will "EQUIPMENT COOLING OFF" cause PFD/ND to fail?

[eagle737]

here is another disagreement between MEL and QRH, i'm flying 737ng.
If you see an Equipment Cooling Supply or Exhaust OFF light on when flying , what will you get? you follow the QRH, it tells you that "No further action is necessary in flight if the equipment
cooling OFF light does not extinguish."
But if you check MEL, it tells you that the display equipments will get damaged(in 30min? --i can't remember the number clearly).so what will you get on earth?
and i guess the difference is caused by the different usage/purpose of QRH&MEL, just like the item "one pack inoperative"?

[LEM]

On the Classic it won't fail. You'll loose some colours, maybe.
Don't know about NG.

[alexban]

Section 2
MMEL Air Conditioning
REPAIR INTERVAL NUMBER INSTALLED
NUMBER REQUIRED FOR DISPATCH
ITEM REMARKS OR EXCEPTIONS
21-27 Electrical/Electronic
Equipment Cooling
Blowers
1) Non-EFIS (-100/-200/
-300/-400/-500)
C 2 1 Except for ER operations, one may be
inoperative.
2) EFIS
(-300/-400/-500)
a) Supply Fans C 2 1 Except for ER operations, one may be
inoperative.
b) Exhaust Fans C 2 1 Except for ER operations, one may be
inoperative.
3) CDS
(-600/-700/-800/-900)
B 4 3 (M) One fan may be inoperative provided:
a) All remaining fans are verified to operate
normally, and
b) Both low flow detectors are verified
operate normally.


and if you lose the fans during flight :
OPERATIONS NOTE
-100/-200/-300/-400/-500:
Verify that the operative fan is selected and the EQUIP COOLING OFF light is extinguished.
For EFIS equipped airplanes, if the EQUIP COOLING OFF light illuminates during flight (both supply fans or
both exhaust fans inoperative), continued flight beyond 90 minutes can result in loss of essential avionics.
-600/-700/-800/-900:
If the EQUIP COOLING SUPPLY OFF light illuminates during flight (both supply fans inoperative),
continued flight beyond 30 minutes can result in loss of the Captain’s Display Units and the lower center
Display Unit. If the EQUIP COOLING EXHAUST OFF light illuminates during flight (both exhaust fans
inoperative), continued flight beyond 30 minutes can result in loss of the First Officer’s Display Units and the
upper center Display Unit.

so ,you can change Displays using the selectors to the available ones.

[eagle737]

thanks
so i guess
#1, the possibility of all of 4 fans failing will be very very small, and if you are unluck someday, you can only refer to the ISFD.
#2, lose of some display units is a way to protect itself not to be damaged, is that right?

[alexban]

only 2 fans ,on the same duct must fail in order to lose some displays (for ex both supply fans or both exaust fans).Depending of what fans fail you'll lose specific displays on the NG.
Due to lack of cooling the displays will be damaged after some time.Initially you'll lose some indications e.g. WX Radar !
The display will fail completly after given time.