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Cat 963C oil pressure light never comes on?

AMBMike

Active Member
Joined
Jun 12, 2009
Messages
41
Location
Central PA
Hi guys. Long time lurker first time posting. Lots of valuable info and expertise here but this time I haven't found an answer to my specific problem.
We have a Cat 963C track loader (serial # BBD00739) that has never shown the engine oil pressure light other then at startup. Shouldn't it come on for the first little bit after changing oil?
We've got some time now and it's in the shop so we'd like to chase it down if it is in fact a problem.
Any advice, wiring diagrams, testing procedures, sensor locations, etc are greatly appreciated!
Thank you!
 

walkerv

Senior Member
Joined
Jan 21, 2016
Messages
1,125
Location
wingate nc
Put a mechanical pressure guage in ,change oil see if it builds oil pressure fast like the dummy light is telling you ?
 

AMBMike

Active Member
Joined
Jun 12, 2009
Messages
41
Location
Central PA
And another issue on the same machine.
The engine warning light (looks like a end view of an engine block with an explanation point inside) comes on occasionally. This is not the main warning light, just the little one. Also no warning buzzer when it's on. No active or stored codes.
Thank you!
 

AMBMike

Active Member
Joined
Jun 12, 2009
Messages
41
Location
Central PA
Put a mechanical pressure guage in ,change oil see if it builds oil pressure fast like the dummy light is telling you ?
Thanks walkerv. I should have mentioned first that this machine has had previous issues with the wiring harness. We think it may be harness related again??? We'll definitely keep your suggestion in mind
 

walkerv

Senior Member
Joined
Jan 21, 2016
Messages
1,125
Location
wingate nc
Thanks walkerv. I should have mentioned first that this machine has had previous issues with the wiring harness. We think it may be harness related again??? We'll definitely keep your suggestion in mind
Unfortuently im on my lunch but im sure others will chime in shortly. Was just following the KISS theory to make that suggestion so you know you actually have good oil pressure .
 

Nige

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Jun 22, 2011
Messages
28,984
Location
G..G..G..Granville.........!! Fetch your cloth.
If you have had wiring issues then your check engine light could well be a false alarm. No harm in checking though.

Click on my username and start a conversation with me that includes your email address. I'll send you some schematics by mail.
Do you have an Operation & Maintenance Manual..? Did you know you can download one from Cat for $46.......

upload_2019-3-6_17-0-43.png
 
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AMBMike

Active Member
Joined
Jun 12, 2009
Messages
41
Location
Central PA
I like the KISS theory... I'll mention it to the shop guy. I'm just an operator with a background in commercial and residential wiring who works in the shop when we can't work in the field. ..
 

AMBMike

Active Member
Joined
Jun 12, 2009
Messages
41
Location
Central PA
Thanks for the input guys and especially thank you Nige for the schematics. They were a big help .
So I located and tested the harness for the engine oil pressure sensor and it's all good. Asked our shop guy if I should get in deeper. He called Cat and they said it's normal to never see the low oil pressure light unless there's an actual low oil pressure situation. So our worries were apparently for naught. (Or not???) He also decided to let the other light go for now as it comes and goes randomly and never sets off the main alarm light or buzzer.
I guess we'll see how this goes...
 

kshansen

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Mar 11, 2012
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11,129
Location
Central New York, USA
Occupation
Retired Mechanic in Stone Quarry
I know on some of the Cat machines there is a way to have the "monitor" show real time readings like pressures or temperatures. I tried finding that info on the machine in question and did not see it right off.

One thing I did note that might be of interest is the engine oil pressure sensor and the fuel pressure sensor are both 194-6725. Note that these are not just simple on off switches but actual pressure sensors that "report" to the ECM and then I assume the ECM decides how to interpret the reading and turn on or off the light in regards to programmed settings.

I could see the designers selecting to have the ECM disregard a low pressure reading on start up for say five seconds to avoid panic by operator!
 

AMBMike

Active Member
Joined
Jun 12, 2009
Messages
41
Location
Central PA
Our D series track loaders and K2 series dozer can monitor temps and pressures in real time but I haven't found a way to do that with the C series loaders.
Can someone explain in simple terms how these sensors work and communicate? I see in the schematics they have a battery+, negative and signal wire. Out of curiosity I put my test leads between battery+ and negative and got a reading of 5 volts with the key on and engine off. Do they output a variable voltage on the signal wire?
 

Nige

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Jun 22, 2011
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Location
G..G..G..Granville.........!! Fetch your cloth.
It’s a stabilized DC voltage supplied from the ECM, not battery+. If you follow the wiring back from any sensor you’ll find all three wires go back to the ECM. Sensors can be 5V, 8V, or 10V depending on type, so some ECMs will produce all three voltages. In this case the voltage is 8V, pin #12 on the RH of the ECM is the +8V, pin #15 on the LH side is the return (ground).
upload_2019-3-7_3-6-34.png
A lot of sensors produce a PWM signal which is basically a square wave where the width of the pulse is equal to the % reading of the sensor. See the link below which attempts to explain it.

https://www.heavyequipmentforums.co...amation-warning-and-beeper.57116/#post-616452
 
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walkerv

Senior Member
Joined
Jan 21, 2016
Messages
1,125
Location
wingate nc
Our D series track loaders and K2 series dozer can monitor temps and pressures in real time but I haven't found a way to do that with the C series loaders.
Can someone explain in simple terms how these sensors work and communicate? I see in the schematics they have a battery+, negative and signal wire. Out of curiosity I put my test leads between battery+ and negative and got a reading of 5 volts with the key on and engine off. Do they output a variable voltage on the signal wire?
To put it simple as possible the 5 volt vref as most of us know it is the power supply to the sensor .the sensor varies that 5 volt onto the signal wire where the ecm and program them come up with the pressure or other parameter based on the voltage on the signal wire . Not sure exactly how the sensor does it exactly i will leave that part to smarter people . Our cars have been covered in those style sensors for ages diesels once they became electronic
 

AMBMike

Active Member
Joined
Jun 12, 2009
Messages
41
Location
Central PA
Thanks guys that gives me an idea of how it works...
I like running the new machines with all the creature comforts and tight and quiet cabs but prefer working on the older simpler machines...
 
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