Oil temp gauge trouble shooting help

[billy hellcat]

Today I got out to plane to figure out what's going on with the oil temp gauge on the old engine cluster.   It has been intermittently maxed.  

Before I turned on any power it was low of course and then when I had my son turn the master on it read normal for the outside conditions.  I then wiggled the wires near the oil temp probe on the engine.  This immediately maxed out the temp gauge fullscale!  Then it just stayed in that position.  Power off temp  goes down then power on temp maxed out.  Trying this a few times occasionally the temp would indicate normal but anytime I touched those wires it would max.  What should I be replacing?  The whole probe and wiring ???  Or skip all that and add a new JPI oil probe to my jpi 700?  Thanks

[M20F]

1 hour ago, billy hellcat said:

Or skip all that and add a new JPI oil probe to my jpi 700?  Thanks

Personally if you got the cash a new probe and line would be the way to go into the 700. 
 
If you don’t have the $$ your situation sounds like a bad wire not the probe so would run new wires and see what happens. 

[MB65E]

The factory used knife connections in many places. Overtime they loosen up. 
attached pictures of my oil temp connection. I just replaced the connectors and butspliced the wires.
The landing gear relays were spliced in too. 
-Matt 

[N201MKTurbo]

Start by cleaning the connector. If that doesn't work, take the backshell off the Cannon plug for the temp probe and inspect the wires and soldering. If you have soldering skills, unsolder the wires, cut off 1/2 inch of wires and re-solder them in. The wires tend to fracture at the solder joints after 1/2 century of vibration.

[billy hellcat]

Thanks, I will try that.  I found that there is an oil temp probe connected to the JPI EDM that isn't hooked up.  Looks like it's just there waiting to be installed.  Why wouldn't it had been installed originally?  Anybody know how to install this.  My mechanic will do it.  Just wondering if anything has to be done to the edm700. Thanks

[Andy95W]

That looks suspiciously like the stock CHT probe for the old cluster.  Located where it is under the #3 cylinder make me think that also.  I’ll bet the previous owner got tired of his #3 CHT being significantly different from the others on the JPI so he installed another “normal” thermocouple and just Ty-wrapped the old probe where you see it.

[billy hellcat]

On 9/18/2023 at 1:12 PM, Andy95W said:

That looks suspiciously like the stock CHT probe for the old cluster.  Located where it is under the #3 cylinder make me think that also.  I’ll bet the previous owner got tired of his #3 CHT being significantly different from the others on the JPI so he installed another “normal” thermocouple and just Ty-wrapped the old probe where you see it.

You’re right that’s what it is I bet. That makes sense as well