Troubleshoot properly to avoid wasted time and energy.

I spent the summer in my basement. It wasn’t the coolest spot -- actually the rest of my house was colder. That was the problem. I was troubleshooting my air-conditioning system. Where I live, in Colorado, heating and air-conditioning equipment is in the basement. Troubleshooting took all summer because I did it wrong.

I was doing it wrong just like anyone might. I didn’t follow a troubleshooting process. I skipped all around. I made assumptions. I replaced parts. I took advice.

Troubleshooting is a process. You have to start at the beginning and do all the steps without skipping any. If you do that, you’ll find out what’s wrong. If you don’t, you’ll just waste a lot of time.

Here’s how I set myself up to spend my summer troubleshooting in the basement. See if it sounds familiar. You wethead hydronics folks are going to be tempted to say “serves ya right” for having forced air, but hey, it came with the house.

I had added forced air zoning to my heating and air conditioning system. Like hydronic zoning, it makes it possible to deliver different amounts of heat (or cooling) to different parts of the house. I can’t blame my troubleshooting problems on zoning. I have to blame them on my not following the troubleshooting process.

My zoning system worked fine at first. There are six zones -- a truly over-zoned home. Any one can call for heating or cooling whenever it needs it. The dampers for that zone open, while all the others close. The dampers and thermostats for those six zones are wired into two electronic zoning panels, three zones on each. The panels are wired together so that they think as one brain.

All was fine until the lightning storm. After the storm, when any one of the first three zones called for cooling, that zone plus the last three zones cooled. When any of the last three zones called for cooling, nothing at all happened.


Getting Started

I called the 800-number technical hotline. They had me check lots of voltages with my meter. Everything checked out.

“Well, bad news,” they concluded. “You need to replace the number one panel.”

I remarked, with a big sigh and a chuckle, “So it took us an hour to get where most of us would like to start anyway -- just change the electronic panel!”

Here’s a routine you’ll recognize. I drove to the supply house, picked up a replacement panel, and killed a couple more hours talking to people I know. I got back to the job, labeled all those wires on the panel with masking tape, removed all those wires from the first panel, re-wired all those wires to the replacement panel, crossed my fingers, turned the power on, and voila, nothing had changed.


So I removed all the wires from the replacement panel, re-wired them back to the original panel, and put the replacement panel back in the box. That about killed the day.

Next day, back to the hotline. “Hummm. Let’s check those voltages again. Yep. If it’s not the first panel it’s just gotta be the second panel. Replace it.”

Sooo, bigger sigh this time, because I really knew how much time this was going to take. But if it’s what I have to do ...

I drove to the supplier again, but they didn’t have that panel. I drove to a second supplier, got the panel, took it to the job, labeled all the wires on the second panel, unwired the second panel, rewired onto the replacement panel, crossed my fingers, held my breath, turned on the power, and nothing had changed.

You know what I did next and how I felt about it. Another day killed.

Out The Window

By now I’d completely forgotten everything I may have ever known about good troubleshooting process. I started asking for advice. I asked everybody, and I got a lot of sympathy. The consensus was to change the transformers.

I got two new transformers. I remembered the rule to never work alone with line voltage if at all possible, so I reviewed with my teenaged daughter what to do should she find me electrocuted (here’s the wooden broom handle. Touch me only with this, and call 911). She threatened to leave home until I got my sanity back.

I shut off the basement circuit breakers, went to the basement, found everything dark, went back up and turned the circuits back on, and returned to the basement to find the trouble light and a long extension cord. I plugged the cord into a non-basement circuit, shut off the basement circuit breakers again, and followed my shaky trouble light back to the basement. This stuff takes forever!

Down at last to the task of changing the transformers. I labeled wires, changed the transformers, and rewired them to the panels. I turned on the circuit breakers, applied power to the panels, held my breath, looked heavenward, and -- ta-dah! -- nothing had changed.

Out of ideas and advice, I continued to control my cooling by blocking registers with piles of books.

Many weeks later I was having a phone conversation with my troubleshooting zoning-guru friend John. We were commiserating about how really strange this problem is. And we realized -- finally -- that I didn’t start at the beginning of the troubleshooting process.

So I got on my cordless telephone headset with John in California on the other end of the line, and here’s what we asked:

  • Is there a call for cooling? (Is the thermostat switch closed/turned on?) Yes.

  • Is there at least 24 volts (V) coming into each of the two panels from the transformers? Yes.

  • Is the system working properly? No.

  • Do the panels work properly with nothing attached to them? Don’t know.

Don’t know?!

You mean I did all this changing of parts and I don’t know if the panels work?!

OK. One more time I made sure all the wires were labeled, and removed all of them from the panels. (Oh no, oh no, oh yes.) Moving on ...

  • I put 24V back on the panels. I checked to make sure it’s still 24V. It is.

  • The LEDs on the panels showed that the panels are powered. (LED means light-emitting diode. In electronics a diode is a component that makes sure electricity can go only one way in a circuit. A light-emitting diode makes light as well.)

  • I connected the zone 1 thermostat to the panel.

  • I connected the zone 1 motor to the panel.

  • I asked, on a call for cooling from the thermostat, does the motor activate? Yes.

Let’s pause for a minute here. The problem all summer was that when any one of the first three zones (all on the first panel) called for cooling, cooling was also delivered to all three zones on the second panel, even if they didn’t want it.

  • I connected the first panel to the second panel, and called for cooling for a zone connected to the first panel, in order to see what happened on the second panel. Nothing. That’s good.

    So I had new and important information. When everything was removed from the panels except power, the zone 1 stat and the zone 1 motor, both panels worked properly. This told me that I didn’t have a bad panel or transformer. (Wish I’d known that at the beginning of the summer!)

  • I added the zone 2 stat. Both panels still worked.

  • I added the zone 2 motor. The LEDs on the second panel went crazy -- just like they’d been doing all summer. They flashed green and red and even kinda pink. Then they settled down to showing cooling for all three of those zones.

So the problem was isolated. There was something about the zone 2 motor that made the second panel go nuts.

The problem had to be that zone 2 motor. Luckily I had a spare. John got off the phone, and I ran to the garage to get my spare motor.

It was about 10 p.m. -- hardly the ideal time for working with tiny screws in tight spaces. But you know that. Just about the time I dropped the second screw from the old motor, I noticed a damaged spot on the insulation of the wire coming into the motor. It looked like the wire might be shorted. This was in a place that I never would have seen if I hadn’t been trying to get positioned to remove that motor.

Could that be it? Was that little piece of damaged wire the cause of a whole summer’s worth of problems?

You can imagine how I wished I’d seen that damaged spot before I removed (and lost) those two motor screws.

To end a long story quickly, I cut out the shorted section of the wire and, just for good measure, replaced the motor. I held my breath, crossed my fingers, turned on the power, created a call for cooling on the first zone, and yes! the system worked perfectly.

Whatta shame. All that parts changing and wiring and rewiring, all because I didn’t find -- or even look for -- a damaged wire.