I routinely check all my fluid levels before startup but my oil and hydraulic level lights come on during the prestart monitoring. I always check the engine oil on level ground before any cranking (to ensure all oil is in the pan) and the oil level is right above the "FULL ENGINE STOPPED" mark but I generally get the engine oil level light to come on during the prestart monitoring. Same is true for hydraulic oil: looks good in sight gauge but get the level indicator light. I don't know if I have a bad sensor, circuit, wrong dipstick, or something else but it really bothers me to see an engine oil level warning light when I run the machine. Thoughts?
There is a "self test" function for the lights when you first turn the key on. Is it this that you are seeing, or do the lights not disappear until after starting the machine.?
When I first turn the key on (not start), I get all the light and then hear the audio beep for a sec without any lights. After the audio silences and all the lights extinguish, these two lights then come on after what I assume is the premonitor check referenced in the O&M manual which should indicate low fluids...even though I manually verified fluids are good. The lights stay on even after starting and do not extinguish.
That sounds wiring-related to me. If it was sensor-related then they might probably go out at different times - unless both sensors happen to be bad that is. So you could have 2 bad sensors or some bad wiring. A bit of a scattergun approach but try replacing the cheapest of the two sensors and see what happens. If the light for that function goes out then replace the other sensor. You do have an electrical schematic, correct..?
I think its wiring problem check your sensor connectors if they are not : Dirty Wet Lose Check your sensor wires for broken and short And try to change your sensors Some times if the machine is not cleaned regularly it affects the wire insulation (it will break) due to moisture therefore you start to experience serious shorts on your electrical circuits.
Okay- I'll verify the sensor wiring is good before anything else. Any idea what the voltage or signal is to the sensors? Would like to also verify the sensor is being pinged correctly.
[QUOTE="You do have an electrical schematic, correct..?[/QUOTE] Yes. Just happened to get a schematic from someone on the board a few months ago.
Thought so........ Check out the continuity of the wiring harness for the two sensors right up to the monitor panel (or wherever they finally end up) might be something to check before splashing out on new sensors. But at the end of the day it may be nothing more complicated than you have two sensors both bad at the same time.
Sheesh. Just unplug the hydraulic level sensor and retry. I've changed quite a few level sensors on the hydraulic tanks on my 322Bs and 330Bs that I used to have. Only ever changed one engine oil level sensor. I seem to recall that when either one was bad, both lamps stayed lit, but, it's been a long time.
That's sounds like a good plan. I like the easy, common sense method first. By the way, the schematic shows the oil and hydraulic level sensors are two-wire, normally open switches with one wire being a ground. Assuming these are strictly mechanical sensors, I'm sure I can jump the two pins, completing the circuit, and mimic a closed or 'full of fluid' reading. My guess is the pink wire is a steady voltage (+5V, +24V, etc.), it's probably just a mechanical open switch and the computer is reading a short to ground (0 volts) as full of fluid when closed. A stuck 'open' will not go to ground. If there is an AC type signal like a transducer-based sensor, then all bets are off. I'll break out the trusty Fluke and get back to everyone. May be a day to two...
The hydraulic is just a plasti-float with a metal insert. When it don't float, it drops down onto two pins. No high tech. Can't recall the engine sensor style.
I was able to climb on the machine for a few mins today while out doing errands. I found there is an issue with the hydraulic level sensor. When I was reached in to unplug the sensor, one of the wires broke free- I'm sure it was broke internally and didn't make a complete circuit. To quickly verify, I shorted the plug with a special tool designed to short plugs (you may know it as a paperclip) and my hydraulic low level warning light finally extinguished on the monitor. My guess then is this circuit is normally open without fluid and then closed when enough fluid is present (ie- the metal float goes up and contacts the two pins completing the circuit). This makes sense from a fail safe perspective like when my wire broke. The warning light will only go off when there is a complete circuit and full of hydraulic fluid but show a low level fault with either a broken wire or actually low. I didn't have time to crawl too deep in the engine bay to play with the engine oil level sensor- hope it will prove an easy diagnosis too. So...the big question now: When I replace the hydraulic fluid level sensor, will this be a very messy swap by removing the old one and then as fast as possible screwing in the new one? Any tips other than draining the hydraulic tank below the sensor level?
It is capable of lifting itself to extremes or being parked on a steep slope to lessen the head of oil behind it. And, definitely relieve the hydraulic tank pressure.
Lower the fluid level in the tank as much as possible by raising the boom in the air to the maximum, curl the bucket and retract the stick until the curled bucket is almost touching the boom. Then park the machine on a slope as recommended above, and be quick doing the replacement. Either way you're probably going to get your hands a tad wet........ As you said, the other alternative is to drain out sufficient oil so that the level is below the switch. If you do it that way make sure that the containers you use to drain the oil into are spotless - at least if you're planning on putting the drained oil back in the tank again.
Thanks- that's great info about extending all the cylinders and parking downhill. It's obvious to do those items...but only after I heard it from someone else Relieving the pressure is not something I would have thought of so very glad to know it. Would have made for a nasty surprise otherwise.... This also reminded me of a method I heard on my pickup truck forum on how to replace leaky oil drain plugs without loosing oil. Guys will stick a shop vac into the oil fill port and pull a vacuum on the crankcase. Then crawl underneath the truck and swap the crush washers or switch plugs while air is being sucked into the drain not allowing the oil to escape. I won't have that luxury where my machine is located but I'll manage.