950g cat loader warning light stays on

Nige · Feb 26, 2019

Have you replaced the breaker relief valve on the tank yet..?

Lewis12 · Feb 27, 2019

Yes but no change the breather I got was 507-0646 cat# it didn’t have the push down to relief the air. But it had the same nipple to screw down on the tank. Parts book show a screen on the inside of the tank where the return line from the filter goes through the tank. Not sure if that screen could be plugged? Haven’t put a gauge on the sending unit either.

kshansen · Feb 28, 2019

Lewis12 said:
Yes but no change the breather I got was 507-0646 cat# it didn’t have the push down to relief the air. But it had the same nipple to screw down on the tank. Parts book show a screen on the inside of the tank where the return line from the filter goes through the tank. Not sure if that screen could be plugged? Haven’t put a gauge on the sending unit either.

SIS does show the original breaker/breather 133-1963 changing over to the 507-0646.

Not saying the return line screen can not be the problem but the screen in the return lines for most systems have fairly large holes in them. Now I could see if someone had worked on the machine and stuffed a rag in a fitting or line to keep dirt out and forgot to remove it before hooking up hose there could be enough in the screen to cause back-pressure. Getting to the return line screens means splitting the tank so I would eliminate everything else first!

I still would recommend trying to test with an actual pressure gauge teed into the port the send er is mounted in just to know 100% sure you are seeing too much pressure there. Then I would be trying to move the pressure gauge from the inlet side of the filter to the outlet side of the filter. This will tell you if the pressure is high because of the filter or some problem in the tank.

One more idea/question what filter are you using on this machine? I see you mention it was the "correct" one from Cat but what is the actual part number on it? The more information the better chance of an answer.

Lewis12 · Feb 28, 2019

1g8878 cat filter the tranny filter is the same also. Also when that pressure switch alerts the operator that the filter is plugged. Does the oil bypass in that filter head to make up for the plugged filter?

Lewis12 · Feb 28, 2019

One more thing the filter am seeing in parts book dosent show the big holes for the screen on the hydro filter return side. But the other screen inside the tank that goes to the pump I believe does show the big screen holes. That's why I was thinking the filter screen could be kinda plugged.

Lewis12 · Mar 7, 2019

Removed the pressure sending unit on the hydraulic oil filter base and I am getting 20-21 psi at idle. And at high idle roughly around 24psi. I tried putting the gauge on the quick connect fitting near the pressure sending unit first to leave the sending unit connected but the pressures were not the same at that quick connect. Now am thinking the problem might be in the screen inside the tank?

Nige · Mar 8, 2019

An idea from left field. Could there be a loose piece of the inner liner of the hose between the filter and the tank that is restricting the flow and causing back pressure..?
Another thing you could try is unscrewing or removing the tank cap as a test.
That would be the last throw of the dice before pulling the tank apart, which iirc requires the tank to be removed from the machine. I haven’t looked at it for your machine but usually the return line has a baffle (cylinder full of big holes) in the tank rather than a screen to disrupt the flow as the oil returns to the tank. I’d be surprised if that was causing a restriction unless something has collapsed.

Nige · Mar 8, 2019

I have to apologize. It is a screen in the tank. Attached the parts breakdown for information.
I think I would still look at the return hose from the filter housing to the tank to make sure it's not partially blocked inside before ripping the tank off the machine.

kshansen · Mar 8, 2019

Even if the return flow has to go through a screen and not just a pipe with large holes in it something has to be plugging that screen! But I agree I would start it up with the gauge connected then loosen the cap to see if there is a drop in pressure. Just be ready if there is a rush of oil out of the tank!

If that does not drop the pressure then check the return hose like Nige says, it might as well be the first thing off when getting ready to drop the tank.

And please be sure to take lots of pictures of what you find. Both for your self and those of us here who are dying to know what the problem ends up being!

