Heat Pumps and Electric Heating - blower motor will not start for heat pump / air conditioner

Not quite sure I am posting this in the right section.

I have a gas furnace (Amana) and then recently upgraded our air conditioning to give us both air and electric heat pump (american standard) for a hybrid system. The thermostat is a fancy one that has the settings of air, heat (uses heat pump above 35 degrees) and emergency heat (uses gas).

The blower motor works when using emergency heat. The blower motor does not work when using heat pump, air conditioning or fan set to on.

The outside unit's fan does turn on when trying to use air conditioning or heat pump.

In February, I replaced my blower motor and capacitor. A couple of years ago I replaced the controller board (Robertshaw HS780). There are no lights on the controller board.

I am not quite sure what is supposed to tell the blower motor to turn on. Since the blower motor comes on with gas heat, the controller board should be ok. I am thinking the issue is the fancy thermostat.

Thanks for the help.

Brian

Just to clarify you've had this issue for several years such that you've not been able to use the heat pump at all?

My gut likewise says you have a bad thermostat. It is worth checking to verify anyway. If you have a voltmeter we can help diagnose that. Just let us know what make and model.

I apologize for the slow response.

The thermostat is a Carrier dual fuel thermostat. 997-970210-3.

I gave a little bit of repair history for the Amana furnace that made it sound like the issue has been around a long time. The issue just came up in the last week or so.

Some additional information about the equipment
Amana Air Command 90 - Model GHN 115a50
American Standard Air - 4agh4036a1000ab

Thanks for the help.

Brian

Can't seem to find an exact manual on that model. Check to see if that's not a serial number.

Regardless, since you say one symptom is your fan switch doesn't work, throw the switch and check for 24VAC across G and C terminals. Here (http://wiki.xtronics.com/index.php/Thermostat_signals_and_wiring) is a map of standard color and terminals. Check out the diagram to better understand how the fan switch should work.

Let me know what you find.

I started searching the web for that id and could not find it. I checked the carrier website and saw all their thermostat part numbers started with TSTAT. I cracked open the thermostat and found it.

TSTATCCPDF01-B

The carrier web site does not include a manual for this thermostat.

I did find a manual at the site:
Untitled Document (http://www.favret.com/equip_files/thermostats.html)

Then search for product id.

I started searching the web for that id and could not find it. I checked the carrier website and saw all their thermostat part numbers started with TSTAT. I cracked open the thermostat and found it.

TSTATCCPDF01-B

Yes, that is the model I thought you had. Throw the switch, check for 24VAC across G and C terminals, and let me know what you find.

I appreciate your patience on this.

It appears the thermostat is working. Both 24VAC (HOT) and Fan (green) are working. I tested it with a volt meter that I touched one end to the green wire at a terminal board and the second wire to the ground.

The green wire connects to a terminal board and changes to an orange wire. The orange wire goes to a combustion relay (white box). I am not able to see the wording on the side of the white box (need mirror to see info) . Lots of orange wires going everywhere.

I do see a black wire and an orange wire going to the fan relay (black box) from the combustion relay. Then a red and blue wire meet up with the black hot wire going to the fan. I think the red and blue are for multiple speed blower motor.

I used the volt meter to test each step of the way.
1) other side of terminal board - works
2) no way to test on combustion relay, all wires are covered
3) fan relay - orange wire - yes
4) fan relay - black wire - no, I think this path is used when burning gas
5) fan relay - red to blower - no
6) fan relay - blue to blower - no

So, my opinion is the fan relay is bad.

What do you think?

Here is information on the side of the fan relay:
184-20114-406C
12FLA 60LRA 125VAC
8FLA 48LRA 250VAC
18A 277VAC
COIL 24V 50/60HZ
B12173
PAT NO 3,825,865

As a side note, I replaced my blower motor in February and asked for a replacement from the local parts store. The replacement motor turned out to be a multiple speed blower motor and I only connected the high speed (black wire). A couple of questions (By the way, I will not be attempting any this until after my current issue is resolved):
1) Is worth trying to leverage the multiple speeds available to the blower motor or is the bad idea?
2) When would the slower speeds be used?
3) Would the slower speed be used when running the fan in on position and change to full speed when blower is used for heating or cooling?

Thanks for all the help.

Brian

So, my opinion is the fan relay is bad.

What do you think?

Here is information on the side of the fan relay:
184-20114-406C
12FLA 60LRA 125VAC
8FLA 48LRA 250VAC
18A 277VAC
COIL 24V 50/60HZ
B12173
PAT NO 3,825,865


That is a very common relay that costs less than $10. So it is a cheap and easy replace if you are certain, but I would continue to diagnose as I am suspicious.

Didn't you say the fan works in emergency heat? If so, you have a fortunate case where you can check the inputs to that relay and the outputs. The input should be 24VAC and output just closes a switch. 24VAC terminals are on one end with switched 125/205VAC on the other. Back-probe (ie get your voltmeter probes in there somewhere), or disconnect and check, or whatever you have to check the input. On the output just check continuity. I would first check with the system is in emergency heat and then fan only. Please be careful as you are now near 110VAC.

Did you check across the green and common/neutral at the furnace board?

I am leaning toward your furnace board since the system works in emergency heat but not in fan only mode. But that's just a guess since there could be other relays or things in series.

