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  #1  
Old 09-07-2021, 04:07 PM
SR2500 SR2500 is offline
 
Join Date: Apr 2011
Location: Colorado
Posts: 156
Default CHT problem

VM1000C gold box. O-540 lycoming. At Oshkosh, my rpm sensor failed. So I ordered a new one, new EGT probes and new CHT probes as a couple had stopped working. Now, rpm is good. EGT is good. CHT is good with master power switch on, but when the engine is running they revert to What appears to be OAT. Any thoughts?
Jerry
Probes are Dynon J probes, bayonet style.
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Jerry Folkerts
Pietenpol, built and sold
Cygnet SF-2A, built and sold
Cygnet SF-2A, refurbished and sold
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Vans, next build
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  #2  
Old 09-07-2021, 07:33 PM
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azrv6 azrv6 is offline
 
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Jerry, do you know the age of the battery chip? In my experience, the VM system can start to act flakey as the battery chip approaches end of life.

Reggies article on this:
https://vansairforce.net/community/s...ad.php?t=84322
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Dave Binkley
RV-6, O-360-A1A, C/S
1932 Monocoupe 110, Warner 145 (http://gobinkley.com)
Sedona, AZ
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  #3  
Old 09-07-2021, 07:48 PM
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azrv6 azrv6 is offline
 
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Another thing you might consider are the real time processing chips:

https://vansairforce.net/community/s...d.php?t=115116
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Dave Binkley
RV-6, O-360-A1A, C/S
1932 Monocoupe 110, Warner 145 (http://gobinkley.com)
Sedona, AZ
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  #4  
Old 09-08-2021, 06:18 AM
SR2500 SR2500 is offline
 
Join Date: Apr 2011
Location: Colorado
Posts: 156
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Thanks. Iíve got an email in to Reggie. I did split the box to replace the battery. Hopefully I didnít introduce a stray tron.
Jerry
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Jerry Folkerts
Pietenpol, built and sold
Cygnet SF-2A, built and sold
Cygnet SF-2A, refurbished and sold
Murphy Super Rebel, built and flying
The Pedal RV, designed and built
Vans, next build
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  #5  
Old 09-11-2021, 04:52 PM
SR2500 SR2500 is offline
 
Join Date: Apr 2011
Location: Colorado
Posts: 156
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Problem solved. I had to go to the probe manufacturers to figure it out. VM1000C used an ungrounded J probe. The Dynons I replaced them with were grounded probes. Evidently, there are a few older systems out there that amplify the signal to make it work and the grounded probes interfere with this. There’s a good discussion about this on the Alcor website. Finally, I verified this with Reggie who still helps out with the VM product line.

You can replace a grounded probe with an ungrounded one, but not vice versa.

Consequently, I have six new Dynon CHT bayonet type J probes. I paid $38 each from Stein. Will sell for $25 each plus shipping. I’d rather not separate the batch.

Jerry
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Jerry Folkerts
Pietenpol, built and sold
Cygnet SF-2A, built and sold
Cygnet SF-2A, refurbished and sold
Murphy Super Rebel, built and flying
The Pedal RV, designed and built
Vans, next build

Last edited by SR2500 : 09-11-2021 at 05:00 PM.
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  #6  
Old 09-11-2021, 05:17 PM
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azrv6 azrv6 is offline
 
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Thanks for closing the loop, and the useful info. Glad to hear Reggie is answering questions again.
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RV-6, O-360-A1A, C/S
1932 Monocoupe 110, Warner 145 (http://gobinkley.com)
Sedona, AZ
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