Installed a new Honeywell Programmable Thermostat RTH7500 for heat pump energy savings. Replaced an old York thermostat "York T874R 1046" with a Honeywell subbase Q674L 1272. After the installed the system worked well with the new thermostat for a few days. Then, I noticed the fan would not shutoff. The fan runs with all settings: System on/off, termostat on/off, and when thermostat is removed from subbase. All connections are solid and no wires are touching.

My York Air Handler has emergency electrical heat and located in the attic. I do not have an electrical schematic for the unit and a drawing is not mounted inside of the door panel. I think the Air Handler Model is 2HL06501506C (maybe the Coil Model number). Inspected the wiring from the thermostat: all connected, none touching, no visiable problems.

Im not very AC knowledgeable but not a novice and very comfortable working on the unit and its circuits.

Any ideas of the cause and test that I can perform.

Update:
Thermostat: York/Honeywell T874R1046, sub-base Q674L 1272
Furnace: York Electric.
Air handling section: N2AHD14A06
Heater section: 2HL06501506C

Where can I find an Electrical Diagram for the York Air Handler unit?

Look on the inside of the blower door.

Where is the relay or sequencer?

Here's a picture of my wiring inside the furnice:
http://i266.photobucket.com/albums/ii273/ScottyPyt/Heating-%20AC%20-%20Heat%20Pump/DSC04314.jpg

Here's the inside of the cabinet pictures:
http://i266.photobucket.com/albums/ii273/ScottyPyt/Heating-%20AC%20-%20Heat%20Pump/DSC04316.jpg
http://i266.photobucket.com/albums/ii273/ScottyPyt/Heating-%20AC%20-%20Heat%20Pump/DSC04317.jpg
http://i266.photobucket.com/albums/ii273/ScottyPyt/Heating-%20AC%20-%20Heat%20Pump/DSC04318.jpg
http://i266.photobucket.com/albums/ii273/ScottyPyt/Heating-%20AC%20-%20Heat%20Pump/DSC04319.jpg


Where is the relay or sequencer?

Thanks, I found the diagram inside of the circuit cabinet door.

I just need a little help here please...
Where is the relay & sequencer?
How do you test them?

Second pic sequencer is on right side. Test to see if M1 and M2 are closed. IE remove power and wires and test across terminals. (REMEMBER WHERE THE WIRES WERE)If they are closed then the sequencer is calling for the motor to be on at all times and it is defective. OR easier test is to just remove wires off M1 (TAPE THEM TO PREVENT SHORT)and energize the unit. If the motor has stopped running the sequencer is locked on and is defective.

Thanks for a response hvac1000.

In the second picture, how many sequencers are present? Only one has the M1 & M2 stamp.

Also in the second picture on bottom left, is a white box. It has what appears to be a switch on the other side. The switch is frozen on one side and will not toggle/reset. What is it?

Thanks for a response hvac1000.

In the second picture, how many sequencers are present? Only one has the M1 & M2 stamp.

Also in the second picture on bottom left, is a white box. It has what appears to be a switch on the other side. The switch is frozen on one side and will not toggle/reset. What is it?

There are 2 sequencers in that picture. Usually those control the electric resistance heat. There usually is another relay somewhere that controls the fan. Your picture is fuzzy, but I wonder if that bakelite brown piece to the left of the sequencers isn't the relay you want. Trace the wiring back from the fan and see if it goes to that piece. If it is, just pull the fan wire off the terminal, turn the power back on (you did kill the juice first, right?) and see if your fan isn't off. If it is, you found your relay. Next reconnect that terminal and pull one of the relay coil leads off. If your fan is still on then replace the relay. Unless something else is in parallel with it, like an overheat limit switch or the like, then you have to isolate the problem to the particular part. You have to use the schematic if you really want to troubleshoot things.

That white box looks to me (again fuzzy) like a circuit breaker. Those toggles don't move unless they are tripped.

EPM

M1=motor one
M2=motor two.

Underwriters Laboratories requires a

fan interlock circuit to insure the blower
remains operating whenever more than one
sequencer is used. The fan interlock should
be the M contacts of the second or third sequencer.






