Air cleaner light is flikering, both when the key is on and when it's running? New air filters. Unplugged both wires at the sensor/switch - light still flickers. Might be the ignition switch because there where some burnt terminals when we replaced the cab relay but everything was working fine so we left the ign. switch alone. Anything to check for before I take it apart? ----------------------- I don't understand why they have two wires going to the sensor? Isn't it just a ground? Other sensors I've seen have one wire and use the sensor body for ground? There is a diode in the circuit somewhere. I might be able to post shematic if needed Thanks, Rob
perhaps, sounds like something got moisture in it and dried out and got resistive. I would disconnect the negative battery terminal and check plus clean all the connections. If you have a service manual with a schematic in it that would narrow it down to which harnesse(s) would be effected. Also a lot of times, these and other issues are attributed to loose or floating grounds.
The air filter restrictor has two wires because most times there is no good ground on the air filter body, especially anything after the 580SL it's all plastic. The positive for this circuit goes to the light on the dash then to the sensor then to ground. The switch/sensor is normally open. If there is restriction the switch closes and grounds thus turning the light on. So I suspect the wire is rubbed through to ground somewhere between the dash and the sensor. The W wire on the alternator was bad for rubbing through. Just find the wire at the main plug at the dash, cut it a few inches back from the connector and run a new wire.
So, can someone help me read these schematics? :spongebob I normally hunt down problems by looking for charred or broken wires and unplugging things. A few things I really don't understand but would like to: Is the intrument cluster (circuit board) ground or hot? The aircleaner circuit looks like it's making one connection at the board- to the lamp. The terminal on the key switch for the labled GRD. Is this "ground". (Suppose it would be easy enough to test-duh). The sensor looks like it just sends ground up the line to the insrument panel but what's line coming from the keyswitch doing. There is a branch going to the keyswitch line from the sensor with a diode in it. What's that for?
I ain't no Case tech...but I'm going to take a wild guess at the diodes just to make alrman & gggraham's head hurt. LoL :waving The instument panel sends power through the lamps, then wires lead to switches/sensors looking for ground to illuminate lamps. In the case of air filter, hyd filter, and trans filter lamps, these switches are always open (no ground) until the filters are clogged, they never light up otherwise. So, how do you know the lamps are working? You could have a bad lamp, then a filter get clogged, and wouldn't know it. Simple, provide a test circuit for the lamps. Tap into each of the 3 sensors and send them to a ground terminal on the keyswitch. Have the keyswitch made so when you turn the switch to "start position", it also connects a ground to the gnd terminal that the sensor wire goes to. Now while your cranking the engine, it illuminates the three lamps as a lamp test. The diodes prevent feedback between the three sensors. Make Sense? I know I'm stepping out on a limb, but it's worth it for the entertainment. :tong As for your lamp flickering, I'm with gggraham, I think you have a place in the harness rubbed through to a ground. :yup
Yeah, I spent some time Friday and found four different spots that were rubbed through but they weren't the problem. Probably take the floor pan off tomorrow and keep looking. I'd still like to hear gggraham's explanation of how it's supposed to work- according to the diagram. Not that you didn't do a fine job ATCO
ahhh, grasshopper doubts my logic...wants the opinion of professional. I knew this would be entertaining.
Ah but master, wasn't it you who said, "To know the road ahead, ask those coming back"...
Man that's funny! :lmao I knew this was going to be entertaining!
ATCOEQUIP is correct, the keyswitch provides the test ground for those lamps. and since it's only one line for hydraulic filter switch and air filter switch, it needs diodes to avoid interference between the two, in order not to illuminate hyd filter lamp by air filter switch or vice versa. I try to give some simplification of your circuit at http://www.bengkelinovatif.com/explanation.jpg
sensor itself could cause the intermittent problem, try to check the terminal using ohmmeter while you shake the sensor, any connection due to vibration?
Welcome to HEF taufan. Wow! Thanks for those drawings. I think I'm starting to get it. I didn't understand the test part of the circuit. So it means the light comes on when you turn the keyswitch on to show that the lamp is working? Edit: Hey ATCO you had it right but I gotta have pictures.
I unplugged the sensor and started the machine and the light was still flickering.
thanks RobVG! Correct!, the test part is for it. otherwise we don't know, whether the air filter is OK or the lamp is faulty, there must be a circuit to test the lamp, so, when the lamp is off, we are sure that the air filter is OK
after unplugging the sensor cable, try to short pin B (yellow blue) to 'real' ground and see if the lamp lights up steadily. if so, the ground cable from the sensor is faulty, but if not, there is probably some intermittent shortage inside the dashboard circuitry. real ground means any part of the machine which made of metal and not coated by anything
I could get to like you ATCO. :notworthy That "test" circuit is called a 'telltale' here in Australia. ..........another bit of useless information PS sorry I haven't helped on this one ROB, but for what it's worth check - 1) the plug going into the dash, the little tabs from the printed circuit sometimes bend & don't make contact with the connectors on the plug 2) air filter bulb connections 3) the dreaded main plug under the floor - above RH axle :drinkup
Ahh grasshopper, yet, it is eyes which blind the man. You must see with your mind. :cool2 LoL, I've been telling myself that very thing for years! :yup
how is the troubleshooting going? any luck?
Is that something like "Use the force Luke..." ?:falldownlaugh Well, Got R Done. Took up the floor pans, started it up and started pulling and tugging from the sensor on back. I got the light to go out way in the back. The harness had rubbed through where it was wire tied to a steel tube just before it went up into console. Thanks for all the help you guys- you're awesome...
:woohoo :drinkup
Damn wires that rub through! But on those machine I've seen it 100 times. The one problem we had on a few units was when you pulled the park brake on the unit wouldn't start unless you press the declutch button on the loader lever. If you took the park brake off it would start no problems. Always that harness with the plugs below the floor. Tied to the tube and sometimes tied to the park brake cable.