Cat 426 Oil light + Horn + Neutralised Transmission

   / Cat 426 Oil light + Horn + Neutralised Transmission #1  

fitterski

Gold Member
Joined
Oct 20, 2016
Messages
377
Location
Nouvelle, QC
Tractor
1987 Cat-426, 1991 Deutz-Dx-6.05, 2019 Husqvarna 2xHP
I'm looking for answers about on 2 other forums, no solutions thus far :-(

Ser# 7BC01181 (1st made-in-england series with Perkins engine)

This morning after about half an hour light snow-work

- the warning horn sounded
- the oil light came on
- the machine stopped moving.

Now if I start cold I have about 10-20 seconds during which I can move 100 feet and that's it.

I haven't got the faintest clue since ENG oil 'pressure' is 70psi, the ENG oil-pressure-switch or pigtail I cannot find at all, and in any event ENG oil-pressure or the ENG oil-pressure-light or the horn have nothing to do with the transmission neutralizing. Maybe I have a double malfunction, a lose wire grounding???

The neutralizing solenoid energizes on button-push so a lose connection would cause failure to neutralize.

Any ideas?
 
   / Cat 426 Oil light + Horn + Neutralised Transmission #2  
I’m not familiar with this exact system but it sounds to me like it “detects” low oil level and/or pressure and instead of the typical engine reduction it puts the transmission in neutral and sounds the horn as an alarm. Check your oil level, obviously, and then find that oil pressure or level sensor and either bypass it (as a test) or do a resistance test on it and see if it’s working. Once you’re positive you’ve got a good sensor you can move on to electrical issues. But it sounds like a sensor to me
 
   / Cat 426 Oil light + Horn + Neutralised Transmission
  • Thread Starter
#3  
Thanks,
The oil pressure transmitter/gauge is aftermarket and was validated when installed with a mechanical gauge. I know of no oil-level sensing as such on the engine. I presume it's the original oil-pressure switch that trips the oil-pressure red light and the horn. I had this before momentarily with extreme nose-up attitudes a couple of times but NEVER with a concurrent transmission cutout. The problem is I cannot find the Pr-Sw or its pigtail, some books show it on the oil-filter adapter but mine has nothing there.
 
   / Cat 426 Oil light + Horn + Neutralised Transmission #4  
Typically your oil pressure switch will be in the side of the block about 3/4 of the way down towards the oil pan or on the oil filter housing in some applications. Stupid question but have you physically checked your oil level on the dipstick? Also, you said you were doing snow work so there’s a very good possibility that the oil is too thick for your weather conditions. I’ve personally never run into that issue but I live in the south and don’t know what snow is. Haha. But I would assume that’s a possibility. Your gauge may be showing good pressure as the pump tries to push it through but you’re not actually moving it anywhere. Like squeezing a syrup bottle as hard as you can and almost none coming out. Just spit balling there but, assuming you do have, proper oil level, I would definitely find that sensor and test it. It’s there somewhere. Every engine has one. But your symptoms definitely lead me to believe you machine thinks it’s out of oil and therefore is refusing to work. USUALLY the engine won’t start on low oil pressure but this may be different programming. Especially since it sounds like it’s switching to neutral instead of power reduction.
 
   / Cat 426 Oil light + Horn + Neutralised Transmission
  • Thread Starter
#5  
The 15w40 oil is quite liquid on the stick @ -2c, about 1/2" above max.

I suspected maybe a neutralizing solenoid so I disconnected it, no change. Don't think it's related but now the the oil pressure light remains off and doesn't even test. I only get the horn and no fwd/rev. No luck with the oil-pr switch OR the pigtail, just no sign of either so I wonder if it wasn't simply removed when the pressure gauge was installed, but then what is triggering the horn, now without the light? A shorting pigtail plug left loose somewhere?
 
   / Cat 426 Oil light + Horn + Neutralised Transmission
  • Thread Starter
#6  
..Don't think it's related but now the the oil pressure light remains off and doesn't even test. ...

I pulled the light module and worked the light socket wires a bit, the oil-pr light does work and test. First attempt this morning I got the horn after maybe 1 minute, on the last attempt i did some light work for about 10 so it seems like it's not a very fixed delay.
 
   / Cat 426 Oil light + Horn + Neutralised Transmission
  • Thread Starter
#7  
Tried to trace wires from the test switch: one black is grounded right there, of 2 #405 greys one goes to the light the other looks like to the gauge cluster in the back of the bus. No other wires, don't see any going to engine bay so far.

Meanwhile I noticed on test starts that the condition develops gradually, rocking fwd/aft in 1st gear for example the response speed decreases until there is no response. With the floor panel pulled when giving gas to move I hear what resembles the sound of chain on a chainsaw but it's rather faint. I don't like the smell of this, could be the tranny.
 
   / Cat 426 Oil light + Horn + Neutralised Transmission #8  
Pull the sensor and see if you have an open circuit with an ohm meter.
 
   / Cat 426 Oil light + Horn + Neutralised Transmission
  • Thread Starter
#9  
Pull the sensor and see if you have an open circuit with an ohm meter.

if you mean the oil-pr-switch I can't find it, nor the wire going to it
 
   / Cat 426 Oil light + Horn + Neutralised Transmission
  • Thread Starter
#10  
Meanwhile I noticed on test starts that the condition develops gradually, rocking fwd/aft in 1st gear for example the response speed decreases until there is no response.

To clarify, the move fwd or aft response degrades with each slow rock over a couple of minutes. The horn comes on at the end when there is next to no more response.

Very many wire #'s and colors are not at all what's in the book.
 

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