You are on the right track. You are getting closer. Check your furnace wiring diagram. Post if you can along with any pics.

Did I mention be careful.


As a side note, I replaced my blower motor in February and asked for a replacement from the local parts store. The replacement motor turned out to be a multiple speed blower motor and I only connected the high speed (black wire). A couple of questions (By the way, I will not be attempting any this until after my current issue is resolved):
1) Is worth trying to leverage the multiple speeds available to the blower motor or is the bad idea?
2) When would the slower speeds be used?
3) Would the slower speed be used when running the fan in on position and change to full speed when blower is used for heating or cooling?


Black = high speed
Blue = medium speed
Red = low speed

I could have blue and red backwards as I am just on my first cup of Joe :coffee:, but check the motor diagram as it probably says.

You are safe by using high speed for both heat and cool. Mostly high is used for cool and sometimes you see medium used for heat.

Each speed has a different RPM and different static pressure that might work better or works for your ductwork, A/C & heat pump coil, heat exchanger and personal noise preference. There is no way I can say what is best for you, but the factory usually plays it safe and uses high.

But beware the risk of using a lower speed could overheat your heat exchanger, or freeze your A/C coil. :eek: I would say unless you have an unacceptable noise issue I would leave as is. Noise issues can also be delt with ductwork remediation.

It is possible your furnace board is smart enough to engage the fan-only at a different speed. There is no way of knowing without researching and testing a little bit. There are ways around it with a few relays and a diagram I can post if interested, but lets get the system working first.

I was trying to get our really old scanner that has been sitting in the corner of basement to work on the new computers - no luck.

Here is an image of most the wiring diagram. I can provide the far left side in another image if necessary. FreeImageHosting.net Hosting Service (http://www.freeimagehosting.net/image.php?3dc8e51e7d.jpg)

I started testing at the TERMINAL BOARD in the middle of the diagram. Then the wire (OR-28) goes to the combustion relay 7. I see it go through switch 8 and gooes to OR-28 to fan relay. I see the signal at 1 as it enters fan relay, but I don't see a signal at 3 (where I expected). I also tested voltage on 2,4,5, and 6.

So, let me know if should replace the fan relay or if I should start testing somewhere else.

To answer a couple of your questions,
1) Question: Which ground did I use to test voltage?
Answer: I tested with a common ground, not at the furnace board. Actually, as I traced the wires, I never made it to the furnace board, so I did not test a signal there. I figured the common ground was correct because it worked at the Terminal Board and at the beginning of the fan relay.

I am not quite sure what is the furnace board is. Is this the ignition controller?

The ignition controller is a RobertShaw HS780-NR308.

2) Question: Does the fan ever work?
Answer: The fan does work with emergency heat. We originally only had gas heat and air conditioning. When air conditioner went out, we spent the extra money to give us two sources of heat. My assumption is the gas heat uses the combustion relay to turn the blower on through a different path (ie: it never uses connection 1 on the fan relay). Actually, I am not quite sure what path is used by the air conditioner/heat pump/fan on to tell the blower motor to start working.

3) Testing the fan relay for continuity. When testing this, I disconnected all other wires from it.
a) test from 1 to 3 - no
b) test from 2 to 4 - no
c) test from 5 to 6 - yes

Thanks

Brian

I'm still digesting this diagram, but you may be right about the fan relay. I would however like to see the left hand side of the diagram. Can you post?

On the fan relay here is what I'm seeing:
1 - Power or 24VAC+
3 - Common/neutral
5 & 6 always tied together to pass through
4 & 2 connected when 24VAC+ power applied to terminal 1
The *HEATING BLOWER SPEED RD-18 is not controlled by that relays as it passed thru 5 & 6, but **COOLING BLOWER SPEED is by going thru 4 & 2. Cooling blower speed is used when running heat pumps whether in heating or cooling mode.

So...try this:
1. Disconnect terminals at 4 & 2
2. Turn on fan at tstat
3. Check for 24VAC at 1 & 2. You should get 24VAC power to that relay.
4. Check continuity at 4 & 2

Let me know what that yields.

Also, I am really interested in the inputs to the TERMINAL BOARD (center of diagram) with R, C, W, and G terminals. R and C are power and common/neutral headed to your tstat. W is power (24VAC+) coming back from tstat when tstat calls for heat. G is power for fan coming back from tstat when tstat calls for fan. So with tstat flipped to EM heat check these R and C for 24VAC, W and C for 24VAC, and G and C for 24VAC. You may have to bump the tstat up to like 88°F to kick on the furnace. Next, after you reset your temp to shutdown the furnace, flip on fan only from the tstat and take the same readings on those terminals. Finally, flip off fan, turn on A/C until you're sure the tstat is calling for cool and check those terminals.

Let me know what you find.

If you don't already know the Door Switch must be pressed to check for power at things (I think you know that).

I will continue to study the diagram and post a follow up if I think of anything else.

I bought the fan relay today and replaced it during lunch.

It works.

Thank you for helping me troubleshoot.

Brian

I bought the fan relay today and replaced it during lunch.

It works.

Thank you for helping me troubleshoot.

Brian

Glad to hear it worked :thumbup: Your instincts were right.

I guess you could have just replaced the relay and ignored my suspicions. Bet that relay was a lot cheaper than a $service$ call.