Electric fuel pressure gauge

I am replacing the fuel pressure gauge on my Aeropro A-220 which is direct reading with a new UL Flightline electric gauge and sender. Does anyone have a wiring schematic for this gauge?
Regards
Mike

Mike,
I'm trying to figure this out now myself. Did you crack the code? If I send power to both the sender and gauge, the gauge self tests then it just pegs at max pressure. If I remove power from the sender and turn on the boost pump, I get a live gauge but no pressure indication. The ROAD tech data is no help.
thanks
Jim

You will need to be more specific.
What are the part numbers of the Gauge and the Sender?
What documentation was supplied?

Bill,
This is the UL Flightline (ROAD) Fuel Pressure gauge mfr. model number IE71.2B35.2201 that uses a Delphi three-wire harness 54KO.1000.0019 connected to sensor P906.B001.OS. I have the sensor installed in the fuel manifold of my 912UL and the wire harness routed to the gauge, which has four tabs, three are clearly marked to accept the three wires from the sensor. The fourth gauge tab is to accept input for illumination dimming according to the gauge tech data sheet. What I want to know is where to connect 12v to the gauge? Thanks! Jim

The documentation is sketchy at best, but let me take a shot at it.
What you have is a 0-15psi (1bar) pressure gauge.
The signal from the sender is 0.5 to 4.5volts,
The cable is 3 wires. Red, Green, Yellow.

An educated guess...
The RED wire from the sender connects to the (+) terminal of the gauge AND the Battery +12v
The GREEN wire from the sender connects to the (-) terminal of the gauge AND the Battery Ground (-).
The YELLOW wire from the sender connects to the (S) terminal of the gauge.

If you have any documentation that indicates the color coding is different, follow your document and ignore me.

Thanks Bill. No, there is no documentation I can find other than the tech drawings that don’t show me how to wire the gauge.. I tried a piggyback power connector on the + tab on the gauge that fed 12 volts to both the sender and the gauge, but all that got me was a full pegged indicator (greater than 15 psi). I’ll keep at it until I win.

The problem is that the wiring harness uses non-standard colors and it is anyone's guess which way they connect.
There are 6 ways to connect 3 wires and 5 of them are wrong!

I believe you have a Delphi GT-150 Connector.
The only thing that may save us is that even though the voltage and signaling colors may vary, the Power and Signal position on the connector is usually consistent.

Try using this photo to determine which colored wire goes to which pin.
Keep in mind that even though the wire enters connector on the left, it does not necessarily connect to the Left pin internally. Use an Ohm-Meter to verify the connections.

Also, remember that the photo is of the Sensor.
The connector on the Wire harness will be a mirror image.



There is a standard in the sensor world where...
Brown = Power
Blue = Ground
Black = Signal
But this isn't the case here. These people are nuts!

Good information, thanks. So the sensor would receive 12V (from the gauge?) and output 0.5 to 4.5V depending on fuel pressure? Or I wonder if the sensor, which has a drilled chamber to accept fuel flow, is actually a transducer that needs no power input but instead converts mechanical motion (caused by fuel pressure) to a voltage input to the gauge? Alas my inquiring mind will have to wait until this coming weekend to learn more.

The sensor has a single opening so there is no "Flow", only Pressure to a dead end "Chamber".
The Sensor requires Power (12 Volts) in order to operate its internal electronics and output the 0.5 to 4.5-volt signal in proportion to the pressure.
The three wires on the sensor are 12volts, Ground, and Signal.
The question that needs to be answered is, "Which color Wire is attached to which Pin?".

Well the “three wire” harness arrived and just to make things sportier for me, it has three female pins at the sensor end- and four wires peeking out from the sheathing at the gauge end.

STOLCH701 wrote: Well the “three wire” harness arrived ...

Now I am confused!
I thought you had already tried to wire the gauge and could not get it to work???

You may be looking at Three wires plus a Shield.
What colors are the wires?

Bill,
No shield. Here is the pin out for the expensive precision German ROAD harness for connection from the sensor to their fuel pressure gauge. Black is + (power), Green is Sensor (.05 - 4.5VDC voltage input to the gauge from the sensor), and Red is ground. I’m Not making this up. Verified this at the gauge. There is a fourth (yellow) wire in the “three wire” harness that has no continuity to anything else in the harness. At least on the harness I received from Aircraft Spruce. Using a 1.5V AA battery rig I finally determined the the gauge is fine, the problem is with the never flown $147 sensor. Peeking inside, I see that the sensor chamber piston that should move in and out with fuel pressure is jammed full in and thus the sensor is continuously transmitting the full 4.5V to the gauge, My attempts to free it bore no fruit. So despite the fact there’s no fuel pressure at the manifold, the gauge reads max pressure. I spoke with Aircraft Spruce and requested a no cost replacement (fingers crossed) and a chance to speak with anyone from ROAD but I doubt anything will some of that. ROAD is in Deutschland and to date they’ve ignored my independent email inquiries.

STOLCH701 wrote: ... Black is + (power), ... and Red is ground. I’m Not making this up...

I don't mean to question your results. ... OK, Yes I do!
Did you remember that the picture was of the Sensor and so the Connector/Harness is going to be a mirror image that reverses the Black and Red? Red= Power. Black = Ground. ???

Just checking because I can't see what you see.

I am surprised that you took the sensor apart.
I am also surprised that there is a moving piston!
I would have assumed it was a strain gauge with No moving parts.
Are you sure you're sure?

Seeing how you have already decided the sender is scrap.
Try reversing the Red and Black power leads from the Sender. RED(+) BLK(-)
You have nothing to lose.

Bill
No worries! I appreciate your feedback and don’t mind you questioning my troubleshooting at all. At one point I had the sensor on my lap, plugged into the harness, as I sat in the aircraft. I had the gauge out of the instrument panel but connected to aircraft bus power and the aircraft ground bus. Using the unterminated gauge harness wires as test leads, I had the black harness wire connected to the gauge + terminal, the red harness wire connected to the gauge - terminal, but no other harness wires touching the gauge. I then put 1.5V directly to the gauge S terminal (bypassing the harness) using the AA battery I rigged, and for the first time, the gauge indicated a PSI less than pegged beyond max. At that point I put my multimeter test leads on the Green harness sensor output wire and aircraft ground, and I saw 5 volts on my meter. The max output to the gauge should be 4.5v. I will try reversing the power and ground wires to the sensor and measure the output from the sensor.

Bill
Yup you were correct I had the red and black wires reversed. Unfortunately it made no difference, the sender is locked down on sending 5VDC and still pegs the gauge at max psi despite the fact there is no pressure at the manifold.

STOLCH701 wrote: Well the “three wire” harness arrived and just to make things sportier for me, it has three female pins at the sensor end- and four wires peeking out from the sheathing at the gauge end.

That makes sense per your previous post. three wires at the sender and a fourth at the gauge for the night light.

STOLCH701 wrote: Bill
Yup, you were correct I had the red and black wires reversed. Unfortunately, it made no difference, the sender is locked down on sending 5VDC and still pegs the gauge at max psi despite the fact there is no pressure at the manifold.

Well, that's a bummer!
I would have hoped that the sender had reverse power protection.
I may be that you smoked the sender by hooking it up with the power leads reversed.

Sometimes it does not matter with DC but that’s possible. I would think a 99 cent diode would be part of the design of the sender. I’ve returned it and I have another one on order.