Ask Me Help Desk - Outside unit won't run

Hi everyone,

I just joined the forum and glad to see folks willing to help out. I installed a new thermostat on my aircondition up at our camp. It had an old Honeywell tstat and I replaced it with a White Rogers digital. After installing it, it work fine. Heating and a/c unit came on, no problem. Well, we got there this past weekend and the freon had just about leaked out. I wanted to charge it up and check for a leak so I put freon in, without it running. When I got some in I turned on the t-stat and the unit would not come on. Not even the fan. I am getting voltage from the tstat because the relay connects but nothing comes on. I am getting voltage from the relay to the capacitor and from the capacitor to the fan and compressor. The relay sounds like it is buzzing(very low sounding buzz) when the tstat is on, but when I just close the relay from outside (tstat off), it does not buzz. It's not the compresser or fan buzzing, just the relay. I even put the old tstat back on and same result. For the life of me, I can seem to figure out what is wrong. I thought the outside fan should at least come on, but nothing. Please, any help will be appreciated.

Thanks,

Todd

Your low pressure cut off is probably holding the unit off from the low pressure in the system. If the unit was out of freon/refrigerant you first need to find the leak. Then you need to vacuum the system down for a few hours. Then you need to recharge the unit for proper operation. This is best left to a professional and if the unit was out of gas for a few days a drier should be put into the liquid like to prevent any moisture problems.

A test you can do to see if the low pressure switch is holding the compressor off.
Find the contactor/starter for the compressor and fan. Then use a screw driver to push the contactor down manually. If the compressor starts and the fan takes off it is a low voltage circuit problem and the low pressure switch is causing the unit not to run as I stated before. You could also jump the two wires to the low pressure switch to make a temporary connection for the test.

NOTE be very careful when working with line voltage/220 volt circuits.In other words do not allow the screw driver to slip on the contacts. Also this is only for test purposes. Do not let the unit run for more that 2 to 5 seconds. You will know if the compressor or fan kicks on right away.

Good luck with your testing.

Quote:

Originally Posted by toshgaal

Hi everyone,

I just joined the forum and glad to see folks willing to help out. I installed a new thermostat on my aircondition up at our camp. It had an old Honeywell tstat and I replaced it with a White Rogers digital. After installing it, it work fine. Heating and a/c unit came on, no problem. Well, we got there this past weekend and the freon had just about leaked out. I wanted to charge it up and check for a leak so I put freon in, without it running. When I got some in I turned on the t-stat and the unit would not come on. Not even the fan. I am getting voltage from the tstat because the relay connects but nothing comes on. I am getting voltage from the relay to the capacitor and from the capacitor to the fan and compressor. The relay sounds like it is buzzing(very low sounding buzz) when the tstat is on, but when I just close the relay from outside (tstat off), it does not buzz. It's not the compresser or fan buzzing, just the relay. I even put the old tstat back on and same result. For the life of me, I can seem to figure out what is wrong. I thought the outside fan should at least come on, but nothing. Please, any help will be appreciated.

Thanks,

Todd

Thanks for the fast reply. I did push the contact manually and still nothing happens. There is a wire coming from the relay to the capacitor and when relay is pushed, I get 120v to cap. I am also getting voltage from all outlets of the capacitor. That is what is puzzling me.

Check for 220 voltage on your outside disconnect. Many of these are fused in such a way so the fuses are not visible until you pull out the disconnect part. You can also check across the line side of the compressor/fan contactor to see if you have 220 volts there. From what you said it might be that you are only getting 110 volts at the unit and you need both legs of 110 to have 220 so the unit will run. Now its time to get to work and check to make sure you have 220 volts.Post back with your findings.

Quote:

Originally Posted by toshgaal

Hi everyone,

I just joined the forum and glad to see folks willing to help out. I installed a new thermostat on my aircondition up at our camp. It had an old Honeywell tstat and I replaced it with a White Rogers digital. After installing it, it work fine. Heating and a/c unit came on, no problem. Well, we got there this past weekend and the freon had just about leaked out. I wanted to charge it up and check for a leak so I put freon in, without it running. When I got some in I turned on the t-stat and the unit would not come on. Not even the fan. I am getting voltage from the tstat because the relay connects but nothing comes on. I am getting voltage from the relay to the capacitor and from the capacitor to the fan and compressor. The relay sounds like it is buzzing(very low sounding buzz) when the tstat is on, but when I just close the relay from outside (tstat off), it does not buzz. It's not the compresser or fan buzzing, just the relay. I even put the old tstat back on and same result. For the life of me, I can seem to figure out what is wrong. I thought the outside fan should at least come on, but nothing. Please, any help will be appreciated.

Thanks,

Todd

Now that you mention it, seems like I remember only having 110 volt on one side of the relay. The other side had nothing. I will also check the circuit breaker. It is turned on and off every time someone goes up there and those breakers are nearly 30 years old. Thank you so much for your help. I will let you know next time we go up if it fixed the problem. Have a great day and thanks again.

Todd

No problem. All of us here like to help people with problems if we can.