Have a cat 311 that I think the engine pickup sensor is bad. The sensor is reading 2.2k ohms when disconnected. Does that sound right ohm wise? Next question is what voltage should be going to the sensor? Out of the computer I'm not seeing hardly any voltage going to the sensor. Thanks
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Cat excavator wiring?
- Thread starter drew good
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Nige
Senior Member
With a machine Serial Number I could look up the spec of the sensor, if one exists.
Nige
Senior Member
Sorry, I can't find a resistance spec for it anywhere.
TBH generally 2-wire speed sensors like that one are magnetic and work on the Hall Effect principle. They wouldn't have much if anything in the way of power coming from the electronic control.
TBH generally 2-wire speed sensors like that one are magnetic and work on the Hall Effect principle. They wouldn't have much if anything in the way of power coming from the electronic control.
Nige
Senior Member
Have you removed it.? What was the condition of the tip like.? Any metal chips stuck to it or was it chewed up.?
Remove, clean, & reinstall might be a good 1st step.
Remove, clean, & reinstall might be a good 1st step.
John C.
Senior Member
In my experience all the manufacturers speed sensors fail in two modes. They either short through with no ohms resistance between the wire connectors and the side of the metal sensor or they have infinite resistance. The metal that Nige brought up does interfere with the signal and will make for plenty of head scratching. It generally means the drive damper, and auxiliary drive gear for a pilot or auxiliary pump or the input bearing to the pump is in process of going bad. Do you have oil in the damper case?
So what exactly is happening/not happening?
The engine won't go above idle or the sensor won't read above idle through the monitor?
As with Nige, I can't find a spec for that particular sensor, but from experience I would say maybe about one or two hundred ohms. A multimeter with frequency measurement can give you a rough pass or fail test.
It sounds like you have a problem with the auto/manual switch and/or wiring. When the switch is in manual, are you able to change engine speed via the dial or the backup switch? Your post isn't clear.
For now based on the info given, forget about the speed sensor.
The serial number you quoted isn't good, but probably good enough. Attached schematic which will be correct provided that the last digits of your serial number aren't higher than 00261.
For now based on the info given, forget about the speed sensor.
The serial number you quoted isn't good, but probably good enough. Attached schematic which will be correct provided that the last digits of your serial number aren't higher than 00261.
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Nige
Senior Member
I read the S/N as 9LJ00201.......... completely missed the other "2" at the beginning.
Chrisso
Senior Member
So, under normal conditions with auto/man switch in AUTO, and with AEC activated, your issue is the engine won't go above idle right?
Then when you switch it to MAN, and the A appears on the screen, you can bump the idle up/down using the back up toggle switch next to it right?
If that's the case, yes a bad engine speed sensor could cause this, but so could any other fault with the electronic control really.
On backupSw1 and backupsw2 on the drawling should one of those have power coming out of the controller or are they both just inputs?
Yes they both look like inputs, they would tell the electronic control to forget about the engine speed dial and AEC altogether. I'd have a good look over the machine visually first and look for any rubbed, melted wiring, etc
Just my thoughts.
P.S. Type your replies under the quote when quoting someone.
Then when you switch it to MAN, and the A appears on the screen, you can bump the idle up/down using the back up toggle switch next to it right?
If that's the case, yes a bad engine speed sensor could cause this, but so could any other fault with the electronic control really.
On backupSw1 and backupsw2 on the drawling should one of those have power coming out of the controller or are they both just inputs?
Yes they both look like inputs, they would tell the electronic control to forget about the engine speed dial and AEC altogether. I'd have a good look over the machine visually first and look for any rubbed, melted wiring, etc
Just my thoughts.
P.S. Type your replies under the quote when quoting someone.
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hi,
as you said
'I have jump the wires from the controller straight to the switches in the cab to bypass all the wiring and still doesn't work'.
i think you should not connect the two wires from controller to the switches you mentioned. i assume that you mentioned here as switches for governor back up switch and speed change switch (toggle switches). if you do so there might be a chance of damaging the controller.
because these 2 wires from controller brings the signal to operate the governor motor according to the input signals to controller from the speed change dial knob. so these 2 wires are out put from the controller.(B740-OR & B739-WH).
so when the governor backup switch is at the auto position it connects these 2 wires to A763-GYwire & B751-YL wire which goes to the governor motor. when this circuit is completed then controller is operating the governor motor according to the input from the speed dial switch.
when the governor backup switch turns to the manual position it by passes the controller (B740-OR & B739-WH wires) and connects the governor motor wires (A763-GY & B751-YL) to speed change toggle switch. this speed change switch has provided key switch voltage so when you move the toggle switch up and down it passes the current to both directions through the governor motor. therefore now you can increase or decrease rpm.
as you asked
'On backupSw1 and backupsw2 on the drawling should one of those have power coming out of the controller or are they both just inputs?'
they are inputs to the controller. at manual mode when you move the speed change switch up & down at that time only it sends the signal to the controller.
i think in this case as you said that always 'A' displays on the monitor though you move the governor backup switch to auto & manual positions that means
1.Governor backup switch has stuck in side the manual position or
2. B740-OR & B739-WH these 2 wires from controller is faulty.
you can bypass this switch by connecting (B740-OR & B739-WH) wires to the (A763-GY & B751-YL) wires at the governor backup switch. (refer the Schematic well)
if this doesn't solve the problem then you have to inspect the 2 wires from controller (B740-OR & B739-WH ) for there conditions. if both the backup switch & 2 wires are good then there may be a problem inside the controller.
i think these are the 3 possible things could happen in this case according to my knowledge.
Hope that this will help.
good luck.
Yes the machi5eill
Yes the A is always on the screen no matter which position the switch is in . We have never seen the A on the screen before until this problem started . Not sure but i dont think it will let me select AEC since i have the A on the screen. Yes the machine will not go above high idle unless you put it in man and use the toggle to increse the speed. Thanks
Does the speed change toggle switch work to change the rpm even in governor backup switch at Auto position. did you check that?
Yes I did check that it only rev up if it's in man.
Did you by pass the back up switch and try as i said from the earlier post ?