Home Heating/Cooling unit question

[ehenry]

I have a Trane central heat/air conditioning system in my house. When the a/c sytem is on the compressor unit out side comes on and runs fine but the inside blowing unit will not run. Same for the heating side of the system. It is a gas heating system. When the thermostat is turned to heat the burners in the system light and burn fine but the blower unit does not come on. There is a flashing LED on the inside of the unit along with a list of the codes. The LED is flashing slow and steady while system is set for A/C. The list says this is "Normal No Call For Heat'. If I switch the system to heat it flashes steady and fast the list says "Normal No Call for Cool".

Any ideas??

 

[Barnacle_Bill]

Re: Home Heating/Cooling unit question

That happened to me with my heat pump. When I took the cover off the unit I found a wire burn't in two and was able to repair it. I suspect a loose connection caused the problem.

 

[SS MAYFLOAT]

Re: Home Heating/Cooling unit question

It could be a couple of things. I'm suspecting a bad blower or the capacitor on the blower. When in cooling mode, the blower should come on as soon as the condenser unit out side comes on. During the heat mode, usually there is a fan limit switch that heats up (when the burners are on) to a set point before turning the blower on. Some models will have a stat on the coil so that the fan comes on only when the evap coil has reached a set point. I haven't seen many units set this way except for refrigeration units.

With you saying that the blower doesn't come on for the AC, tells me that it can be the blower, bad wire, or a capaitor. With the unit off, reach inside and see if the squirrel cage turns freely. If it is hard to turn,,,,,,more than likely the blower needs a new motor. If it turns free, you may need to have the capacitors checked along with making sure it is getting voltage.

Some control boards will not sense if the blower is actually running. If you leave the heat on without the blower running, it should kick off on its high limit. If it (the burners) does kick off on high limit, the board should show an error code.

BTW, most Trane units will have their own specs for the blower. This makes it hard to find a generic replacement.

 

[ehenry]

Re: Home Heating/Cooling unit question

I've reached inside the unit and the squirrell cage turns freely theres no sign of burned wires. WHen you depress the safety switch it sounds as if the unit tries to come on. You can hear several clicks then a soft buzz.

There is a starting capacitor on blower motor. I do not know how to check a capacitor. I do, however, know that a capacitor will knock your tally wacker in the dirt if you dont watch what you're doing.

This unit is amost 9 years old. This is the first problem.

 

[SS MAYFLOAT]

Re: Home Heating/Cooling unit question

There are cap checkers that can test them. Without one, it would be hard to tell if that is it or not. With the buzzing going on, sure sounds like a cap to me. Is it a belt driven or direct drive motor? Do you by chance have a VOM meter to see if it is getting the line voltage?

Usually when I change out a motor, I'll change the cap regardless if it is bad or not. So maybe getting a new capacitor and trying that first. If it has line voltage still with the buzz,,,,,,probably the motor itself. A generic cap will work providing the specs are the same. Hope this has helped.

 

[ehenry]

Re: Home Heating/Cooling unit question

The motor is direct drive. I do have a VOM.

ANy other words of wisdom?

 

[Xcusme]

Re: Home Heating/Cooling unit question

SS Mayfloat is right....replace the cap...on a 9 year old system, buzzing, sure sounds like the most likely item. The start/run caps are cheap. You can check the cap(s) you have with either an analog or digital VOM.
Destructions here:
hxxp://www.wikihow.com/Check-a-Start-Capacitor

Just change the xx's above to tt's.

 

[ehenry]

Re: Home Heating/Cooling unit question

I pulled the starting capacitor and tested it according to the web site Xscusme listed above. With the VOM set at 1K ohms the needle does not jump to 0 and fall back like the directions say it should after you swap them between the two terminals. The needle reads as if you touch the two probes together. Does this mean I need a new capacitor?

If you set the VOM to 10K Ohms the needle jumps to 0 then falls back to infinity.

I'm confused........

 

[whywhyzed]

Re: Home Heating/Cooling unit question

If you set the VOM to 10K Ohms the needle jumps to 0 then falls back to infinity.

I'm confused........

The battery in your meter is charging the capacitor, so it reads zero because the cap is acting like a dead short until it gets "full". Then it won't take any more charge so your meter reads infinity.

An ohm meter is really a calibrated ammeter with it's own power supply (batteries in the meter)

It sounds like your cap is ok to me from that test, but I can't imagine they're more than a few dollars, so I would put a new one in.

How did this problem start? Worked fine one day and not the next?
Or, was it acting up on and off for a while?

 

[SS MAYFLOAT]

Re: Home Heating/Cooling unit question

The leak down test above only tells if the cap is charging/discharging. It won't tell if it is charging up to its designed specs. Usually it is a +/- 5 to 10% of its value. If it is out of those brackets, it will not work properly.

First I would follow the wires from the blower motor back to the board. Unhook those wires and set you meter on volts. Put your leads on the terminals on the board for the output to the blower. Then hit your button. You should get line voltage reading 110 to 120 or so. If it is less than that, you may have a bad icecube relay or triac (on the board) that is not functioning properly.

If you do have line voltage, and the changing of the cap does not work,,,,,,pull the motor and take it to a repair shop if you want to confirm that it is bad. Sometimes Grainger has drop in motors for Trane units.

 

[ehenry]

Re: Home Heating/Cooling unit question

Problem solved - I had to give in and call a local H&C guy. He's determined it was a control board. He bypassed the board to determine is the blower motor was good and it was. He located a board in Jackson and will be back at the house this afternoon to install.

THanks to all who replied.

 

[tomatolord]

Re: Home Heating/Cooling unit question

that was the same thing that happened to my control board - it went bad and would not turn the inside blower on.

They have an override to just leave the blower running - which is ok until they can get the board in place - that way when the heat comes on it works, which beats a cold house.

tomatolord

 

[arboldt]

Re: Home Heating/Cooling unit question

Sounds like you've identified and fixed the problem.

Before I got down to that point in the thread, though, I was going to suggest trying the fan only -- most thermostats or furnaces have a switch for the fan to run continuously. My wife and I usually have the fan on that continuous setting because she has this thing about air circulation. Anyway, turning on just the fan would have told you if it was in the fan / capacitor or in the controls. But you know that now.

Enjoy.