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I have a Carrier heat pump/air handler system (looks pretty old) with a honeywell T-stat (looks pretty new) and I am not getting cool air. Heat worked all winter, but I have used it in at least a month. The fan (inside unit, air handler) seems to work fine. The outside unit (compressor and fan) do not come on. I just replaced the filter and the T-stat batteries, and I tried resetting the breakers for the air handler/outdoor unit.

I opened the outdoor unit, and it comes alive when I push the contactor in. If I hold it in for ~10 seconds it will click and stay on after I let go. It sounds like both the compressor and fan are running at this point, but I still get no cooling. Sadly I don't own a multimeter yet. Is there anything else I can check myself, or is it time to call for service?

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up vote 4 down vote accepted

If both your central air handling fan and outdoor compressor are running and your not seeing any sort of cooling after a 10-20 minutes than I'd venture a guess and say it's time to call an AC repair service.

I'm curious what you are pushing in that makes the compressor turn on? Are you somehow bridging the main capacitor? Capacitors tend to be a common point of failure on AC units and can actually be changed fairly easily. Here is a pretty good article detailing the steps to do so.

To be honest though I'd guess that the bigger problem is the fact that you can get it running and it still isn't putting out cold air. The whole situation sounds like it's low on coolant (have you had it filled in the last few years?). AC's usually have a low coolant pressure switch that will keep the unit from running to prevent damage to the compressor when there isn't enough pressure.

Call an AC service out, many will diagnose your problem free of charge and be able to give you a much better idea of your problem. Be warned though, if your system is old and uses R-22 prices have shot up in the last year.

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Thanks for the reply. My multimeter is coming in the mail today, so I will probably poke around with that this weekend, and end up calling for service on Monday. Obviously low coolant is beyond my capabilities, and I haven't had it filled since moving in. The capacitor looks OK (no obvious bulging/leaking) but I obviously don't want to touch it and I don't have a discharger. To make it run, I am pushing in the contactor, which is basically a relay. Signal from the T-stat should cause it to "pull in" connecting high voltage for the compressor and fan. –  aganders3 Jun 22 '12 at 14:51
    
I'm curious to know what the problem is if you find it, be sure to update when you do! –  Eric Anderson Jun 25 '12 at 22:15
    
I had someone come out today and it was as you suspected: totally empty of Freon. Sadly my system is old and used R-22, so it wasn't cheap. There were no obvious leaks, so I'm just hoping it will hold now. I think a new system is in my not-too-distant future. –  aganders3 Jun 26 '12 at 20:16
    
Sorry to hear, that doesn't sound like a fun repair bill to be stuck with at all. It's concerning that your system was that low on R-22 but yet they didn't find any leaks. I've heard of Freon theft and kids supposedly getting high on the stuff (ridiculous idea btw). You might check your local police blotter to see if others have reported anything like that and consider a locking cap in the future to prevent anything of the sort (as goofy as that sounds). –  Eric Anderson Jun 29 '12 at 21:22
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