All M contacts are wired to the blower motor


so that any sequencer that is energized at will operate blower






http://www.white-rodgers.com/wrdhom/pdfs/instruction_sheets/0037-4799.pdf


http://www.white-rodgers.com/wrdhom/pdfs/06_Cat_pages/Cat_06_pg0096.pdf


Some units have relays and some just use the sequencers

OR easier test is to just remove wires off M1 (TAPE THEM TO PREVENT SHORT)and energize the unit. If the motor has stopped running the sequencer is locked on and is defective.

Did the Easier Test. Removed & taped both wires off M1 and turned on the unit.
Results: Fan came on...



Your picture is fuzzy, but I wonder if that bakelite brown piece to the left of the sequencers isn't the relay you want. Trace the wiring back from the fan and see if it goes to that piece. If it is, just pull the fan wire off the terminal, turn the power back on (you did kill the juice first, right?) and see if your fan isn't off.

The bakelite brown piece is a relay. I traced a wire back to the fan and disconnected it...
Results: Fan came on...


If it is, you found your relay. Next reconnect that terminal and pull one of the relay coil leads off. If your fan is still on then replace the relay. Unless something else is in parallel with it, like an overheat limit switch or the like, then you have to isolate the problem to the particular part. You have to use the schematic if you really want to troubleshoot things.

Pulled one of the relay coil leads..
Results: No fans but constant hummmm...

Tested for 24volts on the green wire from thermostat with power on/fan running. Nothing...

<snip>
The bakelite brown piece is a relay. I traced a wire back to the fan and disconnected it...
Results: Fan came on....
Pulled one of the relay coil leads..
Results: No fans but constant hummmm...

Tested for 24volts on the green wire from thermostat with power on/fan running. Nothing...

I'll admit, troubleshooting by email is a lot harder than hands on.

When you pulled the fan relay coil lead possibly you heard a hum that is always there, just masked by the fan noise. If the fan quit when that lead was pulled, something is energizing the fan relay. I don't know how you tested for 24 volts, but measuring from green to red at the tstat would show 0vac when the fan is being called. That's equivalent to measuring from hot to hot. Green to the C terminal should be 24vac with the fan being called. It appears by your pictures that you do not have an integrated control board so you should be able to trace where that signal is coming from. Turn the tsat so that it is NOT calling for cool (or heat), turn the fan switch to auto, wait for two minutes or so (fan overrun time SHOULD be finished) and then, if the fan is still running, check for voltage between red and green at the tstat. If you still have nothing (0vac) then something is likely wrong with the tstat. Disconnect the green at the tstat, if fan stays running then something is wrong in the wiring.

I REALLY need that schematic.

EPM

Here's the Schematic:
http://i266.photobucket.com/albums/ii273/ScottyPyt/Heating-%20AC%20-%20Heat%20Pump/Diagram.jpg

I'll admit, troubleshooting by email is a lot harder than hands on.

When you pulled the fan relay coil lead possibly you heard a hum that is always there, just masked by the fan noise. If the fan quit when that lead was pulled, something is energizing the fan relay. I don't know how you tested for 24 volts, but measuring from green to red at the tstat would show 0vac when the fan is being called. That's equivalent to measuring from hot to hot. Green to the C terminal should be 24vac with the fan being called. It appears by your pictures that you do not have an integrated control board so you should be able to trace where that signal is coming from. Turn the tsat so that it is NOT calling for cool (or heat), turn the fan switch to auto, wait for two minutes or so (fan overrun time SHOULD be finished) and then, if the fan is still running, check for voltage between red and green at the tstat. If you still have nothing (0vac) then something is likely wrong with the tstat. Disconnect the green at the tstat, if fan stays running then something is wrong in the wiring.

I REALLY need that schematic.

EPM
Agreed... Hands on is a lot better.. But now, I only have a humm... :(
Fan has stopped running.. :mad:

Tested for 24 volts from Green to C and thermostat turned off (fan auto). Result 0 volts
Maybe the relay completely died when testing... Hopefully... :confused:

With your stat off, FAN set on Auto you won't have voltage from G (Fan) to C (Common). Set the Fan to ON and you SHOULD have 24 volts.

Agreed.. The problem is that I have a fan running continuously with 0 volts on Green (fan) wire... And I don't want it to stay on with the AUTO setting... It SHOULD go off with heat/ac quits..

Look at 2R (Relay for blower motor) on your wiring diagram (lower right side). If this relay is defective (shorted closed) it will keep the blower running all the time no mater what you disconnect except the main power. Check 2R I have a feeling your problem might be located there.

