Hvac troubles

Catfish

Catfish

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My old gas pac is hiccuping yet again. On heat mode it works great. Fan blows normally.

On cool mode the fan runs a few minutes, stops, runs a few more minutes, then stops, and the compressor keeps running with no fan. It eventually shuts off and repeats this. When it blows, the air is cool.

Anyone have an idea where i should look for this gremlin?
Fan capacitors were replaced last year.
I havent checked for an error code yet
 
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Catfish said:
My old gas pac is hiccuping yet again. On heat mode it works great. Fan blows normally.

On cool mode the fan runs a few minutes, stops, runs a few more minutes, then stops, and the compressor keeps running with no fan. It eventually shuts off and repeats this. When it blows, the air is cool.

Anyone have an idea where i should look for this gremlin?
Fan capacitors were replaced last year.
I havent checked for an error code yet
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You may have another capacitor problem (yes they are that bad now) or the fan motor is getting hot and stopping until it cools again.
 
You should amp probe the fan. See if it's draw over amp just defore it shuts down or if it losing voltage completely.
Over amp would show problem with fan motor/ cap. No voltage shows problem with controller or contactor.
When it off , does the motor turn smooth easly? When it starts does it struggle / loud humming coming up to speed?
 
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BlackGun said:
You may have another capacitor problem (yes they are that bad now) or the fan motor is getting hot and stopping until it cools again.
Click to expand...

BlackGun, I always learn something from your posts about HVAC problems. Thanks for sharing your knowledge.
 
Cooling probably runs on high speed while heat uses medium or low. Could be a connection at the control board or could be board going. Bad. Also could he high speed going out on motor. If motor runs fine in heat then prob not a capacitor problem
 
It runs fine on the fan only cycles too, 15 min/hr
 
Ok im giving it a workout today and everything runs as it should. No struggles, stops or hiccups. Weird.

According to the wiring diagram the blower red(heat) and orange(m3) leads are switched. They are plugged into the board opposite that. How much weight do you give that diagram? The
 
Catfish said:
Ok im giving it a workout today and everything runs as it should. No struggles, stops or hiccups. Weird.

According to the wiring diagram the blower red(heat) and orange(m3) leads are switched. They are plugged into the board opposite that. How much weight do you give that diagram? The
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Don’t worry about that. Red is low speed for heat mode. Orange is pugged to a spare terminal which does not have an output. It’s just a place to put the spare speed. If no wiring has been changed then you don’t need to make changes now.

what is the manufacture date and what brand name?
 
Scsmith42 said:
BlackGun, I always learn something from your posts about HVAC problems. Thanks for sharing your knowledge.
Click to expand...
Glad to share if I have enough info. Hard to pinpoint issues without being on site. At the same time I learn something every day myself. I have gained a lot of knowledge from guys on here about other trades, equipment, and vehicles.
 
Not exactly sure when it was installed. Well over 15 yrs ago.
 
Yes we did, 5yrs ago?
Its also had a new heat exchanger, gas valve, pressure switch, and a few other items. Its like grandad’s axe.
 
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To find out if the indoor fan motor speed on cooling is a problem:
1. If the unit runs fine in heat but cooling speed winding is bad- if the black wire is landed on the cooing terminal on the board then take it off and put the blue wire on that terminal coming from the fan motor. Do this by cutting off the power to the unit with the breaker and then put electrical tape on the black wire or place it on an empty M1,m2, or m3 terminal. This will eliminate the speed winding issue internal to the motor. The unit literature shows the blue speed is high enough for the 4 tons of cooling. Unless you have inadequate duct sizing you should be fine.

*Note- if you have a pigtail jumper that makes the red wire be both the cooling and heat speed then that jumper must be removed.

2. If this doesn’t correct the issue you most likely have a motor issue or a component issue on the board.Motor will be 90 percent more likely.

3. Your unit is 4 tons of cooling and 120,000 btus of gas heat. Your heat will come on and go off much faster than the cooling mode. This may be why the heat side never sees a motor failure. It never runs long enough for the motor to fail. 120,000 btus is a lot of heat. The circulation mode of the fan is a lower speed. It is not the higher speed available for cooling.

**Note: For all those who live in a modular homes. These homes have very small ducts. It takes a high static fan indoor unit to overcome these small ducts. A regular air handler from name brands are usually not rated for these homes. There are a few that will work but there is not many. Yes someone will claim it does and will install them but usually they don’t understand the static pressure requirements and the lack of distance from the exit point on an air handler to the duct surface. Do not install a larger heat pump or A/C than the duct can handle. Bigger is not better.

http://enora.nortekhvac.com/Literature/7086290.pdf

Go to page 18 for the wiring and board diagram.
 
Thanks for the education. To recap, for this test I should remove the jumper and place the blue wire on cool, and then call for cool and let it run... 15 min or so?

My home is 2100 sf two story with this unit serving it as one zone. The trunk goes across my crawl, branches up to the attic and then feeds the upstairs rooms with an ductwork octopus.

