Testing ideas for AC that cools intermittently

[dfphoto]

Hi my friend lives in a high rise condo and her AC is acting oddly. If you set the thermostat at 73 the unit will go to about 76 (79 normal without AC) outside about 85 on average (this is West Los Angeles). Anyway, had an AC guy swing by all he did was check the gauges and left a bill for 125.00 says all is good.

 

I replaced the batteries in the thermostat and that seemed to work a while then the AC went back up to 76. The next day we tried 65 as the setting and the AC went down to 70 but that lasted one day the  next day it wouldn't go below 76.

 

Wondering if you guys can offer me some testing ideas to see if I can at leaset pinpoint what could be wrong. I read the compressor could be worn out as the unit is probably the original from 1983. Also read there might be belts in the compressor fan assembly but haven't seen them yet.

 

Appreciate your help in advance. Dave

[weswayne]

I am not an a/c guy but did anyone check the air filter?

[johntech]

Did you have the unit running prior to the tech showing up? If you turn it on and it cools and had it off when the tech showed up then it would have been cooling during his testing and he would not have been able to find a problem. You need to have the ac in a failed state before he comes. If it was blowing warm air when he was there and he told you it was working then you need to call a different tech.

[johntech]

A lot of people think they are doing good by turning ac and refrigerators off when they are broken, but it actually takes away a lot of evidence we need to properly troubleshoot Properly.

[dfphoto]

Hi group, well in West LA you can't have a problem and call and have someone pop in. Usually a week in advance and it's a bit hard to pinpoint when it will do this. However, I've never seen the temp go below 73 before (but maybe it was never set that low).  Anyway, the filter is replaced regularly, and one test the guy did was to remove the filter and feel the fins but I did that and one time it was icy cold almost wet on the top and warmer on the lower fins. Then a bit later it was basically warm/cool about 73 ish  and then later it was cooler moist like. Never the same, so it's a bit odd, I don't understand this guy only checking gauges though. I had my AC checked out and the guy took the panel off to look and then up on the roof. My situation ended up being freon but not this guy. Again this is a high rise and it's a big deal to get a contractor in the building the HOA checks all the paperwork, insurance Workers Comp etc....

 

Noticed it pisses off a lot of contractors.... Anyway, is there anything I can check just to see if I can get some ideas?

[ACtechGUY]

Does the inside fan shut off  if you are still above setpoint ? or does it keep running but no cool air is coming out?   

 

Digital thermostats can malfunction in unusual ways causing the problems you are seeing. To test, you can remove the thermostat and connect the R Y and G  wires all together. This will bring on fan and cooling,  effectively bypassing  the thermostat.   the inside fan will run along with the outside unit 100 % of the time . it will not shut off.   If you notice it starting  not blowing cold air after a while , you have eliminated the thermostat as a possible cause. 

 

Alternatively you can go and buy a new thermostat and install it . set it at 65 and see if it keeps cooling without stopping.  

 

If it is not the thermostat , that leaves a strong possibly of a problem at the condenser outside , like a failing fan motor, capacitor(s), or dirty condenser coil to name a few.  

[Spannerwrench]

I know if it was me and I had a 30 year old AC I wouldn't call someone to fix it.  I would be calling them to replace it.  But AC Tech is right, a thermostat could cause a lot of the problems you're describing.