Some times these relays can stick. You may be able to tap on it to free it up.

Tapping on the Relay didn't work.. I think it made it worse.. :(
I went from fan ON always to humming always... :mad:

Tried to find a replacement blower relay today and can't find one locally. The York (024-24984-000) relay is a 5-pin relay and all of the stores has 6-pin relays. Im being told that it's a (special order only) York part. Im searching online for alternatives..

Relay Manufactured by: ESSEX
Essex Part number: 134-20103-301Q
York Part number: 024-24984-000
12FLA 60LRA 125VAC
8FLA 48LRA 250VAC
18A 277VAC
COIL 24V 50/60Hz

Anyone knows of an equivalent relay that I can use?
What's a good online site for HVAC parts?

That is just a single pole single throw/single pole normally open relay. Known as SPST/SPNO relay with a 24 volt coil.

SEE actual page 115 on below info and tell me if it looks something like the relay pictured.

http://www.white-rodgers.com/wrdhom/pdfs/06_Cat_pages/2006_cat_sections/transformers_relays.pdf

If so you will need a 90-370 5 tab unless York had it modified for there usage. BTW you can use a 5 or 6 tab relay. Just follow the wiring diagrams listed on the Whire Rodgers relay page. You just have to used the same numbers for the connections you need. QUESTION?? Is this relay on a circuit board or freestanding?

Do not worry about the last 000 in the York part number. This site has it but it is expensive there.

http://bestbuyheatingandairconditioning.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=REL24249847&Category_Code=r-rbm


Cheaper here at Grainger

http://www.grainger.com/Grainger/wwg/productIndex.shtml?from=Search&newSrch=yes&operator=keywordSearch&search_type=keyword&action=Go%21&QueryString=90-370&submit.x=19&submit.y=1

ALSO I would suggest you look on the side of the relay for a wiring diagram and make sure you get the correct one. It will make life easier for you as far as wiring goes. Grainger stocks all these type of relays.

Here is the list page

http://www.grainger.com/Grainger/wwg/viewCatalogPDF.shtml?browserCompatable=true&adobeCompatable=true&toolbar=true&CatPage=3827

The really at bestbuy Heating & Air Conditioning is the exact match to my relay.
I do not have a circuit board and the blower relay is freestanding.
Its just to the left of the sequencers in the 2nd picture.

Relay wiring diagram:
- Pins 1 & 3 coil
- Pins 4-to-5 in default state
- Pins 4-to-2 in the activated/triggered state

Thanks for the info hvac1000! :)

My relay is:
1~~3 Coil
2... 5
.\
... 4

How would the 6 pin relay wire up?
1~~3 same as old relay wiring
5___6 same as old 5; 6 not used
2___4 same as old 2 & 4

Diagrams are different for triggering.. between my 5pin & 6 pin (http://www.grainger.com/itemdetail_largepic.html?item=XL-1N185.JPG)

Glad to help

Purchased the relay at Grangers today..
Now, how do I make the connections?

My old Relay is Normally Closed on pins 4 & 5
The new 6 pin relay Normally Closed is pins 5 & 6 and Normally open on pins 2 & 4.

http://i266.photobucket.com/albums/ii273/ScottyPyt/Heating-%20AC%20-%20Heat%20Pump/DSC04332.jpg


How do I wire pins 2, 4 & 5 from the old relay?

Looks like 5 and 4 are normally closed according to your wiring diagram then 4 and 2 activate upon 24 volt power.

Try putting a jumper between 4 and 5 also attaching the original wires to the respective terminals. Then attach the number 2 wire to the number 2 terminal.

Here is what should happen. When the new relay is not activated tabs 4 and 5 will be together just like the old relay. When 24 volt power is applied terminals 2 and 4 will be activated droping terminal 5 out.
You might test this using 24 volts to activate and unactivate the relay and your meter to make sure I am correct.

NOTE no changes necessary for the 24 volt feed/activation wires. Just use the same numbers.

I have 5 wires..
So should I wire as follows:
#1 wire to #1 terminal
#3 wire to #3 terminal
#4 wire to #4 terminal
#5 wire to #5 terminal
#2 wire to #2 terminal
Jumper between 4 & 5 terminals

I would have thought to jumper terminals 4 & 6 to complete the circuit for normally closed...

You can jump between 4 and 5 or 4 and 6. They are actually the same terminal since they are jumped internally as long as the relay is not energized with 24 volts.

