14 when I pull the fuse it doesnt cut the power to the wires that it feeds off. Volvo sent me a diode and I'm assuming is is for D33 but I dont have power on either side of the diode. Any thoughts?

 

[sfrs4]

ok so i just revisited the wiring schematics, there are three slightly different ones by the looks of it, all down to serial number, so the one above, and these two below, hope it helps in some way