On outside compressor for whole house AC: Critters ate wires. Have Blk & Red power in from breaker. 24vac switched from thermostat. 1 contactor with 24vac coil(original). 1 Capacitor w/ 3 terms labeled: C, fan, herm. compressor w/ 3 wires: #10 yel & blk, #14 red. fan w/ 3 # 18 wires: Blk, Orn, Blu. I need wiring. Here is what I think: All blacks connect together. Red power wire connects to contactor in. Fan orn & Compressor Yel go to contactor out. Capacitor is the problem. "C" marked terminal goes to contactor out. "fan" marked term goes to fan blue. "Herm" marked term goes to compressor Red. Is this correct? and what ther heck doas "HERM" saand for?

It sounds like that unit is connected to a "power saving load controller" device from the power company. The power company can turn your unit on & off with a radio signal. If you manually activated contactor and unit ran. I would bet that the power company's device or the wiring connecting it is where the problem lies. Call the power company and have them check their device. If they tell you that the device has been tested remotely and is working fine. Explain to them that you can activate your unit manually and it works fine. They should not charge you to come out. Those "load controller devices" have a pretty good longevity record.

If you held the contactors at the condensor in and the outdoor fan and compressor started, you have a control circuitry problem. The thermostat is more than likely wired incorrectly. The red wire at the t-stat is the 24VAC hot. If you touch it to the green wire the indoor fan should start. If you touch it to the wire that is going to the coil on the contactor you pushed in (color unknown as I am not there) it should fire the compressor and outdoor fan. Thermostats can be very tricky sometimes. Based on what you have written it is definitely a control voltage problem. If you do not have 24VAC you need to check the input power on the transformer and make sure you are getting 24VAC output.

Whatever you do....do not take the red wire on the t stat and arbitrarily connect it to any other wires. One of those wires is the neutral side of the transformer and if you touch the hot red to it you will have a direct short and will need a new transformer.

If this has helped you please give me a rating I can be proud of. Thank you and best of luck.

At the thermostat you have several colored wires. Touch the green and red wire together and see if the indoor fan comes on. If you know what wire goes to the coil on your AC contactor touch the red wire to that wire. If it starts the outdoor fan and your compressor the thermostat is not wired correctly. All you are doing by my suggestion is bypassing the thermostat to eliminate it as the possible problem.

The outdoor AC contactor coil wire is usually yellow or blue, but you must make sure not to short the red wire to the other side of your transformer as that will cause you to have to buy a new transformer. Your unit wire diagram should show the wire to the AC contactor coil. You need to determine which wire feeds the AC coil which closes the contactor to the compressor and outdoor fan motor.

If this helps please rate me at fixya.com

Remove the thermostat face and place a jumper between R and Y. The outside unit should come on. If it doesn't, check for 24vac between R and C or R and Y. If you don't have it then you need to check the transformer. Check for 24vac on the transformer secondary and 120vac on the transformer primary. If you don't have power on the primary, check for a blown fuse or tripped breaker. If you do have power on the primary but nothing on the secondary, you need a new transformer. If the unit does come then the thermostat is the problem.
If the transformer is good and the unit doesn't start when you install the jumper then you have a problem in the outside unit. It could be the contactor coil which you can check with an ohmmeter. It could also be a low or high pressure switch or and overload all of which you can also check with an ohmmeter. Let me know what you find.

Turn the breaker on and remove the cover from the A/C and check for proper voltage coming into the unit. If you don't have it the circuit breaker may be bad. If you do have it, set the thermstat to make the A/C try to come on and check the contactor to see if it is pulled in. If it is pulled in, check for voltage on the load side of the contactor. Also check the condition of the contacts, make sure they aren't really burnt or pitted. If it isn't pulled in, check the output of the low voltage transformer. It should be 24vac. If you don't have it verify you have power on the primary side of the transformer. If you have power on the primary and none on the secondary the transformer is bad. If you have 24vac, go to the thermostat and install a jumper between R and Y. If the contactor pulls in with the jumper installed then the thermostat is bad. If the contactor doesn't pull in with the jumper installed, check for 24vac on the contactor coil. Notice you will have line voltage on L1/L2 and low voltage on the coil so use caution. If you have 24vac and a jumper installed and the contactor still isn't pulled in then the contactor is probably bad. You can also check for low or high pressure switches. If the contactor and thermostat is good then check your capacitor. Let me know what you find and I can give you some more suggestions.

First check the circuit breaker or fuses. Remove the cover on the outside unit that covers the contactor, circuit board, and capacitor. Check for voltage on the line side of the contactor. Set the thermostat to make the air come on then check the contactor to see if it is pulled in (contacts closed). If it isn't pulled in then check for 24 vac on the contactor coil. If the contactor is pulled in check for voltage on the load side of the contactor. If you have it there then check the capacitor(s). Some units have 1 that runs the fan and compressor and some units have 2 ( 1 for the fan and 1 for the compressor). If you don't have 24vac at the contactor you can install a jumper at the thermostat between R and G if it is just an air conditioner or R and Y if it is a heat pump and see if the thermostat is bad.

Check for power at the contactor. If no power there, check the circuit breaker, disconnect, or fuses. If there is power at the contactor, set the thermostat to call for a/c then check the contactor to see if it is pulled in. If it isn't check for 24vac at the contactor. If no 24vac then go to the thermostat and place a jumper between R and Y; that should make the contactor pull in if everything is good. If it does pull in when you install the jumper the problem is your thermostat. Let me know what you find.

You probably need a hard-start kit. A hard-start kit connects to the run capacitor and provides a starting boost for your compressor. If you install a hard-start kit, monitor your a/c for a while because it is possible that the bearings in the compressor are going bad.

Control wires come from the thermostat to power the contactor coil. At the thermostat the red wire must power (switch) the yellow wire to make the contactor pull in to run the outside unit, Check power with a ac volt meter between the red wire and the yellow wire, with the heat/cool switch turned to off. If you do not have 24 volts ac, your wire may have an open from the thermostat to the outside unit, your transformer may be bad and not supplying power, or your contactor coil may be open

open the service panel to check for control voltage of 24volts when tstat calling, The contactor should be pulled in, if contactor is down,and contacts appear to be clean, and the unit is still not running, it is a bad compressor. to test this unplug the black wire from the compressoror at contactor,w/ power off! Turn on power if fan works normally it's a bad compressor. However if you see a swollen split cap(5 wires to a soup can looking w/ the terminal C,F,and Comp), switch it first and start at square one.
You also need to consider the high pressure switch if its cycling on off on off.