This is an 18 year old Lennox 5 ton 2 speed central AC unit. Over the years it has not been used much as I am not an AC guy. The unit is in good shape. I know a little about basic AC so that makes it a little easier. Out of the blue the condenser unit, fan and compressor will not start. I checked the low side pressures with my gauges and they are good, it should start. I checked further and found the large contact relays not pulling in. I held in the relays manually and the unit started fine.

My question is which one of these relays may be bad or is it another part that controls these relays that is bad. Is there another component that goes with these relays that can also be bad. I think it may be a control issue but not the thermostat as I can hear the small plastic relay clicking as the thermostat is turned on and off. I don't have a drawing of this particular AC Unit.

Can someone suggest a good place to buy AC parts over the internet.

The Model number is HS 14-651V-3P

Thanks

Check your coil on the contactor. I bet its bad.

WOW, Well in a later post you have 15 years experience in hvac, what a joke!!

Now you only know a "little of the basics". In an earlier post you've had 15 yrs. In the field. With 15 yrs, I would think you could do a little troubleshooting.Talk about doing you homework. I think you are the "dumb" one. This is a very good forum and not one to put people down on.