<p>I want one of those.</p><p>Is your gauge grounded to the block?</p>

Yep, gauges grounded to the block with a dedicated ground wire. I had it grounded to the intake manifold but moved it to the block just to see what happened. Nothing happened.

Yes, you should have it switched via the ignition switch. Source should be the battery however. A relay can easily be used to switch the power via the ignition switch.

Question: Are your temp sensors really 1 wire?

Yes

https://www.miataturbo.net/attachmen...ine=1438197852

Oh, well, forget what I posted about the wiring then. That sensor grounds to whatever it's installed into it appears. Thus you can't control ground loops when you install more than 1 sensor since they will ground into different places.

EDIT: To the OP, just disconnect the sensor that's working, and drive the car. See if the other sensor all of a sudden works fine. If so, that confirms you have a ground loop that you can't remove by having the sensors installed on 2 different ground planes.

<p>Small update. Grounded the Oil Temp Sensor like this:</p><p>Attachment 232948</p><p>And it kinda worked. It works great for a while, but on long drives, or the end of sessions sometimes the gauges go crazy like this:</p><p> </p>

<p>VEI is having me wire resistors into the gauge instead of temp senders. Then run it for a while. This will tell me if there is an issue with the gauge or the sensors.</p><p>I wish they would just send me another one, but oh well.</p>

Gesso pumped up my OPG sender with a bike pump to about 70psi and then we watched the ohm meter while it slowly leaked down via an 'engineered leak' in the test rig. Many :rofl: :vash: & :facepalm: were had by all involved.

We may or may not have accidentally spun the contact stud in the sender before this happened, but the display behavior has not changed. Lolwut?

<p>Did it work? The sender I mean.</p>

Kinda. We should have taken a video, there is a huge section of the range where the signal was all over the place. There must be some pretty massive damping on the input channel for it to display any kind of consistently.

<p>You mean like in the video above :) &nbsp;Maybe that is the real signal.</p>

Well plus side to that is it's actually testing something to isolate the problem.

You could also try my test of unplugging one to see if a ground loop is the problem. Again this will help isolate what's causing this. You know you have a problem, but you don't know what is causing it.

<p>They are being helpful and working through the problem with me. Before I try that though I am going to put the gauge ground on the head where the other senders ground just in case thats the issue. Mostly because it is easier to do than rewiring all the sensors.</p>