How should i ground my oil temp. sender?
 

I have my autometer oil temperature sender mounted inside a mishimoto oil filter spacer back when I needed a oil feed for my turbo (99 block). Now that I am using a 94 block with the supply port on the driver's side, I have nothing else installed in the spacer. I have been wondering why my oil temp. gauge isn't reading anything, and I think its because now it is fully insulated from the engine. The oil filter spacer has an o-ring where it mates to the block and the oil filter has an o-ring on it. (obviously)

Has anyone had this problem or does everyone tap into the pan/oil drain?

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Send it to bed without dinner.

Do I read it a bedtime story too?

Seems the easy thing would just be to drill and tap a small hole into the body of the spacer for, say, a #10 screw, and then use that to secure a ring terminal to the body, like this one:

https://www.miataturbo.net/attachmen...ine=1462838831

Thence, a short wire secured somewhere to the block (try to keep it away from the alternator), and you're good.

Have you verified connectivity between sender housing and ground with a voltmeter? If it has contact, ground is not your problem.

^ Excellent point.

I'll try this first, thanks.

Good idea, I was thinking about taking the sender out, and tapping a ring terminal to the size of the sender and threading it onto it.

Assuming that the sensor is threaded NPT, it's highly unlikely that the sensor body is bottoming out against the sandwich plate. Thus, you won't get a solid connection by sandwiching a terminal between the sensor and the plate.

I see your point, but if it is not bottoming out, wouldn't I be able to grind/cut a 1/8 brass nut and use that to clamp it to the adapter? The current would then flow out the sensor, through the brass nut, connector, and to earth

This is what I did. Solved world hunger the next day.

I can't find a picture. But I hose clamped a spade terminal to the body of my sender. It worked great.

Where ever did you get THAT idea? ;)

Wish I read this 24 hours ago. My car is already on the ground. I'll do that next time it's up.

What Autometer gauge are you using? I would guess that it is the half sweep one that uses the sensor probe with a ground terminal on the end? If you are running the full sweep oil temp gauge, it uses a secondary ground. I used the same connector Joe pointed out adding it to the grounding strap near the oil dipstick (04 MSM). I ran that ground wire through the firewall and used it as the ground for both my oil and water temp gauges.

Aidan's solution is the simplest for the sensor that usually grounds to the engine. One thing to point out, the autometer sensors are usually NPT threading whereas I was under the impression the threaded ports on the miata for oil are BSP. If that is the case you need to add an adapter to make sure you don't introduce a leak.

The ground path should be:

1. Engine block => Adapter through threaded oil feed thingy;
2. Adapter => Sender through pipe threads.

#1 is the problem due to anodizing. #2 is usually good because the hole gets threaded after anodizing (you should double check). Next time you change your oil, pull the adapter off and hit the area around the center hole with a dremel wire brush attachment to remove the anodizing in that area. It will solve your issue.

I was losing ground because gaskets on both sides. Lots of gaskets. So I did this:

https://www.miataturbo.net/attachmen...ine=1463058488

Yes it is a half sweep.
I think i managed a solution. I found a large diameter ring terminal to fit into the sender, and sandwiched that between 2 stainless steel washers. Tied that to a ground and should work. Haven't started it because I'm working on wiring ebc into the evap purge lines.