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nosgsxr · 10-16-2019, 09:09 AM

i have a 5.9 1999 and have an oil pressure gauge that is pegged out on the dash. my scan gauge d unit is still reading the oil pressure and its fine. i would like to get the dash gauge working again. it worked fine till about a month ago. the gauge is pegged out with the key on or off. i found a sender or switch on top of the oil filter housing. it has two terminals on the top with only one wire hooked to it. i can take the wire off and there is no change with the dash gauge. my question is where does the scan gauge get its reading from? and why is there only one wire hooked to the switch/sender on the filter housing? im guessing that this is a low/no oil pressure switch the goes to a light or horn. what the odds of the gauge in the dash going bad? thanks for any help

Jim_HiTek · 10-16-2019, 09:31 AM

The gauge on the engine of my 5.9 Cummins on a Freightliner chassis was a 2 wire unit. One wire goes to the idiot light, and illuminates it when the oil pressure is low, that is the switch type. The other wire is a resistance type that goes to the oil pressure gauge, that is the analog type. Check to see if your idiot light comes on when you turn the key on. It should illuminate, continuously if the gauge is connected. That's the switch type.

You can have another Analog gauge somewhere on the engine. No rule says they have to combine the two functions and someone could have put in the Switch/Analog type to replace a bad single function unit. So look around for another pressure sender on the engine.

My gauge stopped working in my '94 Bounder and I spent a year after that driving around the country and when I'd find a truck parts store I'd ask about the oil pressure sender. Finally, in Fairbanks Alaska of all places, at an old timey trailer parts store, the counter guy said, yeah, I have those, just needed to tell him it was a Cummins on a FL chassis. Cost $25. Unscrewed the old one, from the bottom front, on the passenger side and screwed in the new. Sold that RV in 2016, did the gauge work in 2012 so don't remember all the details.

nosgsxr · 10-16-2019, 11:36 AM

so your dash gauge was not working and when you replace the one on the lower part of the motor it worked again? i will get under there today and see if the one you are talking about has two wires. some how i can still read the pressure on mt digital gauge that is hooked to the port under the dash. i just want all gauges to work. thanks for the info.

Jim_HiTek · 10-16-2019, 03:48 PM

Quote:

Originally Posted by nosgsxr

so your dash gauge was not working and when you replace the one on the lower part of the motor it worked again? i will get under there today and see if the one you are talking about has two wires. some how i can still read the pressure on mt digital gauge that is hooked to the port under the dash. i just want all gauges to work. thanks for the info.

Yes, that's what happened. The dash gauge was pegged and had been for over a year. After I replaced the sender, back to normal. Worked fine for 5 years after that until I sold it.

kidz_driver · 10-16-2019, 06:44 PM

The oil pressure sender on top of the oil filter head is an OEM addition and works by varying resistance to ground.

On the 5.9 ISB there is a Cummins oil pressure sensor which is located on the block, on the passenger side of the engine. This sensor provides data to the ECM which is where your scangauge obtains is information.

The Cummins Quickserve website has great information on location of the engine related sensors.

Dave

nosgsxr · 10-17-2019, 06:13 AM

update......ok i got the sender/switch off the top of the oil filter and looking to replace it. no change on the dash gauge. this one only has one wire and i guess it grounds when screwed into the block. i found the sender on the passenger side of the motor and its a 3 wire. when i unplug it it turns on a check engine light and it appears to run different. plug it back in and i can read the pressure on my scan gauge but still no dash gauge difference.

i have just signed up on the quick serve web site but didnt have my motor # i think i have a block # now and will see what i can find.

kidz_driver · 10-18-2019, 04:44 AM

The oil pressure sender can be tested for continuity using an ohmmeter measuring from the terminal to the base.

Infinite resistance would indicate that the sensor is faulty, the same as disconnecting the wire attached to it.

If the gauge moves to zero when you touch the wire to ground it is likely that the problem is with the sensor.

If the gauge does not move when you touch the wire to ground the problem might be with the gauge itself or the wiring to the gauge.

I recall reading in previous posts where dash gauges on some older motorhomes built on a Freightliner chassis had a problem with cold solder joints on a dash control board.

If the problem is not the pressure sender you may want to Google that for more information.