I have a Bobcat 753 Serial# 508615824 It is equipped with a BOSS system. The display went bad already many years ago, but we just kept using it because everything was working OK. But now recently, my auxiliary hydraulic stopped working. The green LED on the switch would not turn on anymore. So I looked into it and saw that the LEDs were corroded away. So I bought new ones and soldered them on. After that, it was working again for maybe one hour but then the same thing happened again and it stopped working. Now it will only turn on for a second and then not anymore at all. So now I wanted to remove the entire BOSS system and replace the gauges with analog ones. This is pretty easy to do. My problem is the auxiliary hydraulic; I don’t really know how to bypass the BOSS system and the auxiliary control module to make it work again. Could I just energize the 3 solenoids in the hydraulic system (see pics) with 12 V to activate the auxiliary hydraulic? If so, I guess my turn on button and switch in the hand lever could also not be used anymore? Has anybody done this and has some experience? Thanks for any input. Pat
Due to lack of respond, I went ahead and tried to figure it out by myself. It was actually more easy than I thought. I only had to energize one of the two solenoids which are on the main hydraulic control valve, either one controls the flow in the other direction. For safety, I added on a simple on off switch in the other hand lever, so I can easily turn it on off. The solenoid in the rear auxiliary valve had to be disconnected. So all the fancy electronic hydraulic control could be eliminated. To eliminate the BOSS system, I used the relay for the glow plugs to energize the fuel shutoff valve when I turn the ignition key switch to on. I do not need glow plugs, cause we are in Hawaii. So now I’m just waiting for my water temperature, oil pressure, and fuel level gauges to be added to the new set up. RIP BOSS.
Well….. looks like I need to put a little bit more thought into it, I just burnt up my fuel shut off solenoid, lots of smoke. I thought I could just leave it energized, but obviously that does not work, so I order a new one and figure out something else. Some better ideas?
I also see my manual shows a fuel shot off solenoid timer module, which I cannot find on the machine. So I wonder if it’s not there maybe because it is incorporated in the BOSS system?
You can put power to the solenoid hold winding , but not to the pull winding as the coil in it will burn out. I may be wrong but am sure the pull winding is only good for lets say 15 seconds or less. It may run through a timer, could not tell without seeing the schematic. Simon C
Your solenoids may operate on less than 12 volts. Most run on 5 volts or less. Thats probably why they burned up.
To get around the timer style on my machine, I wired the pull in coil to the machine starter stud, therefore the pull in windings for the fuel solenoid only activates when cranking starter. Then the hold solenoid coil, is just wired to the run position on the key. Then pull in windings ohmed out at .4 and the hold solenoid coil ohmed out at .024.
On these single battery systems, if the battery does not have enough capacity it will pull the solenoid and continue cranking while the fuel solenoid drops out. Have repaired this on multiple generators that would crank but not start on 1 battery. With the second battery installed in parralel the solenoid never dropped out again. Poor connections in the solenoid circuit could cause it to drop out. A faulty , starting to ground out solenoid can cause the problem also, but usually cuts off a fuse first depending on how it is wired. Simon C
That is exactly what I was planning to do now. Just waiting to get my new solenoid. I was looking online afterwards and saw that one of the wires is for pulling it in and the other one is for holding. I didn’t know that before. Obviously it does run with 12 V pulling in and 5 V holding but on another forum somebody else said he wired it also like that with 12 V pulling in on the starter and 12 V holding on ignition switch on and was working fine since many years, so I will try the same and cross my fingers.
There is numerous types of those solenoids for many different applications. You really need to know what the required voltage is for the start and ignition side and make sure you have a solenoid that applies.
Or you can buy a cheapy Bobcat clone in Amazon for 20 bucks and try it. They have boat loads but no directions and no schematics. I just OHMed it out.
That's what I did; just I spent $30 on it.
I believe it will be 12 volt. You just smoked the pull coil. You're on the right track
So I got it back together; new solenoid works fine. Also installed the new gauges. The only problem is with the fuel gauge. It shows empty, even though the tank is full. I was hoping to just reuse the old sender in the tank, which I believe is still OK, but it seems not to communicate correctly with the gauge so I wonder if anybody knows what ohm range the original sender is working? Then I could try to find a corresponding gauge. I’m not sure if it’s possible to install the sender which came with my gauge, because the mount is a different style and also to remove the original sender from the tank without removing the drive pumps I don’t know if that’s possible. Anybody ever tried that?