Our long term plans include replacing this with two units but im not ready to pull the trigger on that yet...
 
jjwestbrook said:
Looks like you are using same speed for both. Orange wire. Note the red jumper between heat and cool.
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What @jjwestbrook said. That picture gives much more info. The orange wire is low medium on heat then jumped to cool. The red wire that is a couple inches long is no more than a way for one speed work on both modes.

I hope you’re not confusing a fan not running by the floor register output. A frozen evaporator coil blocking the fan flow is much different than you saying the fan is not turning. Verify the motor is not turning. Put the fan switch into continuous fan and heat and cool off. See if it runs for an hour. Report back.
 
BlackGun said:
I hope you’re not confusing a fan not running by the floor register output.
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I don't think I am. When I noticed the lack of air flow with the AC compressor still running I switched it over to heat and also to fan only and observed normal air flow with both.
When I did the same thing while standing next to the unit I observed the evap coil fan spinning when I called for cool. I don't see any ice on the coil looking down from the top. I didn't open it tho.

ETA or am I showing my ignorance here? Is the evap coil even visible from outside the cabinet?
EETA - google says yes, I am. I still don't think +air/no-air/+air/no-air sequence adds up to a frozen coil, but I learned something.

BlackGun said:
Put the fan switch into continuous fan and heat and cool off. See if it runs for an hour.
Click to expand...
I did this and then lost track of my hour. I'll try again and report back.

Thanks for the help guys.
 
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Catfish said:
I don't think I am. When I noticed the lack of air flow with the AC compressor still running I switched it over to heat and also to fan only and observed normal air flow with both.
When I did the same thing while standing next to the unit I observed the evap coil fan spinning when I called for cool. I don't see any ice on the coil looking down from the top. I didn't open it tho.

ETA or am I showing my ignorance here? Is the evap coil even visible from outside the cabinet?
EETA - google says yes, I am. I still don't think +air/no-air/+air/no-air sequence adds up to a frozen coil, but I learned something.


I did this and then lost track of my hour. I'll try again and report back.

Thanks for the help guys.
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Impossible for you to see the evaporator coil or blower fan to run without taking the side cover off. You are looking at the condenser fan if it’s viewable without taking screws out and panel off the side. So now we need to decide if you are talking condenser fan or evaporator blower motor. When heat from the gas furnace runs it will quickly melt the ice off an evaporator coil with 120,000 btu furnace.

look at the literature I sent and find the correct panel to access the motor and coil section. Pull the panel after running the unit at a low temp setting so it continually stays on for more than 30 minutes. Check to see if the blower motor is turning fast. Observe the coil for frost. Low refrigerant will ice up the coil and block output air.
 
Unit has been on heat mode for the last 8 hours

11:44 Call for cool. Unit starts blowing air right away, its cold inside 30 seconds, air flow is strong.
11:45 Air stops. I can still hear something running, but air stopped moving. No error code at the board.
11:54 cold air flow resumes
11:55 and it stopped for 10 seconds, runs 10 seconds, stops
11:58 Switch over to fan mode and its blowing fine.
12:10 subbed the blue wire for the orange one. Called for cool. Running
12:12. Stopped. Same behavior as above.
 
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Catfish said:
Unit has been on heat mode for the last 8 hours

11:44 Call for cool. Unit starts blowing air right away, its cold inside 30 seconds, air flow is strong.
11:45 Air stops. I can still hear something running, but air stopped moving. No error code at the board.
11:54 cold air flow resumes
11:55 and it stopped for 10 seconds, runs 10 seconds, stops
11:58 Switch over to fan mode and its blowing fine.
12:10 subbed the blue wire for the orange one. Called for cool. Running
12:12. Stopped. Same behavior as above.
Click to expand...
1. If you place the thermostat in the ON position and it runs for an hour with no stop you have eliminated the fan as an issue.
2. If you place it in auto and check 24v (as high as 30v possible) from common to the green wire coming from the thermostat it should maintain voltage without interruption. If it does not replace thermostat due to fan AUTO circuit no good.
3. If both of the above prove good you have a bad board most likely.You can see if motor voltage is delivered constantly by using a voltage meter on the line voltage wire going the motor and the orange wire or terminal on the board. That would be 230v. If you don’t have multimeter skills find a friend who does.

Note: when something operates normally and then later fails over time that indicates when a component on a board has power applied and amperage present heat from a bad component separates the flow thru the circuit.

Note 2: Use caution changing out a thermostat. All thermostats are not alike. Programming can be complex if you don’t understand how the system operates.
 
Good info thank you.
I put the system in heat mode overnight. That way it remains "off" but runs the fan 15 minutes every hour. as far as I could tell this worked fine, but I have not done the 1-hour run test yet.

I have some middlin' multimeter skills so I think I can do those checks.

My thermostat is a Nest E. Any thoughts on that?

It wouldn't surprise me at all if it turns out to be the board. it's on it's third one since I've lived there.
 
Catfish said:
Good info thank you.
I put the system in heat mode overnight. That way it remains "off" but runs the fan 15 minutes every hour. as far as I could tell this worked fine, but I have not done the 1-hour run test yet.

I have some middlin' multimeter skills so I think I can do those checks.