I stated terminal 5 so as not to confuse the issue by adding another terminal number.

Cool..
Installed the new relay.. just get a humm from the fan..

Will investigate tomorrow.. and post results.

On thing you might do is to jump or remove the relay from the equation then see if the blower motor runs.

What wires do I jump? Coil wires?

NO do not jump the coil wires those are 24 volt and it will burn something out since that will cause a direct short in the low volt system.

Disconnect wire on tab 5 or 6 depending upon which tab you used (see other discussion on this) then Jump 4 and 2 and see what happens. This way you are making direct contact for voltage to the motor and the motor should run.

Put wires back where they were
Then
Then try disconnecting 2 and jumper 4 and 5 and see what happens


NOTE: this is the W/R page for this relay..


http://www.white-rodgers.com/wrdhom/pdfs/06_Cat_pages/Cat_06_pg0115.pdf
I hope during this entire process you have identified all the wires that are being used on this relay. If they get mixed up you will have to trace back and that will take all the fun out of it.

Thanks for the info. Will test it later today.

Wires are labeled by number...

Okay guys.. Im back home. Had to go out of town for a short trip..

Here's the test results from Saturday:

Installed the new relay and wired per instructions. All I get is a constant hum from the fan with thermostat is in off position.

Jumpered relay wires 2 & 4 to test the fan. The fan comes on.

So, I reinstalled old relay. It gives me the same results. Now, my fan only comes on with jumpered wires 2 & 4.

What changed?
Don't make any sense as I haven't changed anything else..
What should I test next?

If 2 and 4 when jumpered works the fan then something is wrong with this picture.

When the unit is in the A/C mode check for 24 volts on pin 1 and 3. There should be 24 volts there and the relay should pull in to activate the fan.

If 24 volts is not present then another device is holding the 24 volts from getting to the relay.

The only other possibility is that we have the relay wired backwards but I really do not think so.

If 2 and 4 when jumpered works the fan then something is wrong with this picture.

When the unit is in the A/C mode check for 24 volts on pin 1 and 3. There should be 24 volts there and the relay should pull in to activate the fan.

If 24 volts is not present then another device is holding the 24 volts from getting to the relay.

The only other possibility is that we have the relay wired backwards but I really do not think so.

Hey HVAC.. Thanks for the response..

Agreed, something is wrong with this picture... First, I have always on fan. Now I have a always hum and instead of the fan on...

But before I go up in the attic to check for 24v on pins 1 & 3, I just completed a little test that sort of did the same thing... I changed the fan setting on thermostat from auto to ON always. Turn on power at air handler and the fan came on..

But I like your test better... I post again in 30 min..

Maybe I'm doing something wrong, but I don't get 24v on 1 & 3. I put the positive DVM on terminal 1 and negative DVM on ground = 0. Same on #3 terminal.

Did I do this correctly?

Set the volt meter for the scale that will read the 24 volt circuit.

Then disconnect both wires from the relay.
Then attach the meter to the two wires and see if you have 24 volts when the system is in the A/C mode. If not try the fan on mode on the thermostat and test again. I never trust the frame ground for testing. Test using the wires only. They must be disconnected from the relay for the test.

If you do not have 24 volts there you are going to have to trace back to find the 24 volts and the reason it is not getting to the relay.

Will do.. Back to the attic I will go..

My DVM has Vac, Vdc, Aac, Adc, Ohm, F, & uFarads.
Ive been using Vac.

Attached to the removed two wires; 1 & 3.
In A/C mode = 0
In Fan On = 26.2

The relay should be activated in the A/C mode.

See below

http://customer.honeywell.com/techlit/pdf/69-0000s/69-0392.pdf

See section 5
When C1 makes it triggers the fan relay through the on off fan switch in the off position.

Now I am starting to believe there could be a problem with the wiring at the thermostat. Why it worked for a few days is anyone's guess.

Okay..
Last night, I noticed that the new relay was melting at terminal #3. The plastic started to deform.

So, I put back the original relay and tested the heat cycle (as it was cool last night here). Everything worked fine except for the hum when fan was off. The fan went off during the system off stages and the fan came on with the heat pump during the heating stage. Everything works as programmed.

