Wondering CHT gauge

[bradp]

Hi all 

I noticed my factory CHT gauge is wondering a bit.  What is the typical troubleshooting methodology?  Is this a matter of cleaning some contacts or do I have to start searching for an old type thermocouple?

FWIW it's a bayonette type gauge housed within the JPI probe (piggyback).  The JPI is reading fine.  

Thanks !

brad

[PTK]

It's wondering in torment in a regretful monologue "...to be...or not to be...that is the question...life was so wonderful on the green...why did I have to wander off that beautiful field of green?!" 

[Guest]

Start with the simple, check the connection on the thermocouple in the cylinder head and on the back of the gauge.  Then if needed the thermocouple is available from Spruce if it's a Rockchester.

Clarence

[cnoe]

The probe in my '78 J failed a couple of years ago. There was no wandering at all; it simply quit. Your issue looks more like a poor connection somewhere but could be internal to the probe. As Doc mentioned AS sells them (for only $112). https://www.aircraftspruce.com/catalog/inpages/rochcht.php


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[Yetti]

To the ire of everyone here, I would replace the ring terminal and solder it after crimping it.  I believe grounding out the wire should make the gauge peak.

Edited July 18, 2017 by Yetti

[Hank]

4 hours ago, Yetti said:

To the ire of everyone here, I would replace the ring terminal and solder it after crimping it.  I believe grounding out the wire should make the gauge peak.

My Oil Temp gage grounded out once, it pegged as soon as I turned on the Master switch--a dead giveaway.

[aaronk25]

Ya had same problem. Chased wiring and bayonet down ended up being the gauge. Tap on it when flying I bet you a crown and diet it wiggles. Probably gauge


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[bradp]

Loose connection seems to be it.  I just need to find a 4 mm wrench and I'll be all set. This nut is about the smallest I've encountered yet. 

[cnoe]

Loose connection seems to be it.  I just need to find a 4 mm wrench and I'll be all set. This nut is about the smallest I've encountered yet. 

Metric fastener on a MOONEY?!! OMG, the world IS ending! Look out west coasters, N Korea has LAUNCHED!!!


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[MyNameIsNobody]

Synchronicity?  What did it wonder?

[bradp]

It's probably a SAE but I measured it out with a micrometer on the mm scale just to confirm it's the smallest thing I've ever seen. 

[Hank]

It's probably 5/32" [3.97mm]. Mooneys are SAE all the way, unless it's something related to your engine monitor.

[lifendet]

On 7/18/2017 at 3:03 PM, aaronk25 said:

Ya had same problem. Chased wiring and bayonet down ended up being the gauge. Tap on it when flying I bet you a crown and diet it wiggles. Probably gauge


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Started having similar issue. Gauge settles mid point then eventually deflects to the right. I tapped on it and it did wiggle. Off the top of head anyone know the part number. It's for a 77 m20j. 

[jkb458]

On 7/18/2017 at 12:54 PM, Hank said:

My Oil Temp gage grounded out once, it pegged as soon as I turned on the Master switch--a dead giveaway.

My CHT gauge is pegging as soon as the Master is turned on. Gauge or bayonet probe?

 

Thanks in advance.

 

Jeff 

[Hank]

The safety wire from my oil filter was touching it, grounding it out. Rewired it properly, not touching, CHT gage immediately started working.

So I'd say you have a short somewhere. Follow the wires from the probe to the firewall, see if anything is touching it or if the insulation is broken, cracked, worn or missing. 

[jkb458]

Thanks! Will trace them down.