My thermostat is a Nest E. Any thoughts on that?

It wouldn't surprise me at all if it turns out to be the board. it's on it's third one since I've lived there.
Click to expand...
My thoughts on a Neat thermostat is I don’t like them. It would take too long to tell the reasons why? I suggest if you ever buy another comfort system stay away from Nordyne. When suppliers volunteer to drop the brand you know it’s bad because they rarely let brands slip away.
 
Nest was an answer to one-zone two-floors. You can only really be comfortable in one spot with this thing. Everywhere else is too hot or too cold. Nest makes a wireless remote sensor that lets me move the "comfortable" area around.

I'll be collecting quotes soon. Can you recommend a brand? Do you want to quote it?
 
With AC running orange to common reads steady 240v. Every couple minutes a relay on the board click-click-clicks, voltage drops and returns, system is chugging on. Odd.

I cant figure out the Tstat voltage. Cant get a reading on anything. Meter might not be working in DC
 
Catfish said:
With AC running orange to common reads steady 240v. Every couple minutes a relay on the board click-click-clicks, voltage drops and returns, system is chugging on. Odd.

I cant figure out the Tstat voltage. Cant get a reading on anything. Meter might not be working in DC
Click to expand...
The thermostat voltage is AC, not dc.
 
Tstat voltage reads steady 27v while the board relay is shutting off momentarily. I think i have my answer. Installing a new board now...


ETA new board did not fix the problem. Compressor is running, fan volts at 0v, tstat green wire at 27v
 
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Swapped out the tstat for a dumb one and AC has been running for the last hour humming along with no hiccups. Guess I have a backup board now...

Im learning a lot from this but it still looks like you need to be either a magician or a parts swapper to work on these things.
 
Catfish said:
Swapped out the tstat for a dumb one and AC has been running for the last hour humming along with no hiccups. Guess I have a backup board now...

Im learning a lot from this but it still looks like you need to be either a magician or a parts swapper to work on these things.
Click to expand...
Nest thermostats are to complex for home owners. Simple is better. The unit most likely was running in constant circulation program where it runs then shuts off for a period. All heat pumps need to run in auto fan mode. It’s not necessary to have the fan on continuously or circulation mode. Maybe if there is an issue with deviation in temps from room to room but that is a issue with duct incorrect sizing or closed doors on rooms.

While I was mowing grass I thought of this thread when last night I saw where you stated the fan dropped out on timing. Glad you have found the issue. You are correct that heat pump issues take some higher knowledge which takes years. Too many variations in units and thermostats. I have put in thermostats that were so complex it took a engineer to get it correct. People wonder why there bill is so high now. Government involvement is the answer. Save the planet and triple the cost to repair one.

When I put in a comfort system for someone over 55 years old I put in less complex systems and thermostats. I also program the thermostat with high and low temperature limits they cannot go above and below. Sure I could make service calls due to lack of knowledge but I want them to go into retirement with low issues and less things they need to know. If you retire there is no need to have a programmable thermostats. Walk on over and turn it up or down. They’re home all day. What’s the benefit of having settings for leaving for work when you don’t work?
 
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Simple does not do it for me. I've been bending computers to my will since the Commodore 64. I want all the features.

We've been relying on the re-circulate function for years to compensate for a poorly designed system. It's a huge deal for this house and until I can get an upgrade I won't do without it. This Nest worked great for +/- 4 years until it started doing this voodoo crap. We lost another one to lightning and this one probably suffered he same. I guess it's time to shop again as I'm sure there are more options available now.

I want one that does:
- self-programming/learning mode
- optional wireless remote sensors
- ability to program the system to switch between the remote sensors on a schedule
- heat. cool, heat+cool, fan only modes
- periodic re-circulation when idle.
- wireless with an app
- works with Alexa
 
We’ve been a Nest household since Gen 1. :)
 
Ok I have 5 wires and the blue is connected to the C terminal on the board, but it has no voltage. Even at the board, that terminal is 0 volts.
Is it crazy to add a 24v transformer to power the thermostat?


I just figured out how dumb that sounds and what it does. C wire is a ground that allows the battery in the Nest to charge. testing continuity now...
 
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Is it possible to run a new wire from the board to the thermostat? Oh, I just reread your post and now I’m lost.
 
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Connect blue on thermostat. Connect blue wire from thermostat to common on low voltage side to the board. Should have 5 thermostat wires on screw terminals on the board which is in the lower right side of the board. Without being on sight I can’t see what is landed at what location.

For future info- the red wire provides circuit power to green, yellow, and white thru the electronics in the thermostat. Blue is common for a return electric path.
Red is hot from the 24 volt from a transformer which reduces 240v down to 24v control voltage.
Yellow power the compressor contractor
White powers the relay turning on a furnace
Green powers the relay for the fan.
Orange or blue is used most of the time for heat pumps. In that case I use brown for all common connections.

Note: Never make assumptions about colors. An installer may pull wires as he wishes. Verify where each wire has been landed or it will short out the transformer and at the very least blow the 3 amp fuse on the board or an independent fuse holder. Never replace a fuse with a larger rated fuse.
 
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