Troubleshooting Oil Pressure - D120 & Honeywell

[dbonnar]

Lost oil pressure indication in flight.
Replaced Honeywell with new unit, same part #– still 0 lbs pressure indicated on the D120.
Removed and tested sender using bench pressure and got current on white wire varying with pressure (didn’t note exact values but it seemed to be behaving).
Continuity on red 12v (pin 15) wire checked from 37 pin head to connection at sender. 0 ohms resistance (good).
Measured 12v on same with switches on.
Resistance on white wire from pin 6 at 37 pin head to connection at sender is about 150 ohms.
----
So- sender testing OK; wiring testing OK.
Is there a chance that the D120 could have an internal failure for oil pressure only?
Is there a way I can test that (i.e. what voltage should I apply to pin 6 at run time to see any pressure reading > 0?
Thanks!

 

[dynonsupport]

Very unlikely that just the single input is bad. You might make sure that the Dsub pin for that input is fully engaged into the connector. Ie, are you actually getting signal into the EMS. To prove whether or not the EMS can read a connected sensor correctly: If you apply a voltage directly to the input pin: 2.9V or less is 0 PSI, 3.5V is 54, and 4.5V is 145 PSI

 

[dbonnar]

Outstanding - thanks. I also received your voice message and appreciate why people say Dynon support is the best. I'll double check the pin and the 200ohm resistor.

 

[stevelindell]

I had very unreliable pressure readings. Eventually ran a new signal wire with a new metal 200 ohm resistor to good ground and then into pin 6. Solved the problem. You might also have a bad crimp in the connector, I cut out the connector and soldered the 12v and signal wires directly to the Honeywell leads.

Steve

 

[dbonnar]

Thanks for the tips!  Yup - I can't crimp worth a darn so I have gotten in the habit of crimp & solder and check twice.  I verified that the pin male & female at the DB37 at least "look" good and are tight, and that I'm getting voltage on the female pin 6 when hot and about 200 ohms when not hot - -  so I'm ready to put the D120 on the bench with a stripped down test harness and try to move the oil pressure needle with a couple of 1.5 volt AAA batteries in series=3v. 

Question for Dynon tech: (is that you Mike?) -  - - - I know I need to apply power to the power and ground to the ground pins, but what other pins need to be dealt with to bench check my oil pressure?  i.e. Do I need to ground any pins or apply any loads to any pins in order to not burn out the D120?
Thanks-
.dxb

 

[dynonsupport]

Question for Dynon tech: (is that you Mike?) -  - - - I know I need to apply power to the power and ground to the ground pins, but what other pins need to be dealt with to bench check my oil pressure?  i.e. Do I need to ground any pins or apply any loads to any pins in order to not burn out the D120?
Thanks-
.dxb

(Mike from tech support isn't one of the posters here)

You need to replace the sensor wire with a voltage source, essentially. You still need the resistor to ground hooked up in the same way it is to the sensor.