Sorry, was to fast, just moved the bobcat the first time and the fuel gauge jumped to full. Looks like the floater on the sender was stuck. Thanks.
pj, actually joined the forum becuase of your thread. Really good information. Only about one third of my display lights up and it doesn't show the error codes but sounds alarms quite often so I want to switch to gauges. I have a couple of questions for you: 1. What gauges did you use? Just want to make sure that I get ones with the correct ohms. 2. Did you ever get an answer about replacing the fuel sending unit? Mine is broken but I would REALLY like to avoid removing the pumps. Thanks for any help.
Hey Phil, welcome to the forum. I am happy to try to help. I got the gauges from Amazon, cheaper kinds. Here are the links: https://a.co/d/39XCcu6 https://a.co/d/44OWiI5 https://a.co/d/1KJJFCk https://a.co/d/0Q9ru58 No, I didn’t get an answer for the fuel gauge sender, but I was lucky and I didn’t have to change it. But I had to change also my coolant temperature sender which is also in a very tight spot (on the thermostat housing) to remove but it worked out and this one is working now fine again too. The last link is for a continuous use relay, because the one for the glow plugs which I was using to hold my fuel solenoid in, gets to hot and cannot handle the continuous use, so I will have to switch this one too. Lmk if you need more info. Pj
Wow! Thanks for the quick reply. I appreciate the links, did you replace the temp sending unit because the old one wasn't working or because it didn't work with the new gauge? My solenoids are still working so I will probably keep that part of the system intact. I did find a video of someone replacing his sending unit. He had to bend the rod the float rides on but he got it in without removing the pump. Must be a pretty fine line between bent enough to fit and bent too much for the float to move. I guess I will find out! Thanks, Phil
It wasn't working with the new gauge, so I had to change with the one which came with the gauge.
Can you share the link here? Would be interesting to see how he did it. Thanks.
Here you go:
Great! Now we know it’s doable. Good luck on your machine.
How's the machine working out? I have a 7753 with the BOSS system, still hooked up (somewhat) but non functioning. Beeps constantly and I have no aux controls or display. I am putting together a list of how to replace it, especially regarding the aux hydraulics. Did you do something similar? thanks!
Hey smolar, welcome to the forum. Machine is working fine, very glad I did that modification. The fuel gauge is a little funky and is constantly fluctuating, but I can live with that; and also the engine pressure gauge is off and jumps to 100 psi. Otherwise working great. I didn't do a list, whatever I did I tried to show in my earlier posts; just look in there and if you have questions let me know. Good luck.
Aloha pjcat, I was reading this forum. My issue started with that I couldn’t unlock the lift and tilt controls sometimes. Now I can only start it mechanically but can’t drive it because traction needs to be unlocked, very likely that my computers are toast. I’m trying to figure out if all the electronics can be deleted because it’s a mechanical 2001 bobcat 753. I am also in Hawaii on the big island. If you can assist in any way would greatly appreciate it.
Aloha Veebobcat, welcome to da forum. The bobcat you have is a little newer than ours. Of course you can remove all the electronics and just run it mechanically, but then you will also loose so functions with the bucket control etc. Does yours have the BOSS system? Happy to help whatever I can Aloha Pat
Thank-you! I have foot controls for the bucket, and hand levers for driving. I’m not sure if I have boss system if I don’t have that what system would I have? I’m in keaau. Mahalo Vee
I am no bobcat expert. I only can tell from the model we have. I added a picture from what I believe is the type of machine you have, now if you remove all your electronic controls and go fully mechanical, you will lose all those bucket control options you have in there like the bucket positioning. Now, I don’t know if you really want to go this route but maybe it would be also not too bad to fix what is broken. For this, you might have to contact the bobcat dealer and see if they can help you troubleshoot what is wrong. Or you can also try to start a new thread here on the forum and see if somebody responses to your question.