Oil Pressure Switch Woes!

Fatjap

Member
Hi all,
On our 2003 Monaco Knight Diesel Pusher, we had a faint alarm audible when driving on wet roads when there was plenty of road spray, when the road dried out the alarm faded away.
We were led to believe this was because moisture was getting onto the pressure switch diagnosed by previous owners.
Engine is low mileage 22k and the pressure is good.
However we had the switch changed during a routine service ,Cummins had difficulty finding the right switch.
The engine is an ISC330. The new switch (2 wire) was duly fitted, works ok..but the oil pressure gauge reads back to front?...it starts at the top of its scale on idle then drops when revved? it didn't before.
Has anyone encountered this sort of thing before?
I would appreciate it if anyone can shed any light on this strange occurrence .
Any info would be good as we are about to go away for a few days.

Many Thanks
 

adi4

Subscriber
Hi all,
On our 2003 Monaco Knight Diesel Pusher, we had a faint alarm audible when driving on wet roads when there was plenty of road spray, when the road dried out the alarm faded away.
We were led to believe this was because moisture was getting onto the pressure switch diagnosed by previous owners.
Engine is low mileage 22k and the pressure is good.
However we had the switch changed during a routine service ,Cummins had difficulty finding the right switch.
The engine is an ISC330. The new switch (2 wire) was duly fitted, works ok..but the oil pressure gauge reads back to front?...it starts at the top of its scale on idle then drops when revved? it didn't before.
Has anyone encountered this sort of thing before?
I would appreciate it if anyone can shed any light on this strange occurrence .
Any info would be good as we are about to go away for a few days.

Many Thanks

Hi there

In short its the wrong sender for the gauge, some senders go from low resistance to high resistance as the pressure goes up, and some go from high to low. (and some are J1939 CAN, but I'm not going to into that lol)

What you need to do is find the make of the gauge that is in the dash and get a sender to suite.

The sender most probably did not come with the engine from Cummins when it was supplied, when the coach was built the sender would have been fitted with the gauge.

Hope this helps
Adi
 

Jimbo99

Member
Hi all,
On our 2003 Monaco Knight Diesel Pusher, we had a faint alarm audible when driving on wet roads when there was plenty of road spray, when the road dried out the alarm faded away.
We were led to believe this was because moisture was getting onto the pressure switch diagnosed by previous owners.
Engine is low mileage 22k and the pressure is good.
However we had the switch changed during a routine service ,Cummins had difficulty finding the right switch.
The engine is an ISC330. The new switch (2 wire) was duly fitted, works ok..but the oil pressure gauge reads back to front?...it starts at the top of its scale on idle then drops when revved? it didn't before.
Has anyone encountered this sort of thing before?
I would appreciate it if anyone can shed any light on this strange occurrence .
Any info would be good as we are about to go away for a few days.

Many Thanks
Wired the wrong way round maybe
Did they not test it when fitted the new one?
 

Fatjap

Member
Hi all thanks for the input, I see the way Ady is thinking.
Yes the garage did try reversing the wires, and checked the wiring at the gauge end, and had come to the conclusion that it possibly was the low to high or high to low way it may work? but has not as yet been able to find a more suitable sender unit as yet. (the old unit had no part no on it)
The oil switch they fitted the part no is 3015237, the part no reference I found in some of the previous history is 4326849.
Has anyone got any ideas for part numbers or how to tell which way the resistances work?
Tomorrow i'll check the gauge make and see if this gives us any leads.
Many thanks and i'm sure we'll get to the bottom of this.
 

adi4

Subscriber


Earlier Cummins often used 2 pressure switches, 1 for the engine ECU and one for the dash gauge.

That would be a replacement for the Cummins Ecu pressure switch, you can see the oil pressure reading from that sender but only on the J1939 CAN.

They usually have 3 wires, ground, 5V feed and a reference signal ( which will read between 0.5V to 4.5V depending on the oil pressure) it is not a resistance sender.

On most of the later coaches all of the gauges are J1939 CAN, and all of the relevent data that the engine and gearbox can be sent to all of the gauges on the dashboard via just 4 wires, positive, negative, CAN high and CAN low.

Other info like air pressure and fuel level are converted to CAN via the body control module, and their info is sent onto the J1939 so other calculations can be done like instant / ave fuel consumption and range etc.

Hope that all makes sense

Adi
 
Last edited:

RV Neal

Subscriber
Earlier Cummins often used 2 pressure switches, 1 for the engine ECU and one for the dash gauge.

That would be a replacement for the Cummins Ecu pressure switch, you can see the oil pressure reading from that sender but only on the J1939 CAN.

They usually have 3 wires, ground, 5V feed and a reference signal ( which will read between 0.5V to 4.5V depending on the oil pressure) it is not a resistance sender.

On most of the later coaches all of the gauges are J1939 CAN, and all of the relevent data that the engine and gearbox can be sent to all of the gauges on the dashboard via just 4 wires, positive, negative, CAN high and CAN low.

Other info like air pressure and fuel level are converted to CAN via the body control module, and their info is sent onto the J1939 so other calculations can be done like instant / ave fuel consumption and range etc.

Hope that all makes sense

Adi
This is why Adi is considered the God of RV maintenance. A very quick introduction to Canbus systems and multiplex digital wiring technology! My head's still spinning.
 

Popty

Subscriber
If you can get the engine number, then any DAF dealer can check for the correct oil pressure switch, if the switch is correct then a mechanical pressure gauge needs to be connected to check the oil pressure, if the oil pressure is high to start and drops when revved up, then the oil pressure relief valve could be the cause, but a mechanical pressure gauge would confirm that
 
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