Temperature related failure

[Holgi 1]

Hello!Every tenth flight or so I get a master caution with that yellow zone temp indication on the OVH (see pic)I have no idea what is wrong because all temperatures are in normal ranges. Any idea what I can do?

[davierosoft 13]

If the picture is taken just after the failure it is an issue. The supply duct temp. is too low to arm the zone temp light.It was a bug pre SP1 if I remember correctly.

[flyerboy 114]

Got it yesterdayEither lower the temp, or press the "trip reset" directly under the isolation valve switch.

[davierosoft 13]

I never had the light on on my plane, so just curious at what outside temp? What temp setting and what supply duct temperature did you have the light on?

[Holgi 1]

I think it has nothing to do with outside temp. I think it depends on the setting of temperature on board. I think the temperature was to low when I got the message I was wondering why the light is still on although the temperature is already in a normal range.

[ZachLW 37]

2.24 of the QRH (Quick Reference Manual) PDF. Use Ctrl-F to search for "Zone". That PDF is located along with the rest of your manuals in the Windows start menu.

[Spin737 102]

The duct overtemped or you have a controller fault. Follow the QRH as previously suggest. If you want to know more about why the light went off, dig in to the FCOM.It's a little confusing, so pay attention to the notes. If the light comes on only when you hit recall, it's a controller issue.

[davierosoft 13]

I think it has nothing to do with outside temp. I think it depends on the setting of temperature on board. I think the temperature was to low when I got the message I was wondering why the light is still on although the temperature is already in a normal range.

Outside temperature (so initial cabin temp.) has a lot of influence on how the cabin will be cooled, if it will cool fast then the trim air will command hot air to give a warm command, this can heat the duct untill zone temp come on. Normally is more a problem on the sorter versions (6-700) wich uses mix valves.However in your screenshot the duct temperature is normal so it is more related to the pre-sp1 issue.

The duct overtemped or you have a controller fault. Follow the QRH as previously suggest. If you want to know more about why the light went off, dig in to the FCOM.It's a little confusing, so pay attention to the notes. If the light comes on only when you hit recall, it's a controller issue.

The controllers have redundant channels, if one fail it can be seen only at recall, if both channels fail, master caution will come on. Assuming that controller channels are both functioning (check failures) it is a temperature problem. Tis will be confirmed if pushing trip reset when temp. are stable will remove the light.In case of controller failure the light cannot be extinguished by the reset.

[Spin737 102]

The controllers have redundant channels, if one fail it can be seen only at recall, if both channels fail, master caution will come on. Assuming that controller channels are both functioning (check failures) it is a temperature problem. Tis will be confirmed if pushing trip reset when temp. are stable will remove the light.In case of controller failure the light cannot be extinguished by the reset.

I know this well - I had this controller fault last week on one of our -400s and I had it this summer on an -800.

[Jeffrey L. Whitaker 0]

Holger,Andrea is correct (see post #4 of this thread). Please ensure you have correclty installed the PMDG NGX corrextly up to the current build (1b). In the interim simply adjust the AUTO temperature selector a few degrees in favor of the cooler © side and reset the warning light. JW

[Holgi 1]

Holger,Andrea is correct (see post #4 of this thread). Please ensure you have correclty installed the PMDG NGX corrextly up to the current build (1b). In the interim simply adjust the AUTO temperature selector a few degrees in favor of the cooler © side and reset the warning light.JW

Thank you all!This is exactly what I have done. Nevertheless it seems that I have to do a deeper look into the manual according this issue.

[HiFly 16]

You may have already done this, Holger, but my suggestion as a first step is to reset all temp controls back to AUTO and then press reset button. If reset fails to extinguish the light, check the supply duct temps. My experience, however, has been that even after a discrepency has been corrected the light has continued to remain on until I pressed the "reset".

[Spin737 102]

reset all temp controls back to AUTO and then press reset button

This is a common misconception and maybe you know, but in the -800 and -900 there is only AUTO and OFF. There is no MANUAL mode. In the pic, the CONT CAB is set to about 25C.A common cause of this problem in RL is starting up a cold plane. The controller sees that the zone is way below the desired temp and pumps in enough heat to trip the overtemp and Zone Temp light.In this case, that type of error doesn't make much sense since you're in flight. It could be a controller fault or a bug.

[davierosoft 13]

And the OFF is again an automatic control... Aircraft will change its logic to fixed temperatures.

[Spin737 102]

And the OFF is again an automatic control... Aircraft will change its logic to fixed temperatures.

Good point.