Posted: 11/25/2012 12:23:50 PM EDT
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Go home today from vacation. Found that our downstairs unit was not working. The fan was not blowing, and the thermostat says "Inside Temp 60, Set @ 70, AUX Heat".
Went out side, removed the fuse thing from the side of the house. Fan didn't start. Opened the cover to the blower outside unit. I have had to replace the capacitor before. here is a picture of the current capacitor. Does it look blown? It's not puffy, but there is some yellowish liquid on the top. 
Anyone have any suggestions? |
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Do a mF reading on it and compare it to the spec on the side. +-6% of the spec means it's good. If it's leaking, it's probably bad.
If everything else works except for the blower, you can always do a call for heat and manually give the blower wheel a spin to see if it starts to spool up or you can check for 120 voltage out of the board going to the blower motor on a call for heat/cool. Also, it's very helpful if you give a bit of into like fuel type, make, type of system and where the process stops. [or if it's completely dead] If the blower is bad, you may have a tripped roll out switch or limit and that would stop the process before it ever got to the blower on part. |
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Quoted:
Do a mF reading on it and compare it to the spec on the side. +-6% of the spec means it's good. If it's leaking, it's probably bad. If everything else works except for the blower, you can always do a call for heat and manually give the blower wheel a spin to see if it starts to spool up or you can check for 120 voltage out of the board going to the blower motor on a call for heat/cool. Also, it's very helpful if you give a bit of into like fuel type, make, type of system and where the process stops. [or if it's completely dead] If the blower is bad, you may have a tripped roll out switch or limit and that would stop the process before it ever got to the blower on part. Going to have to find a friend with a mF option on their multi.. mine doesn't have it for some reason. |
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The capacitor is the starter and possibly the device that keeps the compressor running. There should be a large controller relay that can CAREFULLY be manually pushed in with an insulated item like a dowel. If the compressor starts, the capacitor is ok. The outside fan should also start along with the compressor.
The thermostat may trigger a smaller relay that fires up the controller relay or it may switch the controller directly. I can't tell you what color wires to test because not all installations are standardized but basically all the thermostat does is close a contact that completes the circuit to fire the coil of the controller relay. The thermostat control circuit works off 24 volts A.C. and if the thermostat is not working, the outside unit will not come on. You may find a diagram that will show you what wires to short to simulate the thermostat while you are in the outside unit. Generally the inside blower is either thermostatically or timed controlled and should come on after the outside unit is on for a while. |
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so much of that last statement is wrong. not all controls work on 24 volts ac, more and more work on dc voltage or communication systems. normally stat calls fan and compressor contactor for cooling or heat pump compressor contactor and cu fan starts with compressor or in colder climates by head pressure |
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Quoted:
so much of that last statement is wrong. not all controls work on 24 volts ac, more and more work on dc voltage or communication systems. normally stat calls fan and compressor contactor for cooling or heat pump compressor contactor and cu fan starts with compressor or in colder climates by head pressure I know most stats rectifiesAC off a transformer to DC for their internal workings but I left that out for simpliciy. The units I have seen start the compressor and outside fan when the control relay is depressed. It is generally a good way to begin troubleshooting the system. |