Bob and Tim were on their way to the shop on a hot Friday afternoon when Bob got a call on his cell phone from his wife who said, “The air conditioner is not working and my mom and dad are coming from out of town tonight. What are we going to do?”

Bob said, “I will be home within the hour and see what I can do.”

Tim asked, “Do you suppose that the company will allow you to drive your truck home? I know they have a rule that all trucks must come to the shop for the night. What is that all about anyway?”

Bob explained, “There is a big temptation for service technicians to use the company truck to run their own service calls at night. It has happened to lots of companies. There is no temptation if the technician doesn’t have a company truck. Technicians have been known to tell a company customer that they will be back after quitting time to fix their unit and pocket the cash. That is not ethical. There are no problems if the truck is in the company lot, locked up. I don’t even want to ask so I will take my chances that I can repair my unit without the truck. I have some tools and equipment of my own at home. Will you go with me and help me see what I can find?”

Tim said, “Sure, I will probably learn something.”

When they got to Bob’s house, they went inside and Tim said, “It sure is warm in here. You may have to go to a motel with your young baby and in-laws tonight.”

Bob talked to his wife and she said, “I started noticing it getting warm about 4:30 and noticed the indoor fan was running, but the indoor air registers were putting out room temperature air.”

Bob said, “We will get right on it.”

They went to the condensing unit and Tim said, “The fan is running, but I don’t think the compressor is running.”

Bob said, “I agree. Let’s take off the control box cover and see what we see. If the fan is running, the thermostat is sending a signal to the condensing unit. That means the controls are calling for cooling. Take a look around and see what you see.”

Tim said, “Look at that hard start capacitor. The whole top is blown off of it (Figure 1).”

Bob said, “The compressor should be able to start without that hard start kit. It was put on there at startup to help the compressor when it was new, during the break-in period. After it has run for a while, the compressor should start without it. Just turn off the disconnect and let’s just take that out of the system.”

Tim turned off the disconnect and removed the hard start kit and asked, “Now what?”

Bob said, “While the disconnect is off, reach in the unit and see what the compressor feels like. Touch it lightly. It may be hot.”

Tim touched the compressor and said, “You are right. It is hot.”

Bob said, “Let’s let it cool for a few minutes and check the motor windings with an Ohmmeter. Tell me what it reads from common to run and common to start.”

Tim did the Ohm check and said, “It shows an open winding from common to run and start.”

Bob then said, “Check the run terminal to the start terminal and tell me what that reading is.”

Tim checked from the run terminal to the start terminal and said, “It reads 21 Ohms. What is going on?”

Bob said, “It looks like the internal overload is open (Figure 2). At least let’s hope that is what is going on. Let’s let it cool for a few minutes. Meanwhile, look at the combination compressor and fan capacitor.”

Tim said, “It is all swelled up on top (Figure 3). I wonder if it is good. I will get the capacitor checker and check it. Oh man, we don’t have the truck. What are we going to do?”

Bob said, “I have an old analog volt-Ohmmeter. We can use the RX1 scale on it. Short the terminals together with a screw driver to make sure the capacitor doesn’t have any charge in it and watch.”

Bob put one meter lead on the common terminal and the other on the compressor terminal (labeled hermetic) and the needle didn’t move. Then he kept the lead on the common terminal and placed the other lead on the fan terminal and the meter needle didn’t move. He then said, “The capacitor is definitely bad. I am not sure what to do now. The supply houses are closed for the weekend. I know one large supply house that has a national number. Let me see what I can do.”

Bob called the national supply house number and to his surprise someone answered. He explained the situation and the operator took down the specs on the capacitor, 50mfd-7.5mfd and 370 volts. She said, “The store in your town does not have that exact capacitor, but it has a 50mfd-7.5mfd and 440 volts. Will that work?”

Bob said, “Yes, the higher voltage rating would work. The capacitor may be larger, but we can work around that.”

Then she said, “There may be one catch. We charge $50 for getting someone down to the store and opening it afterhours. Is that good with you?”

Bob said, “It is either that or take my family to a motel. I will take it. What do we do next?”

She said, “I will take your number and our store person will call you within 45 minutes. They will go to the store and pull the part to make sure they have it and call you.”

Bob told Tim that he might as well go home. There was going to be some waiting time.

Tim left and, in about 15 minutes, Bob got a call from the counter man from the store and he said, “I am sure we have the part. I am on my way to the store for another customer, so come on over.”

Bob said, “It will take me about 30 minutes.”

Bob got to the store and the counter man met him with the part. Bob paid for it and was on the way home. When he arrived, he replaced the capacitor and closed the disconnect and the compressor started. About that time, his wife’s parents arrived and he explained what had happened. His wife was really glad.

Bob called Tim and explained how smooth everything went. Tim said, “When I saw the call was from you, I thought it would be bad news. I am glad for you all that it worked out.”

Publication date: 8/17/2015

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