b737800 air condition temperature indicator

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b737800 air condition temperature indicator

Postby WTB » 13 Jun 2017, 09:57

Greedings chaps,

we have a electrical problem with aircond. panel temperature indicator. When packs are off or on , temperature indicator show lower temperature in all positions(control cabin, pass zone, supply duct etc. )

the terrible thing is,

*when you push master caution, temperature indication drop, then after reset , it is normal.
* when you off the p5 panel brightness dim, it drops again . when you do fully bright, it shows normal.

all possible components are replaced. (panel, bulbs, indicators etc. )

have you ever faced this kind of snag? :roll:
b737-800 training - http://www.wingtobody.net
WTB
 
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Re: b737800 air condition temperature indicator

Postby Dunny » 13 Jun 2017, 16:14

sounds familiar....have you checked the bonding of the overhead P5 panel, in particular the strap that connects it to the fuselage frame.
Dunny
 
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Joined: 17 Feb 2007, 20:56

Re: b737800 air condition temperature indicator

Postby Dunny » 21 Jun 2017, 18:09

so what was the outcome ?
Dunny
 
Posts: 159
Joined: 17 Feb 2007, 20:56

Re: b737800 air condition temperature indicator

Postby yayoo » 01 Jul 2017, 04:12

Revision Description
Changed 0.001 ohm to 0.0035 ohm the Status and Operator Action sections.

Reason: The maximum resistance for a ground block to the structure to which it is attached is 0.001 ohms. For each bond interface, the resistance across the interface should not exceed 0.0005 ohms. Review of the ground path described in this FTD indicates 5 junctions; two jumpers, the junction between the drip shield support bracket to dripshield assembly and the ground block to structure. Therefore, maximum resistance from GD506 to primary structure should not exceed 0.0035 ohms.
Applicability
All 737-600/-700/-800/-900 airplanes
Description
Several operators have reported seeing the temperature indicator move when master caution is recalled, while the annunciator switch is being pressed. One operator has also reported the temperature indicator moving to zero when either air conditioning pack switch is placed in the HIGH position.
Background
During troubleshooting it was determined that high resistance between ground block GD506 and airplane structure can cause temperature indication to vary under certain conditions. There are several different ground types installed in GD506 which, when the resistance to ground is too high, will affect temperature indication.
Status
A quality investigation was accomplished in Boeing production where it was determined that, in some cases, the resistance of the ground path from ground block GD506 to the airplane structure is higher than 0.0035 ohm. Personnel have been advised to make sure the bonding instruction on the installation drawings are followed.
Interim Action
None
Final Action
As described in Status, Boeing production personnel have been advised to make sure the bonding instruction on the installation drawings are followed.
Operator Action
Operators who experience movement of the temperature indicator when master caution is recalled or during any other operation may wish to measure the resistance between ground block GD506 and airplane structure. If the measured resistance is above 0.0035, Boeing recommends operators correct the condition.
yayoo
 
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