Quick Jump Menu
Info Ask a Question
Advanced Search Search the Knowledgebase
 Featured
Grounding Instructions - Engine Senders and Probes Reading Incorrectly
Author: Matt Liknaitzky Reference Number: AA-00232 Views: 21255 Created: 2012-07-04 12:18 Last Updated: 2014-03-14 10:09 0 Rating/ Voters

If your Oil Pressure, Oil Temperature, CHT, EGT or RPM / Tach is reading incorrectly (low, high, intermittent), the very first thing to check is the Reference Ground to the Engine Block.

About 95% of all sender reading troubles are related to inadequate engine block Ground or total lack thereof.

Why is this important?

Many Engine Sensors use the Engine Block as the Ground return path. And, the Engine Block Ground can have a different Ground potential when compared to the Aircraft Ground Bus or Battery Negative. Therefore, if you do not Ground Correctly to the Engine Block this can have a significant effect on the sender measurements and can cause big indication errors. Most senders measure resistances or small voltages and these will be inaccurate or intermittent if there is not a Reference Ground to the Engine Block.

So, what needs to be connected to the Engine Block Ground?

The EFIS itself or the Single Instrument still needs to have a Supply Ground at the Avionics Ground Bus. However, The RDAC Ground (in cases where this is used) or the wires labelled Reference Ground (in Singles) need to be Grounded directly to the Engine Block.

What does DIRECTLY mean?

Directly means that the terminal needs to be wired DIRECTLY to the Engine Block Ground, with the shortest possible wire, WITHOUT first Grounding to Airframe or Battery Negative. Just a straight line to the Engine Block. Use heavy gauge wire (18 AWG or better) if possible.

Which wire is the Reference Ground?


Select your device:


IMPORTANT NOTICE: You must make your own determination if the products sold by MGL Avionics are safe and effective for your intended applications. MGL Avionics makes no representations or warranties as to either the suitability of any of the products we sell as to your particular application or the compatibility of any of the products we sell with other products you may buy from us or anywhere else, and we disclaim any warranties or representations that may otherwise arise by law. Also, we offer no specific advice on how to install any of the products we sell other than passing along anything that may have been provided to us by the manufacturer or other users. If you are in need of further information or guidance, please turn to the manufacturer, FAA Advisory Circulars and guidance materials, the Experimental Aircraft Association, or other reputable sources.