OG GarlicSalt

Thanks Mark! Nope FIM never suggests the panel itself and jumping the pins just my idea to double confirm the finding. FiM just general wiring issue from P33 to panel.

Working on a 767-200 pilot reported that the #2 ACMP is INOP while in auto mode but working properly when switched to on. 

First thing I did was just a normal ops check right away when switched to auto the pressure light comes on and we never get any pressure. When switched to ON full pressure and no issues using the hydraulics.

First step was to check out a few of the relays and time delay on the auto side and see if we are getting any power. The relays and time delays are all in the P33 in the MEC so easy trouble shooting all in one place. 

 
 
 


So had an odd findings everywhere that im expecting to see 28v im seeing 1v-3v so way way low. Just to be sure of myself i replaced k126 and k128 relays with new since already available in my hand. No help and still getting the low readings at both relays and time delay module. So smelled like high resistance, actually if you reference the fuel section on this forum you will see 767 will fuel cutoff switch having high ohm reading. I worked on that job with Mark a few years back and thats what lead me to try the switch right away. 

Found that the switch reads extremely high ohms sometimes open while in the auto position and .5 ohms while in the ON position.

 

I then decided to jump pins 8-12 so bypass the switch and see if the pump would operate as normal just to fully verify the switch as the problem. Luckily while jumped everything is working as it is supposed to.

 




Considering this to be isolated parts on order and hopefully MEL cleared soon!
 

Thanks Mark! We have been looking for a cheaper 429 reader + software. Will look into this for our department, have you tried the transmiting function?

Mark,

There is actually a much better version of this document. ABX avionics engineers made a document like this but has the photo of each light in the chart and all PN for LED and Filament. Ask them to share it to you or send me your personal email and i can share to you.

Working on a Boeing 767-200 pilot reported LH WXR would not pass the test mode when selected to LH side.

They found that when selected to LH side that LH WXR RT would be stuck into a boot loop, just showing the main screen and as soon as it finished or almost finished it would do it over and over again no way to BITE the box.

I started on this project late the other guys spent about a week trying to track down the issue. 

When i started working this already they had

Swapped LH & RH RT
Replaced Wave Guide S/W
Replaced WXR Control panel

With the LRU having these weird issues it smelled like a wiring issue to me.

So when i started to work on this based on the last guys diagnosis I started at the wave guide S/W. I found out that with LH WXR selected whenever you unplug the waveguide S/W that the box will boot up and you can perform the BITE test but it just shows Wave Guide S/W since its disconnected so no help from the box nothing in the fault memory to help either. So what I decided to do next was make a jumper harness and try to isolate some of the wiring to see if i can find out what is causing the problem from the wave guide plug.

 

After trying many different configurations of wiring I find that the only time the fault on the box is present is when PIN A and C are both connected. Next thing I decided to do was just straight jumper pin A-C when connected the box went back into its reboot cycle. This told me that wave guide its self is for sure good because issue still present when bypassed. So what I have decided is that this is most probably an issue coming from the A wire.

 

So at this point i rang out the wiring from the controller to waveguide and to the RT and from the wave guide to RT rack all checked good. I also double checked the wire from controller to wave guide and waveguide to RT rack with megger just to be sure. To this point everything had checked good. So next thing i did was ring out all the data bus and control bus wiring to the RT. Im thinking that maybe im to hung up on the A wire and maybe when the signal to activate comes in from the controller something else in the box is changing, the symptoms on the box are similar to ones you might see that have shorts to shield or ground. Everything checks good, at this point i would have changed the WXR control panel but already done so I had to dig deeper.

After checking the system Schematic manual I found out that wire a goes to the controller then back to the RT when in LH mode and to ground when in RH mode. The signal coming in comes from the antenna drive, so next stop was the ATT.

 

When i got to the antenna i unplugged the LH output from the ATT drive went back to the LRU and finally the box had stop rebooting.

 

Next thing i did to verify everything down stream was to plug back into the att drive and then swap the output connectors at the bulkhead. I would have completely changed the harness over but due to the back shell it didnt have clearance to fit past the wave guide.

 

After swapping the output plugs LH side is passing the test and RH side failed the test. So has to be the antenna drive or the wiring harness from bulkhead to antenna. I decided to ring out the wiring harness from the bulkead to the radar and everything checked good. Did learn something new though a lettered 55 pin plug never have come across a plug labled like this before so luckily i was able to find a diagram so I could read it.

 


Ring out checked good, radar drive replaced and finally DMI cleared. Probably wasted a lot of time ringing wires but the problem at the box was so odd that it had me thrown off. You would think that the LRU would be able to interrogate and identify a hardware problem in the antenna without having this rebooting issue. My only thought is when we removed the old drive assy we found some corrosion on the very small wiring so possibly something short within the assy that is sending a bad signal to box causing the rebooting issue.