This thread concerns a 10 year old Ruud UAMB-060JAZ 5 ton A/C.
A few months ago, we noticed that during the day our A/C unit was not cooling very well. Found out that our indoor coil was freezing up and we needed to defrost before we could get cold air again but only for a short time. Paid to have a tech come out and he said our unit was almost 2 lbs low on freon(holds 6 lbs). He recharged the system and it has been working as new.
Yesterday, we returned home from a 3 day trip to find that our house was hot. We had left the thermostat at 78 degrees but saw the inside temperature was at 85 and the inside blower was blowing hot air. Went outside and saw/heard that the fan and compressor were not running.
Went back inside and turned A/C to off resulting in indoor blower to stop. Waited a bit and then turned the unit back on - same result no outside fan or compressor.
Took cover off outside unit and all appears normal with no bug infestation, or loose or broken wires. Checked and reset both the breaker and the high pressure reset button. Still nothing.
Manually pushed down on contacter and bam, the compressor and fan kicked on. Tried holding the contacter down for about 3 minutes while my son checked the outflow air and the hot air got slightly cooler but not cold.. so the system may be once again low of freon? During this 3 minute operation, the top of compressor got very hot as did the small copper tube running to the outside cooling radiator coil. The bigger copper tube running to the inside cooling coil never seemed to get very cold though it was much much cooler than the smaller tube. Is that normal or possibly another side of low freon?
Hoping the problem was the thermostat, I directly connected the AC control wires bypassing the thermostat. As before, inside blower comes on but not outside fan or compressor. So, according to what I have read online, my next step is to see if the contacter is getting the 25v signal to the contacter coil from my thermostat?
Here is where I need your help, please. I have a sperry SP-10a but my use of it so far was only to measure battery power, so not sure how to set it and ESPECIALLY how to measure the voltage at the input and output of the contacter?
For example, do I turn the inside thermostat to ON before I measure the voltage? Do I need to remove the incoming wire from the contacter to measure it or do I just put the pos probe on the incoming connection and the negative probe on the outgoing (opposite side of contacter)?
- Just found these instructions online... do they look right to you?
** on the thermostat. Leave the condenser's circuit breaker off.
Inspect the conatctor's bus bar. If the bus bar depresses, the contactor's coil works. If the bus bar remains in the open position, turn a multimeter to its VAC setting. Place a multimeter probe on each of the contactor coil's wire terminals. If the multimeter reads zero, troubleshoot the air-conditioning system's low-voltage circuit. If the multimeter reads 24 to 30 volts, turn off the thermostat and check the contactor's coil for continuity.
Remove the low-voltage wires from the contactor's relay coil wire terminals. Turn the multimeter to its resistance or continuity setting. Place a multimeter lead on each relay coil wire terminal. Check the multimeter's readout screen for continuity across the relay coil. If the multimeter reads zero, replace the contactor. If the multimeter reads continuity, reconnect the low-voltage wires to the contactor's relay coil wire terminals.*/*
Other thoughts include wondering if the unit got low on freon again(due to a leak somewhere) and it caused a failure or some sort of compressor protection to initiate which is still in effect? For example, I can see and push the high pressure reset button but have no idea where the low pressure reset might be?
As you can tell, I am a relative newbie but one who must learn since I am a currently unemployed broke newbie with 2 kids and no A/C in 95 degree Texas, so any and all help is very much appreciated.
Thank you very much for your help!