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  #1  
Old 11-25-2020, 11:27 AM
ShortSnorter ShortSnorter is online now
 
Join Date: Dec 2013
Location: NOLA
Posts: 255
Default Kavlico P4055-30A (MP Sensor) Troubleshooting

I've googled this site and found bits and pieces of information I'm looking for, and spoke with the G3X folks this morning to try and turn over a few more rocks. Ultimately here's a brief description of the problem:

- Kavlico P4055-30A
- Measuring ~5v on both the red and green terminals of the sensor plug (unplugged) while grounded to both the black terminal plug or the airframe
- Gauge stuck at 29.7 as displayed on the GDU
- I uninstalled the sensor and checked for any debris in the sensor orifice
- Display range max of 32"
- The reading of 29.7" displayed has not moved with the recent changes in local weather conditions
- 30.08 - 30.05: delta ranging from 0.38 - 0.35

I updated the software on the GDU to v 8.72 which did not change anything with the MP indication. I verified that the GEA 24 is on software v 3.7 after the GDU update.

Are there any other considerations other than to try a new sensor even though this is a new installation? It is my understanding that there is a .3 tolerance delta for the sensor, but I would be interested in understanding other comparable installations & how they compare with local weather conditions and static MP as measured by the sensor.
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  #2  
Old 11-26-2020, 07:09 AM
ShortSnorter ShortSnorter is online now
 
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Default More data

I did some additional testing by swapping +/- into the plug along with the signal wire and got displayed reading from 8.0" all the way to 56.4"

I'm not sure this really helped with trouble shooting other than to see a response when different wires were crossed.

I still keep going back to how accurate are these sensors really? I don't have any experience with digital MP gauges so the granularity they provide may be throwing me off.
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  #3  
Old 11-26-2020, 08:35 AM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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I would expect an accuracy in the neighborhood of +/- .5 to 1". I would wire it back up correctly, put a hose on the end and suck on it and observe the reading. If it shows 29" at a steady state and while drawing a vacuum, there is a pretty good chance that the sensor is defective. The fact that you get a 29" reading now, indicates no issues with wiring or the G3X. The inaccuracy should scale, so I would expect that a change in abient pressure of .4 would show at least a change of .3.

If accuracy is important to you, you can build a custom map in the G3X based upon actual, observed output from the sensor. That is what I did, as I used a GM sensor and the G3X doesn't have a table for that.

Larry
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Last edited by lr172 : 11-26-2020 at 08:49 AM.
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  #4  
Old 11-26-2020, 09:06 AM
ShortSnorter ShortSnorter is online now
 
Join Date: Dec 2013
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Quote:
Originally Posted by lr172 View Post
I would expect an accuracy in the neighborhood of +/- .5 to 1". I would wire it back up correctly, put a hose on the end and suck on it and observe the reading. If it shows 29" at a steady state and while drawing a vacuum, there is a pretty good chance that the sensor is defective. The fact that you get a 29" reading now, indicates no issues with wiring or the G3X. The inaccuracy should scale, so I would expect that a change in abient pressure of .4 would show at least a change of .3.

If accuracy is important to you, you can build a custom map in the G3X based upon actual, observed output from the sensor. That is what I did, as I used a GM sensor and the G3X doesn't have a table for that.

Larry
Forgoing the whole great minds think alike - I actually just walked in from the shop and tried that, and guess what? It responded perfectly!

I really starting thinking about conventional knowledge & manifold pressure "reading ambient" when the engine is off & the fact that there was no way that traditional steam gauges could provide the granularity I was hung up on. Though unscientific, I browsed 5 or so builder's sites and noticed much larger discrepancies than I have in manifold pressure and current altimeter settings (granted they may not have had the current setting dialed in). Anyhow, time to bundle everything back up and press on. I guess the last day spent chasing a ghost can be chalked up to the whole learning experience that we call building.
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