Introduction
Over Temperature alarms are quite annoying and they can appear even when the configured threshold limits cross 1 degree. Sometimes it is difficult to troubleshoot these over temperature issues because of their intermittent nature. In this article I will discuss about an intermittent "over temperature" issue and possible steps for diagnosis and resolution.
Problem
The issue was reported with below alarms
There were no hardware alarms seen on the box and all the modules appeared to be healthy.
Solution
The first step of troubleshooting will be to check if there is any hardware error. But in this case all parts were functioning normally.
So from that point, we have to start thinking about the fans since they are responsible to maintain the temperature of the modules.
Here a couple of points are worth mentioning in relation to the maintenance of temperature of the modules.
1. By default the fans are running at full speed irrespective of temperature. However there is a new feature called "Smart Fan Control" introduced in the RFGW1 GUI (System Page).
Enabling this option will control the FAN speed based on the measured temperatures.
Disabling this option will make the FAN run at full speed. (By default this option is set)
Therefore we should check this option which by default is set to disabled.
Example:
2. The temperature of the surrounding area should be checked where the device is kept. Ideally, it should be around 22 deg C, although the RFGW1 is specified to operate up to +50 deg C
3. We should also check the FAN orientation whether the air is flowing from front to back. Air is supposed to be sucked in the front and emitted out at rear. If the opposite situation happens i.e. if the air is coming out when we look at the FAN's from front, then the fans are working in the backward direction.
4. Check if there is dust and contaminations accumulated on the surface of the fans. Remove the front panel with 2 thumb screws. Once the front panel is opened, all 4 fans will be visible.
Example
If there is contamination observed then below steps should be followed.
a. Unplug one fan.
Remove the 2 fan screws and the fan.
Using a paint brush, tooth brush, or some other suitable brush you get clean thoroughly the dirt off the fan.
See if the honeycomb surface behind the fan appears dirty and if dirty, clean that area as well.
Re-install the fan and plug it back in.
Repeat for each of the remaining 3 fans.
b. Take a look at the rear of the unit and verify that the holes in the QAM card rear cover are not blocked. If the holes are dirty then using the same brush, clear any debris from the holes in the rear covers.
c. Following the above 2 points, login to the Web GUI and go to “Monitor” -> Device Information and check the temperature becomes cooler.
Example:
Also check the syslog’s and verifies the frequency of the “over temperature” alarms.
d. If the above steps work in reducing the temperature, then please schedule a maintenance activity to pull out all the modules (fans and rear modules) and perform a thorough cleaning.
If none of the steps help to get rid of the alarms and if the unit temperature is still hot even after cleaning then we should take opinion from Hardware Experts and replace the fans or entire unit as per their final decision.