Oil pressure gauge maxed out
 

I've got an issue, hoping someone can help aim me before I really tear in. My OEM oil pressure gauge will read 0 with the key off. With the key on, it will read 120psi (aka max). With the key on, if I unhook the oil pressure sending unit the gauge will go back to zero. If I hook up the sending unit, back to maxed 120psi. I pulled the sending unit and tested it with my multimeter for ohms. Sitting in my lap, its ~90 ohms. I ran across someone who had spec'ed out the sending unit and near as I can tell from reading what they wrote 90 ohms should make the gauge read as low as possible, not as high as possible.

Any ideas before I go ripping into the gauge cluster area? I am a bit worried about pulling the gauge cluster area out considering all the brittle plastics, so dont want to jump in there if I dont have to.

Thanks for any help!

I know they're a little pricey at a $120 or so, but wouldn't it be worthwhile to just try a new sender?

Thats not a bad price given it gose bad about every 50k miles.

Its on my mind, but its the weekend and even if I order it now it'll be later this week before it arrives. Might as well research and ask now right?

I would strongly suspect the sensor itself. Go ahead and get a new one, they are a common failure item.

Dale

Welp, swapped out the sensor with a brand new one from Mazda, also got another gauge from ebay. Neither fixed my problem. Any other ideas? I am thinking perhaps some weird wiring issue somewhere? Assuming this is a 12v circuit, not a 5v? The back of the gauge should see 12v, Ground, and the sending unit signal, right? Planning to spend today wiring it with jumpers completely seperately from the cluster to see if this is a wiring issue or not. My odometer also seems to be blanked out too, which wasnt happening previously either

Bryan,

Since you noted the odo is blank I would recommend removing the instrument cluster to inspect your speedo circuit board. There are a few threads that cover its repair; you are welcome to check my relevant threads for it - specifically the part # thread. Turbo Blue's original "just got done figuring out how to fix an FD odometer" thread is the foundation.

After looking at the schematic you attached, part of the signal for the oil pressure routes through the Speedo board. It is worth inspecting the speedo board for leaked capacitors or other damaged components. Have you made any progress tracing the oil pressure wiring? When you installed the new pressure sender, did you measure it before and afterwards? How does the connector look at the sender? Lastly, have you done any work around the oil pressure sender before you noticed the abnormal gauge measurement?

As a side note, I pulled my instrument cluster to test another cluster and discovered 1 screw mount for the hood broke. I will attempt to repair it and reinforce the others with epoxy.

Cheers,
George