Air Conditioning - Please help with lennox System

Hi, I have a roof top mounted lennox ac,heating home unit that is all electric, It is about 13 years old and the model # ECHI6R-7-IP. The problem is the unit will not produce heat or AC when you turn it on. The fan works normal on auto or manual but the unit does not kick on. I checked the circuit brakers and the fuses on the unit and they are fine. When you turn the unit on you can hear a click from one of the clear plastic relay boxes. After looking at the unit for a while I noticed some contact points that were not touching so I manually pushed them together and the unit comes on and performs great hot or cold as long as i hold those points together. It looks lke a magnetic point switch with some corrosian on the contact surfaces. The part that has the points has two numbers #3100-15Q108 and 656901. This part also says coil 24Vac, 50/60 HZ, 4391 and gives Contact Rating per pole values-VAC, FLA,LRA, Res. Is the problem this contact switch or could it be another switch that ignites these points? please help. Larry

It could be either the contactor (that part with the 24 volt coil) is defective OR you could have a thermostat problem OR a wiring problem between the thermostat and the AC unit. If you have a multimeter you can try measuring across the contactor coil to see if you have 24 volts there or you can try using the ohms function to see if the coil may be open.

could be a low or high pressure switch too......

be sure there is 24 volts coming into the unit on the tstat wire, then follow it and see where you lose it. if it is present at the contactor (what you pushed in) it may very well be bad