Any A/C diagnostic geniuses Out there?
 

Any Jr. A/C diagnostic sleuths out there?

Here's the problem. Happens intermittently (last time was this morning at 2AM).

A/C stops cooling yet the compressor fan outside continues to run as if all is OK.

Here's what's been done so far:

New Capacitor
New Contactor
New Fan motor
Condensate drain is clear and drain switch tests OK.
Refrigerant is fine

Problem is, every time the repair guy comes out it is working again. It stops cooling usually for a couple hours at random times. Sometimes it can go for 2 weeks without issue then it happens again.

It's an 8+yr old Carrier unit that was part of the original construction (I'm 2nd owner). When it is working it cools perfectly so it isn't a refrigerant issue.

It could be a stuck or clogged thermostatic expansion valve. I had a similar problem with a new Carrier system installed several years ago in Virginia. This was the result of a Carrier defect in the compressor which cause circulating oil to clog the valve orifice. Although this is just speculation.

If it's a carrier heat pump the defrost circuit board may have a fault. I only know this from previous experience going way back.

You might want to ask your AC company to escalate the problem to one of the Carrier factory support techs since they appear to be having trouble diagnosing the issue. This may only be possible if they are a Carrier Factory Authorized Dealer. If they aren't, you may want to consider going with a different AC company. When dealing with techs, I believe you should refrain from telling them what you think the problem might be and instead focus on describing the symptoms only, as accurately as possible. For example, is the system running normally and then the compressor cuts out or does the compressor fail to start when the thermostat calls for AC?

check the following : 1) circuitboard 2) thermostat 3) control wires- loose connections--or a rodent chewing on a control wire-- all mechanical components have been covered

My bet is the start capacitor, even though it has already been changed. We had an issue last summer with the a/c working intermittently (Carrier unit), sometimes it was ok for a few hours, or days, then it wouldn't work, then back to ok. The unit was still under warranty, and the tech from Munns had it fixed within 20 minutes. He told me he replaces at least 20 start capacitors almost every week.

I have an associate-with the same problem--it was the main circuit board in the house unit--they normally croak in 6 years

Is the A-coil freezing up?? If it is, not only will it not be cooling well, but you will notice almost no air flowing from your vents.

Thanks everyone. Now I have something to tell him.

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Nope. Damn It just happened again. Noticed temp up to 81 while set at 76. Checked outside and inside. No frozen coil inside, fan still spinning outside but coolant pipe is warm. Weird part it just started working again about 45 minutes later.



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more advice=--circuit board in the condensing unit & if its a heat pump, might be the reversing valve coil, not holding the reversing valve open--more info from associate who is in the business

How many service calls have you had? The guy should have been able to spot the problem. Normally they have the tools and experience to know what the source is likely to be. I would call the company he works for and try to get someone who knows the system. Your in an age of unit when things start to go wrong. For a while, it will still be cheaper to fix than buy new, but you have to have a solid repair man or the service calls will eat you alive.

Well ...... it's under a home warranty plan so I only pay once. Problem is, after the initial call they aren't happy to return, but they do. Their gripe is (and probably rightfully so) that it is always working when they get here so, says he, they can't "see what's wrong." I'm hoping (legitimately) to drive them so crazy they will just eventually replace the unit. Fortunately for me it works 85% of the time and just randomly shuts down for an hour or 3 whenever it wants. The tech is basically just a "parts replacer" and is overloaded with calls. The right thing would be to have a Carrier Tech sent out but I don't want to pay for that on a system that is pretty much at the end of it's life. So far all I have invested is $100 and some of my free time. Will see how they respond to service call #3 when I call in on Monday. Not sure how much of a real complaint I have if it is always working when they get here.

In my opinion, home warranties are a ripoff. I seriously doubt that they will ever replace the unit.

Not sure about ripoff but definitely a PITA however I have no doubt I will get my money's worth out of it. :evil6: I just plan on keeping it for 1 year.