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My oil pressure gauge was working fine until I started it up leaving for work today. It just went straight to the 110 point after starting which never happened before and it stayed that way even past operating temp. I got home, read a few posts from the forums and I was able to locate where the sensor is connecting to. I wanted to start a new thread due to the old threads being cut off and almost 15 years old
Anyways, after a few forum reads, I tried disconnecting the wire to see the gauge reading and sure enought it jumped straight back to past the gauge max. So from what ive read, it's a wire/gauge issue. I wanted to simplify it and keep the reliable reading by opting into a mechanical gauge. I was able to have my fiance's permission to grab the mechanical oil pressure gauge from his FC but now I couldn't figure out how to put that onto the stock one I have on since a connector slides in there.. I did try cleaning the connector and the unit a little bit and started the car again and that seemed to fix it, until I started the car again and it's back to reading max. So im making a quick stop to the store to get some alcohol to actually clean the contacts in the meantime.
My question is.. how exactly do I stick that end of the gauge onto my sending unit?
Image 1: The reading it gives me few seconds after starting
Image 2: The oil sending unit
Image 3: The mechanical gauge I pulled from the FC
To use the mechanical gauge, you need to remove the factory sending unit and add a brass fitting that will fit the factory iron hole size on one end and whatever connection you have for that mechanical gauge. Probably easier to just grab the connector from the second gen you got that mechanical gauge from.
Try grounding the wire that is attached to your current sending unit and see what the gauge does.
For a quick reading I like machinal gauges but for running into the cabin, I don't like them.
@KansasCityREPU man, youre the goat - i appreciate you always responding on here. I went and looked at the second gen and it looks like a fitting was in place of the oil pressure gauge unit so I'll be going that route when i have to, but for now looks like some issue with the wiring/contact since it did have a pressure reading from some slight cleaning.
How exactly do i ground the wire? My apologies - i am not well versed in electronics just yet!
Luckily - i dont think my oil pressure is actually too high nor too low, but from what ive gathered around people around me, oil pressure is important specially in rotary. i just want that peace of mind ... im already anxious enough learning manual in this thing
In that second pic of the factory oil pressure sender, pull the wire off the send and use another piece of wire with striped on both ends. Put one end in the clear/milky connector and touch the other to bare metal or the negative battery terminal. The gauge should not move. What we're doing to try to see if the issue is the gauge or the sender. It's more than lickey the sender.
https://www.rx7club.com/new-member-r...rking-1084016/
"The expected value range is infinity (gauge at 0), to ~100ohms (gauge max). Any lower value (such as a dead short) or a value that doesn't match up with what you're expecting would indicate a problem before the gauge."
In that second pic of the factory oil pressure sender, pull the wire off the send and use another piece of wire with striped on both ends. Put one end in the clear/milky connector and touch the other to bare metal or the negative battery terminal. The gauge should not move. What we're doing to try to see if the issue is the gauge or the sender. It's more than lickey the sender.
https://www.rx7club.com/new-member-r...rking-1084016/
"The expected value range is infinity (gauge at 0), to ~100ohms (gauge max). Any lower value (such as a dead short) or a value that doesn't match up with what you're expecting would indicate a problem before the gauge."
i tried grounding it and the reading still read gauge max 😔 unless im grounding it wrong but i tried different spots just in case and still same reading of max
With the wire disconnected, it should read zero. See what it goes to zero with that connector disconnected and not hooked to anything.
I hate to condemn the sensor just yet. It's sounding more like the actual gauge in the cluster. I can send you a used factory oil pressure/volts gauge for the price of shipping if you want to give that a try. It's a pain for a newer person the remove the gauge cluster. I hate doing it myself. The other option is to get an electrical gauge. I like the iEquess electrical oil pressure gauge myself. https://www.iequus.com/8243.html
Last edited by KansasCityREPU; Apr 17, 2025 at 09:35 AM.
Just took a quick sneak peek on my other 12a, looks like there was some aftermarket oil pedestal on there but the stock oil pressure gauge unit is there. I think im just gonna get the racing beat oil pedestal to have both an aftermarket oil temp and pressure gauge.
There are really only 3 parts; the Gauge (*in the dash), the Oil Pressure Sending Unit (*the 'mushroom' on the rear iron), and the wiring in between. You keep using the terms interchangeably, but it's far easier to unscrew the Oil Pressure Sending Unit and screw anoher one in, connect the wiring plug and see if it's fixed. More than likely, the Sending Unit has gone bad. It happens, particularly when sediment or oil residue gets caked up in the diaphragm or the pressure port and prevents easy flow in and out of the Sending Unit. The single-wire connector compares the signal to ground at the Gauge and then shows as needle movement.
You could try removing the Oil Pressure Sending Unit and cleaning out the pressure port from the engine side. Sometimes soaking in acetone or denatured alcohol will clean it out enough to work correctly again. Replacements are plentiful, as they were used in many cars of the era.
Duplicate gauges, senders and wet troubleshooting gauges are a fool's errand unless this is a track car. One man's opinion,
There are really only 3 parts; the Gauge (*in the dash), the Oil Pressure Sending Unit (*the 'mushroom' on the rear iron), and the wiring in between. You keep using the terms interchangeably, but it's far easier to unscrew the Oil Pressure Sending Unit and screw anoher one in, connect the wiring plug and see if it's fixed. More than likely, the Sending Unit has gone bad. It happens, particularly when sediment or oil residue gets caked up in the diaphragm or the pressure port and prevents easy flow in and out of the Sending Unit. The single-wire connector compares the signal to ground at the Gauge and then shows as needle movement.
You could try removing the Oil Pressure Sending Unit and cleaning out the pressure port from the engine side. Sometimes soaking in acetone or denatured alcohol will clean it out enough to work correctly again. Replacements are plentiful, as they were used in many cars of the era.
Duplicate gauges, senders and wet troubleshooting gauges are a fool's errand unless this is a track car. One man's opinion,
Fair opinion honestly, I dont blame ya.
okay so… i was moving too fast and careless lol but I pulled off the sending unit from the other 12a, and it still read gauge max, and in the process of doing that, i broke my water temp sensor that’s close to it. So ill run the mechanical for now until I get the electric gauge sorted out.
also blanked out and started the car with the sending unit out. Anyways ill be making a home depot stop and report back
better to move the engine wiring harnesses a little bit and have someone watch the gauge, it's more likely your harness has rubbed through and is shorting out somewhere to ground. by replacing the sensor and disconnecting it you have already ruled out the end of the circuit, it's time to move on to the middle bits and other end.
you could alternatively move to the other end of the circuit. pull the cluster and measure resistance of the wire to the oil pressure gauge to ground with the oil pressure sensor disconnected, it should be open and show no resistance whatsoever, if it shows open it's possible your gauge went on vacation.
engine harnesses are supposed to be secured but often times people just lay them wherever they feel like, the movement of the engine and heat eventually melts or wears the insulation off wires. i have even seen wires melt together to form a huge clump inside wiring harnesses before, usually when oil is introduced into the loom along with severe engine heat.
Last edited by notanymore; Apr 22, 2025 at 01:17 PM.
I did try cleaning the connector and the unit a little bit and started the car again and that seemed to fix it, until I started the car again and it's back to reading max. So im making a quick stop to the store to get some alcohol to actually clean the contacts in the meantime.
