• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • Hey! Be sure to login or register!

CHT showing nothing. Trying to troubleshoot

Tick

Registered User
Anchorage
OK, so let me start out by saying I have spent nearly $3k in various repairs on my bird in the last 30 days so I'm pretty financially tapped out. I'm trying to self-diagnose before I help my A&P make his next mortgage payment.

I've got a 1953 PA-18A with an O-320-A "narrow deck" 150hp. The Alcor CHT (46151) has just mysteriously stopped working altogether shortly after having a new digital Electronic Instruments digital tach installed. The needle just sits full left like the engine is cold all the time when it should be reading well into the 300 degree F range in my experience.

I tried to trouble shoot by looking for any loose connections from the back of the CHT guage all the way to the probe and everything was in great condition and no connections were even remotely loose. I took a heat gun to the CHT probe set to 500 deg F and nothing happened.

I'm handy but not particularly skilled in electrical work. Any help trying to diagnose the likely culprit would be greatly appreciated. I've attached some pictures of the probe as well.

20200614_203849[1].jpg

20200614_203826[1].jpg
 

Attachments

  • 20200614_203849[1].jpg
    20200614_203849[1].jpg
    109.9 KB · Views: 124
  • 20200614_203826[1].jpg
    20200614_203826[1].jpg
    82.7 KB · Views: 101
Disconnect the wires from the back of the gauge. Connect a digital voltmeter to the wires and heat the probe. You should see a rise in voltage as the temp increases. It sounds like you have a broken wire someplace.

Web
 
I had a malfunctioning CHT gauge a while back.
Gauge & probe are both UMA.
I read what little troubleshooting info they had,
testing with my ohmmeter indicated the gauge was the problem so I ordered a new one.
Tested the new gauge when I arrived, and it tested out exactly the same.
Installed it anyway, everything worked then.
Wierd.
 
Back
Top