I have a Honeywell T6 Pro series thermostat, been working fine for about 4 years. Issue I have is when the Thermo calls for cooling the air handler fan won't start, but the outside heat pump starts. It is set to kick the unit on if there is a 1 degree variance. Lower it from 76 to 75 the heat pump starts but not the fan. In order to get the air handler to start I have to lower the set point 3 degrees, 76 to 73. When the temperature gets to 74 the air handler shuts back off but the heat pump continues to run. Also the fan will not run if I select "fan on" or "fan circulate" on the thermostat. I'm just guessing its the thermostat. Normally it "clicks" 3 times when it calls for cooling. 2 of the clicks are for the heat pump and one is for the blower. Now when it starts it only clicks twice, which starts the heat pump and when I drop it the other 2 degrees I get the third click for the blower and it starts. Any ideas? Thank You

This message has been edited. Last edited by: 08 Cayenne,

Not an AC guy, but recently had a similar experience with my American standard heat pump. Edited to correct, thanks ExCam!!>>>>Unit was not cooling but air handler running, outside unit was not running.

First attempt was to replace the "points" on the AC outside unit, as they looked like the could have welded themselves together. Reset the unit, set thermo to Auto and away we went. Lasted for about a day, and no cooling again.

Tech advised if it was anything but AmStd he would think it was the low pressure switch (like a circuit breaker that protects the unit) on the outside unit, as the same switch fits many brands, but he had never had one go out on AmStd.

He was fearful it was the motor on the air handler which has a "brain" on it that tells it when the Therm was calling for what. Over $800 for that motor and since it is pre-programmed for your unit, it belongs to you when bought regardless as to if that fixes the problem. He had another tech listen to the motor and they decided it was doing what it was supposed to do, so Yay on that.

He ended up wiring around or somehow bypassing the low pressure switch on the outside unit, and it then worked fine. So, it stayed like that for about a week until the new low pressure switch could get here and be installed. $80 for that switch was a whole lot better than that $800 motor that wasn't the problem.

So much for that switch NEVER going out on AmStd!!

You might try what he did to narrow it down, which was to turn the breaker off on the whole unit, for a minute or two. Set the thermo fan to ON rather than auto, power up the unit, see if it continues to run the outside unit with the fan in the On position. My would run fine with the fan set to On even with the bad pressure switch, plus I could get cool air. I have no idea why that worked like that but it did.

This message has been edited. Last edited by: BigWhup,

Only thing I can suggest is jumping out the tstat wiring to confirm it's actually the tstat. If everything works as normal then replace the tstat.

quote:

Normally it "clicks" 3 times when it calls for cooling. 2 of the clicks are for the heat pump and one is for the blower. Now when it starts it only clicks twice, which starts the heat pump and when I drop it the other 2 degrees I get the third click for the blower and it starts. Any ideas?

Click 1 = Compressor changeover valve - R/Rc connected to O/B via T-stat relay
Click 2 = Compressor - R/Rc connected to Y via T-stat relay
Click 3 = Air handler - R/Rc connected to G via T-stat relay

Sounds like it's only telling it to start when it's calling for 2nd stage cooling. Perhaps there is a setting in the T-stat that has changed?
All of those functions are controlled by the thermostat, sounds like the thermostat is bad. Also, although it's not a necessary test since you can get it to run by "tricking" it, if you jump R to G on the thermostat base and the fan runs, that's essentially all the thermostat does to start the fan...

When mine needs new batteries it does something like that.

What's the equipment information (make, model, serial)?

quote:

Originally posted by BigWhup:
Not an AC guy, but recently had a similar experience with my American standard heat pump. Unit was not cooling but outside unit running, air handler not running.

First attempt was to replace the "points" on the AC outside unit, as they looked like the could have welded themselves together. Reset the unit, set thermo to Auto and away we went. Lasted for about a day, and no cooling again.

Tech advised if it was anything but AmStd he would think it was the low pressure switch (like a circuit breaker that protects the unit) on the outside unit, as the same switch fits many brands, but he had never had one go out on AmStd.

He was fearful it was the motor on the air handler which has a "brain" on it that tells it when the Therm was calling for what. Over $800 for that motor and since it is pre-programmed for your unit, it belongs to you when bought regardless as to if that fixes the problem. He had another tech listen to the motor and they decided it was doing what it was supposed to do, so Yay on that.

He ended up wiring around or somehow bypassing the low pressure switch on the outside unit, and it then worked fine. So, it stayed like that for about a week until the new low pressure switch could get here and be installed. $80 for that switch was a whole lot better than that $800 motor that wasn't the problem.

So much for that switch NEVER going out on AmStd!!

You might try what he did to narrow it down, which was to turn the breaker off on the whole unit, for a minute or two. Set the thermo fan to ON rather than auto, power up the unit, see if it continues to run the air handler with the fan in the On position. My would run fine with the fan set to On even with the bad pressure switch, plus I could get cool air. I have no idea why that worked like that but it did.

An open or bad low pressure switch wouldn't allow the outside unit to operate.
And would have no effect on the indoor blower motors operation.

