737-800 window heat problem

This is a public forum for 737 maintenance related questions, requests and experience exchange discussions for every Boeing 737.


737-800 window heat problem

Postby Technar » 31 Aug 2017, 08:52

Hi friends,
I have urgent question. I had problem with the heating of the RH windshield. When the control switch is set to ON the idication for OVERHEATING illuminates immediately. I made BITE of the relevant WHCU and it gave TEMP SENSOR. I switched over to back-up sensor and made BITE again. This time it gave P5-9 PANEL/POWER CTR. I swapped the LH and RH WHCUs the fault stayed on RH. Then I swapped the P5-9 control panel with panel from another A/C-the same result. I didn't have ground time for further T/S.The question is why if the system is switched over to the back up sensor the BITE always gives P5-9 PANEL/POWER CTR? Obviously the problem is in the window or/and in the wiring. Probably this message P5-9 PANEL/POWER CTR when the system operates with the back up sensor means that this sensor is faulty also?
I will appriciate any information on the topic.
Technar
 
Posts: 9
Joined: 02 Nov 2013, 18:19

Re: 737-800 window heat problem

Postby maro12 » 31 Aug 2017, 21:54

Hello Technar,

Can You please confirm if after switching over to back-up sensor, during the BITE on WHCU the R FWD Window Heat Switch on P5-9 PNL was in ON position?

The message "P5-9 PANEL/POWER CTR" means there is no Control Power to WHCU, this power goes from CB through the switch on P5-9 to WHCU pin 5 (in FIM first step is to measure this power). This power will not be there if:

-CB is open,
-switch on P5-9 is OFF,
-wiring/connections faulty.

I went through the AMM, FIM instructions and actually I did not see clear step to put switch on P5-9 panel to ON for the BITE.

"P5-9/CONTROL POWER" -> "INDICATES NO WHCU CONTROL POWER due to open circuit breaker, control switch turned off (initiated BIT only), P5-9 failure, connector or wiring problems"

Best Regards,
maro12
maro12
 
Posts: 72
Joined: 05 Oct 2008, 01:51

Re: 737-800 window heat problem

Postby Technar » 01 Sep 2017, 18:46

Hallo maro12,
Yes the switch on the p5-9 was ON. On the last night shift colleague of mine checked the continiuty of the wiring between the WHCU and both window sensors. He confirmed that the normal sensor had open circuit but the back up sensor was OK. After that he switched on the system and everything was OK (operating with the back up sensor). i have no explanation why. The only thing he did was to remove the WHCU and to measure the resisance of the wiring from the shelf to the sensors. May be using jumpers cleaned the sockets of the shelf. For me it is compete mystery why the BITE gave me p5-9/power control fault when the sys was on the back up sensor.
Technar
 
Posts: 9
Joined: 02 Nov 2013, 18:19


Return to - 737 technical questions & requests -

Who is online

Users browsing this forum: Bing [Bot], Yahoo [Bot] and 1 guest

cron