G5 with GAD 13 woes

Help (Steve? )

I have a brand new G5 installation with GMU 11 and GAD 13, wired as the book shows, with G5 at one end and GMU 11 at other with Gad 13 wired in between.

Everything appears to be happy can bus wise, but with the Davtron C307PS on pins 4 and 5 I get nothing. Well, I get the red X on pfd screen and get INVALID on the diag screen.

Power out on pin 5 to white ?+? on probe. Return on 4 from white/blue on probe. Probe shield is connected (grounded) through connection at Shell and I verified ground lug on probe (mounted in plastic cover) has continuity to ac ground.

I had one slightly unseated pin on my GMU 11 install, so I?ve checked and double checked all that...now I?m just about to lose my mind. I bought the factory Davtron probe because I didn?t want to frustrate myself with fabricating one!

Thanks for any thoughts you guys have!

Well, so much for RTFM?

I don’t get it, but in cutting everything back to make sure nothing was shorted or a problem where I soldered to the braided shield...I decided to try without the shield wire connected/grounded. BAM. 49 OAT which unfortunately matches my thermostat because I ran out of propane last night, apparently.

So, do I just ignore this right off the data Sheet? I know I’m not the smartest guy, but this seemed like a pretty direct instruction. GAD 13 is grounded by mounting, clamshell connects to it, therefore grounded, and that’s where the drain wire goes...I thought.

Anyway, it IS working. Hmmmm?


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punkin said:

I don?t get it, but in cutting everything back to make sure nothing was shorted or a problem where I soldered to the braided shield...I decided to try without the shield wire connected/grounded. BAM. 49 OAT which unfortunately matches my thermostat because I ran out of propane last night, apparently.

So, do I just ignore this right off the data Sheet? I know I?m not the smartest guy, but this seemed like a pretty direct instruction. GAD 13 is grounded by mounting, clamshell connects to it, therefore grounded, and that?s where the drain wire goes...I thought.

Anyway, it IS working. Hmmmm?

Click to expand...

Hello Scott,

The shield on your temperature probe should not be shorted to one of the two signal wires. Based on their note, they don't think it should be either.

You should make sure that your solder connection to the shield didn't some how short the shield to one of the wires, but otherwise it seems like maybe a bad probe.

One small shield braid wire piercing the insulation on a signal wire it all it takes. We sometimes hear from customers who have managed to get a shield braid short to a signal wire under a solder sleeve.

Thanks,
Steve

It?s not!

According to a continuity test anyway?that?s what I checked to be sure of...I guess I wasn?t clear...I wasn?t checking to make sure it WAS, I was making sure it wasn?t...It?s always a fear to me on tiny wires when I heat up the shield braid enough to solder that I?d melt or poke through...But it was fine.

Disconnecting the shield ground seems to have everything playing nicely. I reread?yup Gad 13 is SUPPOSED TO BE (and is) electrically bonded...and probe shield is supposed to be. But it pukes it out.

Even if the factory connection side was shorted to one of the signal wires it would show up with continuity testing...hrmmm

But with the shield ungrounded all seems right with the world? Leave it alone?

Checking the ground lug on the probe it?s open (as it should be, one end isn?t connected to anything). But I?ve getting valid OAT now...?

GAD 13 Connection Diagram

Here is how I wired my Davtron OAT probe. Since the OAT probe was installed in a hole in aluminum skin the probe end was properly bonded to the airframe. On the GAD 13 end I grounded the shielding to the backshell of the connector with a solder sleeve shield drain wire, just like you do with the CAN Bus wires. Also, the GAD 13 (like the GAD 29) is supposed to have it's chasis grounded to the airframe which is usually taken care of with the attaching screws. However, my GAD 13 is suspended from two Adel clamps so the rubber clamp cushions don't allow the GAD 13 to bond to the airframe. So I bonded it with a 16 gauge jumper wire as per the instructions.

Seems to work just fine with the probe wire shield draining into the backshell.