My outside heating/air unit will not turn on . I opened the panel and if I push this little spring loaded thing it contacts with a small circular object and the unit kicks on, when I release it turns off. It's a brand new unit, about 5 or 6 months old. Can I fix the problem myself. Repair guy can't get here for a couple of days and it's going to be cold this weekend.

Did you check for 24 volts at the contactor low voltage terminals? If the 24 volt signal is not getting to the contactor it will not pull in so just pushing it in manually does not prove it is defective. In other words the contactor needs a low 24 volt signal to work. When everything is turned on to operate like the thermostat does the 24 volt signal exist?

I have n't checked for the voltage, if it is the voltage, what's the cause?

If you are missing the low voltage to the outside unit there could be a few different parts involved and to find them you will have to post for both the inside and outside unit the following

Brand of units?
EXACT Model number of both inside and outside units.

Do not post the requested info until you find out exactly weather or not you have the 24 volts.

Outside unit is a Payne model # PA13NR036-H Inside is Payneodel # PF1 MNC036

Do not post the requested info until you find out exactly weather or not you have the 24 volts.

Safety devices can also prevent the contactor from pulling in, so can a LOT of other problems.