My AC will turn on but will not blow out cold. I'm rebuilding the whole system, ductwork and all.

I've shorted the thermostat's red (power), yellow (a/c compressor), and green (fan) wires together. The handler and compressor are both running. However, the system blows out room-temperature air.

What could be the issue? I haven't run the system for over a year, so it could have gone bad at any time really. Only thing I can think of, is that possibly the refrigerant is low, but I have no idea how to check it. The insulated refrigerant line doesn't seem to be getting cold. The compressor and interior of the handler are mostly clean - a little dirt/dust, but I doubt that it'd totally starve the system.

Is there a way to narrow down my search some more?

  • Are you sure the compressor's running? Maybe just the condenser fan above the compressor is. – JACK May 31 at 22:19
  • It sounded like it was, giving a distinct "brrbrrbrrbrr" noise, and felt like it was vibrating. But maybe it was just the condensor fan making all the noise and motion. Is there a way to isolate and check the compressor? – Tyler M May 31 at 22:25
  • Do you have an AMP meter? – JACK May 31 at 22:32
  • Yes, I also have most other electric/hvac tools – Tyler M Jun 1 at 2:36
  • You have probably already checked capacitors but if you haven't that's one of the more common failure points with whole house ac. – HoneyDo Jun 1 at 3:11

Here is the thing, if you don't know what you're doing with respect to an HVAC system, then please call a licensed professional. There is the potential for injury to yourself and others if you do the wrong thing. It's also illegal to handle many refrigerants without a license in many locations.

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  • I've taken the literal entire system apart so I know it inside and out. I've seen inside handler, read way too much documentation on my system, re-ran all the electric, gutted and re-run all the duts, set up the handler myself... maybe famous last words, but I'm pretty sure I can handle it. I'm just looking to diagnose - if I find out i need a refrigerant refill, I don't mind calling a guy to come refill it. But I'd like to save myself the money and diagnose if i can. – Tyler M May 31 at 22:23
  • There is no dipstick to check the refrigerant level. You attach a set of HVAC gauges to the high and low-side ports, read the pressures, calibrate the readings according to the temperature, and validate your measurements against what they should be. – jwh20 Jun 1 at 10:46
  • I'm pretty sure they don't make refrigerant checking easy because it's suppose to be done by a licensed professional and the stuff can kill you. – Nelson Jul 1 at 2:57

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