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Old 06-07-2012, 12:05 PM   #1
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correct pocedures for diagnosis or troubleshooting

I have one unit residental about 13 yrs old. I think I remember it being serviced maybe 3x in those years. The A/C isn't blowing cool air. The outside condenser unit has stopped running. I go to the t-stat and it doesn't turn off. I go up to the attic to turn it off with the switch. The service tech comes and replaced the contactor and handed me the old one which didn't look burnt or damaged to me. He also took out the bypass switch since our circuit breaker is just 4 ft away, he said it's not required and it looked damaged. It didn't look it to me but I'm going along with this. The outside unit finally kicks on. He checked the freon and said it was o.k. 3 days later, the a/c doesn't cool again. Same thing, had to go to attic to turn off blower fan. Since it's the weekend, we just let it set a few hours and it turned back on cool. Again 3 days later, it happens again. This time, we get someone else to look at it and he is confused while checking the circuit board in the attic why 24 vlts from transformer going to board but wouldn't exit to t-stat. That's why I couldn't turn blower fan off from t-stat. He unscrews it to look on the back, no burnt area, and after reinstalling it back up, we heard the freon starting up. Now, it's o.k. and outside unit is working. He says, the circuit board needs replacing. We are now waiting another 3 days to see if the same incident happens. I asked would a evaporator coil freeze up cause this. He said no. I asked because our evaporator coil is in the attic and it doesn't have an access door. It's a horozontal unit with air ducts on all sides and I don't think it's ever been serviced. I'm thinking nobody wants to do this job just to diagnose but to only replace it. Am I wrong in thinking this. I'm learning along the way. I just want an honest correct diagnosis.


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Old 06-07-2012, 12:39 PM   #2
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Obviously the most money to be made is with a new unit/system replacement but that's not to say we won't diagnose and repair an existing system. I do it quite often and I enjoy it.

As matter of fact I only yesterday took home a Lasko floor fan that my counselors office was throwing out, labeled as trash for the janitor. Due to my new found experience as a service tech over the past three years, comng from a decade of only installing hvac systems, I found the problem, a simple fuse on the control board which I unsoldered and soldered a new one on. Works like new.

Four years ago I would've been stumped and the fan would have made it to a land fill.

In other words, being a service tech, especially when new to the field, does not mean one comes to your door with a plethora of experience or the full data base of how to diagnose and repair. It takes time.

I say this because I don't believe for the first tech to fully understand what he was doing.

It sounds like you will be having trouble again soon enough. When you do please come back and tell us step by step what the unit is doing, where there is power and where there is not. Your furnace control board should have an LED light, When the furnace has an issue the LED will usually flash a code, that code is stated on a legend located in the furnace, most likely on the inside of the door. From there we can help you determine what is wrong and how to repair it if you so choose.

Good luck.


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Old 06-07-2012, 04:41 PM   #3
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look for a condensate over flow switch, or a wet switch. may have one that is doing its job due to a slow drain.
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