If your NexStar hand control starts to act strangely or won't run through the alignment procedure correctly, a potential solution is to use the "Factory Setting" option on the "Utilities" to reset the hand control to its default settings. This has even been reported to work on new scopes and replacement hand controls received directly from Celestron. Do note that this will erase stored settings such as Filter Limits and Slew Limits.
In the event the NexStar version 4, NexStar+ or StarSense hand control will not start up normally and you cannot access the menu, there is another option. Power down the scope, hold down the 0 button on the hand control keypad and power up the scope. This also performs a factory reset of the hand control which may allow things to proceed normally again.
For the NexStar 60/76/80/102/114/4/130 GT scopes, reselecting the model via the menu resets the hand control to factory settings (if you have the N130GT, you should select NexStar 114 as the model). If you have or suspect you have the old version of the GT hand control (or the Tasco StarGuide hand control), be sure to read the model selection information here.
With the first version 4 upgradeable hand controls manufactured, the display might come up blank when you power up, a problem much more prevalent in cold weather. The fix on those occasions is to turn off the power, wait a couple of seconds and turn on the power again.
Another common cause of misbehavior is low power. See this article for power source suggestions.
Another potential problem is on the very old hand controls with socketed circuit chips. If the chips are not seated well, all manner of odd behavior can occur. Open the hand control (there are six small screws on the back of the hand control) and push the two medium-sized circuit chips firmly into their sockets. Note that newer hand controls do not have socketed chips and this does not apply. Prior to touching the electronics, it is best to touch a piece of grounded equipment such as the metal frame of a computer or washing machine. When reassembling the hand control, be careful not to tighten the screws too much or you may strip the plastic case.
If the backlight on the display lights up but no characters appear (or they are very faint), open the hand control and insure the flat cable leading from the LCD panel to the circuit board is firmly seated in its connector.
If the hand control does not seem to power up, the problem might be the connector that the hand control plugs in to. Try connecting the hand control to one of the AUX jacks (for mounts with an AUX jack), rather than the normal hand control jack. Also, the pins on the jack or the plug can accumulate slight amounts of corrosion that can interrupt the low voltage signals. These can be easily cleaned with contact cleaner available at electronics parts stores. Do not over do it, you do not want excess cleaner to short out the electrical connections. Be sure the power is off and use a cotton swab dampened with contact cleaner to rub any contaminants from the connectors.
Another potential problem area is that the plastic RJ-12 connector (phone-type connector) on the end of the coiled cable might need to be re-crimped or replaced. Or, occasionally the connection of the coiled cable inside the hand control has worked loose. This can be fixed by carefully removing the back of the hand control (6 screws hold it on) and reseating the connector.