753 Aux Hydraulics lights and button not working

So I have a 1991?? 753 with BOSS control, that I have had for 15+yrs. The Aux Hydraulics are not working like they should. The Aux Hydraulic Button and lights do not work and change form key start to key start. Sometimes I have no lights, sometimes one, and sometimes two, but one thing is always the same, and that is that the button on the Aux Hydraulic control does not make a change.
It used to activate the Aux, and one light would work, push a 2nd time, and it would lock on. I use it with the backhoe attachment and brush shredder I use.
no mater what the light, I can open and close my grapple but switching seems off based on the sound of the flow. It works but not like it should.
I have checked the control buttons on levers and they are good. The actuate the control solenoids on the valve body.
I think the Aux Control Module PN 6671669 Was 6669529 may be bad.
One corner seems to be bulging out like the potting material has pulled free and let water in???
Does my issue sound like a bad Aux Control Module or should I look at something else?
Is there anyone that I can send it to to test before I buy a new one for $600 or used for $300.
I would even consider buying one, that I could return for a restock fee if not to bad.
Any testing or suggestions are welcome.

Thanks

When my aux hydr controls stopped working, I was convinced I needed the module….but I found one handle harness was connected to the wrong mate under seat, and chewed wires at the module. So my advice is to very carefully inspect all wires first, upper left panel, upper right panel, under seat both handles and control module harnesses, solenoids for aux hydr activation. I spent hours looking at the wiring diagram in the service manual. That's how I found the mismatched handle connector. Bobcat service tech connected it to wrong mate.

Look on eBay for isocell. They may test for a fee. They rebuild many bobcat modules.

I do have the service manual, and I ohm'ed out every wire and check all grounds and even the in-line diodes. All checked good. It worked a while back and nothing has been unplugged. I also looked for rubbing or worn wires. No bare spots found. It is the lights and the switch not working, when it did before that has me thinking the module.. thanks for the suggestions.. iwill look at the Ebay site you suggestions.

Markle said:

Look on eBay for isocell. They may test for a fee. They rebuild many bobcat modules.

Click to expand...

Can you double check the name isocell? Can't seem to find it on eBay.

Here is the website:

Replaced the Aux Control Module, and issue is fixed. I think i will rebuild the Drive Motors, and it should run like a 30yr/old new one..lol. $613 w/shipping and tax. Thanks everyone for the suggestions!

After I installed the Aux Control Module, I could tell the solenoids were working but I did not have the grapple on to test the system. Now I have done that, I still do not have correct flow and pressure like I should. I will add that my drive motors, lift and tilt are working fine and have plenty of power. I did a check to make sure the cylinders on my grapple were not leaking past the packing, and it was good. I could disconnect the quick connections from the bobcat with the retracted or extended, and the cylinder is hard locked and will not move up or down. I did this for both cylinders in case one was blown causing a blow by issue. My grapple cylinders are in good condition. I also checked to see if I got fluid flow from each hose when I triggered the buttons on the handle, very quickly, and both hoses shot fluid at high pressure for 15+ feet. I have not done a pressure test yet, as I don't have a hose and flow control valve set up, and I am pretty sure Bobcat won't rent theirs…lol
Given how my lift, tilt and drive work, I don't think my issue is with my pump. I think it is a valving issue.
For my first test, I isolated the system by connecting the hoses from the quick connect direct to only one cylinder and here is what I observed.
When I connected the bottom connector on the Bobcat to the top of the cylinder, I could actuate it up and down, although it did so very slowly, and with the button not actuated, it seemed to drift down. I could even push it down manually by just putting weight on it. Then I reversed the connectors on the cylinder, and it would not move. The hose would energize, and you could see them flex, but the cylinder would not move.
I have two ideals, and I am looking for help or input on a direction. (See Videos One works and one doesn't work)
1. The rear auxiliary valve has two check valves that probably have to work together to allow one side to release while the other one holds pressure based on which solenoid is energized for the auxiliary circuit on the main hydraulic control valve body. One of those check valves may be blocked or bad. (Ref Items #4 on Rear Auxiliary Valve Diagram) Check Valve-6664212 - $158ea +tax
2. The Solenoid valves or Spool in the main hydraulic control valve body. Maybe they are stuck or clogged? Solenoid Vale- 6653395 – $505ea.+tax
I am open to any input on what I should look at next.
Thanks