John C. · Mar 8, 2019

If that sender is reporting differential pressure across a filter, what difference does a restriction in the tank make? The pressure will just backup and the filter will show the same pressure on both the inlet and outlet ends of the filter housing.
Find a way to put a gauge in both sides of the filter to see what you actually have and troubleshoot from there.

kshansen · Mar 9, 2019

John C. said:
If that sender is reporting differential pressure across a filter, what difference does a restriction in the tank make? The pressure will just backup and the filter will show the same pressure on both the inlet and outlet ends of the filter housing.
Find a way to put a gauge in both sides of the filter to see what you actually have and troubleshoot from there.

Wish I could see that pressure switch/Sender. Not sure if it is a differential pressure switch like say the 988H transmission filter we had at work or if it is just a straight pressure switch. Kind of sounds like a straight pressure switch because of the way the schematic refers to the open/close pressure and does not have the word "differential" in the specification. But then we all know what happens to those who "assume" anything.

Lewis12, if you are reading this can you maybe post a picture or two of the switch to help us understand what it is for sure??

Nige · Mar 9, 2019

It's a straight pressure switch Ken, #2 in the illustration. It's plumbed into the filter inlet port and when the pressure in the incoming line rises high enough (as it would if the filter was plugged) it sets off the filter change warning.

kshansen · Mar 9, 2019

Nige said:
It's a straight pressure switch Ken, #2 in the illustration. It's plumbed into the filter inlet port and when the pressure in the incoming line rises high enough (as it would if the filter was plugged) it sets off the filter change warning.

That's what I was thinking but I was just responding in reference to John C's post. Trying to be positive about the way the thing works and not send someone down a rabbit hole trying to fix something that is not broke.

After my experience with a certain 988H to say I don't trust Cat schematics or description of operation writings would be an understatement! At least my cheapness and stubbornness saved me from replacing an expensive ECM that was working perfectly despite what the tech expert at the dealer had said the problem was!

John C. · Mar 9, 2019

The switch could be a pressure switch but the manifold could be ported in such a way as to only show a differential. Filter restrictions I've worked on in the past were always set up to show differential across the inlet and outlet. What does the schematic show?

Nige · Mar 10, 2019

Not much John. It doesn't even show the pressure switch although other pressure switches (e.g. brake accumulator pressure) are shown. #61 is the hydraulic filter, I assume HH is the test port that the OP mentioned earlier.

rondig · Mar 10, 2019

NIGE your solution is always good....but a properly sized piece of black tape over the light is better for u guys....win win so to say...you get to really fix it...and he doesnt see the.light lol

Nige · Mar 10, 2019

Personally I'm hoping that it is something inside the return line between the filter and the tank, because removing the tank in order to disassemble it in order to get at the return screens is not an easy job.

kshansen · Mar 10, 2019

The HH is the oil sample port. I was looking into the schematics myself but got called away to visit Grandson in Hospital, appendix operation yesterday, only five years old and not a happy camper, but doing OK.

E3 is the location in the schematic drawing in case anyone is wondering!

Lewis12 · Mar 14, 2019

The service Manuel appears to show the pressure setting of the hydraulic oil filter bypass valve to be at 25psi. So does this mean when the pressure at the pressure switch on the filter housing reaches 25psi it sets of the hydraulic filter plugged warning light? Before I think about opening the hydraulic tank I do see the screen in th3 tank does have big holes which would be hard to plug up. So instead I am looking into first flushing out the tank and adding new oil and new filter. I think the oil may have a little containmintion and need to be replaced. Because when I had the wire connected and buzzer disconnected the light wouldn’t always be on but when it would come on it would come and go. But sometimes stay on for like 10 min then go away.

Lewis12 · May 1, 2019

Update i got the light to go away. The hydraulic fan motor stopped working so the machine got hot. Once I replaced the hydraulic fan pump with the new one I also drained the hydraulic tank and added new oil. Now the hydraulic filter indicator on the monitor with the tattle tail lights doesn’t come on and everything is functionaling normally. Not sure if the pump was causing the issue or if the draining and adding of the hydraulic oil fixed the problem but it’s work8ng now. I really think it was probably the oil being contaminated in the tank. But anyways just wanted to make an update.

950g cat loader warning light stays on

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