It simply opens and cuts 24 volt power to the outdoor units contactor.

Yep, I said it backwards. Air handler was running, not cooling, outside unit was not running.

Thank you all.

What you say makes all kinds of sense. I went thru all the settings and they are the same as when I originally set it up years ago. I'll try the jumper. I'm going to do a factory default reset then re-program it. If it still doesn't work I'll replace it. What doesn't make sense to me is why the fan on and fan circulate will not work on the tstat.

quote:

Originally posted by stoic-one:

quote:

Normally it "clicks" 3 times when it calls for cooling. 2 of the clicks are for the heat pump and one is for the blower. Now when it starts it only clicks twice, which starts the heat pump and when I drop it the other 2 degrees I get the third click for the blower and it starts. Any ideas?

Click 1 = Compressor changeover valve - R/Rc connected to O/B via T-stat relay
Click 2 = Compressor - R/Rc connected to Y via T-stat relay
Click 3 = Air handler - R/Rc connected to G via T-stat relay

Sounds like it's only telling it to start when it's calling for 2nd stage cooling. Perhaps there is a setting in the T-stat that has changed?
All of those functions are controlled by the thermostat, sounds like the thermostat is bad. Also, although it's not a necessary test since you can get it to run by "tricking" it, if you jump R to G on the thermostat base and the fan runs, that's essentially all the thermostat does to start the fan...

The air handler is a Lennox multi speed CBA27UHE 3 ton. The heat pump is a Lennox multi speed XP16-036-230 3 ton.

quote:

Originally posted by Excam_Man:
What's the equipment information (make, model, serial)?

quote:

Originally posted by 08 Cayenne:
The air handler is a Lennox multi speed CBA27UHE 3 ton. The heat pump is a Lennox multi speed XP16-036-230 3 ton.

quote:

Originally posted by Excam_Man:
What's the equipment information (make, model, serial)?

Multi-speed blower changes things a bit. "May" actually be an speed tap input on the motor. Does it "sound" like it's running faster/slower than normal when you do get it to run? Looking at page 13 here it's possible one of the speeds isn't kicking in. Could be either, so trying the jumper may have some merit...

Pretty sure it is a 2 speed air handler, I didn't get the variable speed because I had that before and it was very problematic. It always runs on high now, I thought due to the fact that I am setting the tstat to a much colder temp than the actual room temp. If the clicks are the tstat sending the air handler instructions then it sounds like the tstat. Because when I start it I get the 1st 2 clicks only and don't get the 3rd until I drop the temp more. I know nothing though of how these things are supposed to work.

quote:

Originally posted by 08 Cayenne:
The air handler is a Lennox multi speed CBA27UHE 3 ton. The heat pump is a Lennox multi speed XP16-036-230 3 ton.

quote:

Originally posted by Excam_Man:
What's the equipment information (make, model, serial)?

2 stage equipment...

The third click is bring the unit to full capacity.

quote:

Also the fan will not run if I select "fan on" or "fan circulate" on the thermostat

With both symptoms, more than likely a bad blower relay in the air handler.

Thank You Sir, I think you are correct. Does this require a complete motor change or can just the relay be changed?

quote:

Originally posted by Excam_Man:

quote:

Originally posted by 08 Cayenne:
The air handler is a Lennox multi speed CBA27UHE 3 ton. The heat pump is a Lennox multi speed XP16-036-230 3 ton.

quote:

Originally posted by Excam_Man:
What's the equipment information (make, model, serial)?

2 stage equipment...

The third click is bring the unit to full capacity.

quote:

Also the fan will not run if I select "fan on" or "fan circulate" on the thermostat

With both symptoms, more than likely a bad blower relay in the air handler.

The relay is separate.

The motor always has 240 VAC.
L is L1 (120v)
N is L2 (120v)
G is GRND

Then you should have 24 volts to the motor on a call for cooling.
C terminal being 24v NEG.
Y1 first stage (24v POS) wired to one terminal (1 through 5).
Y2 second stage (24v POS) wired to another terminal (1 through 5).

Either the first stage power isn't getting to the motor tap or the motor is faulty.
If the motor tap is being powered (24 VAC) and fails to run, then it would require a new motor.

Thanks again. I have a tech coming next week.

quote:

Originally posted by Excam_Man:
The relay is separate.

The motor always has 240 VAC.
L is L1 (120v)
N is L2 (120v)
G is GRND

Then you should have 24 volts to the motor on a call for cooling.
C terminal being 24v NEG.
Y1 first stage (24v POS) wired to one terminal (1 through 5).
Y2 second stage (24v POS) wired to another terminal (1 through 5).

Either the first stage power isn't getting to the motor tap or the motor is faulty.
If the motor tap is being powered (24 VAC) and fails to run, then it would require a new motor.

Out of curiosity, would you share with us what the problem/solution was?

Thanks

The tech came Tuesday and said the blower module is bad. Also found some wires loose, on the Y1 & Y2 screws, they were yellow wires. He didn't test anything though just said this is normally what goes bad. He is coming back this afternoon to install the new module.