Changed the Thermostat to AC this morning and the old symptoms returned: Fan hum always and the Heat Pump/fan goes on & off as called by the thermostat. Then I set the Thermostat to OFF but the fan continues to hum.. This is strange.
Killed the power and came to work.. :(

Im now thinking that it is the Thermostat wiring too. The new relay wiring is also suspect but Im ordering a new original York relay just to be safe. Also still wondering about the high transformer reading.

Thermostat wiring connections:


Old = New
R = R and Rc Jumpered
Y = Y
G = G
O = O/B
W = Aux
B = C
X = E

.

#3 should not be melting. Having 26 volts instead of 24 volts is normal and OK.

Yep #1 & 3 must have overheated or something. They both started to melt down.. That's why I suspect the relay wiring..
Actually Terminal #1 is much worse than #3..

http://i266.photobucket.com/albums/ii273/ScottyPyt/Heating-%20AC%20-%20Heat%20Pump/DSC04350.jpg

Ok

Well do my thermostat wiring look correct?

I got the wiring directly from Honeywell ECC Customer Care..


Old = New
R = R and Rc Jumpered
Y = Y
G = G
O = O/B
W = Aux
B = C
X = E
.

I checked the old subbase on Honeywells site and then the new one. I believe it is wired correctly but I am not there to test it. What bothers me is the fact that the low voltage relay has signs of overload at the low voltage area. That is strange.

What should I do next?

Just wait and install the new York Relay tomorrow.

Low voltage overload? What should I test to find it?

Im concerned about the humming when the fan is off. Its like the unit is sending power to something that is shorted... Sounds just like a blown/blocked electrical motor; bone stuck in a kitchen sink disposer. Yeah... Like something is stuck!

Exactly where is the hum comming from? Low voltage transformers are a known to hum but that kind of hum is OK. It is just loose laminate plates in the transformer.

Correction: The sound IS coming from the transformer.
How can I fix the loose laminate plates inside? Or does it require replacement?

I will pickup the replacement York relay today.

Installed the new relay..
Starting the AC & heating testing while viewing fan functions.

If the crimp terminals at the end of the wires are not crimped solidly, or they don't grip the terminal VERY tightly, you can get heat damage that can show up like you see on that picture of the fan relay you posted yesterday. I'm not sure that I've ever seen it on the low voltage section of a relay like that, but check them. If they aren't gripping the terminal tight enough, just pinch them a bit with a pliers. Don't go overboard though or you won't get them back on.

Usually a loose connection like that will show up with a bit of tracing with your DVM. You have to measure THROUGH the connection, so check the resistance of the relay coil and subtract it from the reading from the far end of one of those wires through the relay coil to the other terminal. You should get 1 ohm or less if the terminal and crimp are OK.

Don't worry about the buzzing low voltage transformer unless it is LOUD or very hot. If you really don't like it, replace it, but I've had new ones that hummed. Usually cheap no-names, but I've had it happen with major labeled ones too. I just changed a leaking gas water heater today that has been humming for a long time.

Thanks EP..
I checked the crimp terminals. They looked good but I tighten them a little and reinstalled them. The resistance difference was 0.02 ohm after tightening.

Hey guys,
After my initial test, It appears the Fan relay was the problem.
Tested all of the thermostat functions: AC ON, Heat ON, and Everything OFF.
Fan is working as normal again.. Guess that you can only use York Relays...
I will monitor over the next few days. Hopefully, everything will work correctly. :)
Thanks HVAC & EP for your assistance through this. :D

Now, how can I fix the loose tranformer laminate plates?
Or does it also require replacement?

.

Thanks EP..
<snip>Now, how can I fix the loose tranformer laminate plates?
Or does it also require replacement?

I don't know of any way to fix that. The magnetic flux in there will defeat any bending and crimping that you can do. You will have to replace it if you don't like it. See my above post.

EPM

The only thing I can figure is the first relay you got was defective since the terminals work out to be the same. The best thing is you got it running and that is all that counts.

Hello Scotty,
I'm Jimmy the air guy I have 25 years in the business and I'm here to help.
My hats off to you for buying a new heat pump.
That's a very wise thing to do.
Relax because the problem you're most likely experiencing
Is a minor one.
It is most likely a stuck sequensor.
The sequensor is a part that is in your fan circuit,its purpose is to run the fan for 60 to 90 seconds after your unit satisfies the thermastat.
To verify this simply tap on the sequensor after the units thermastat stops calling and see if the unit stops.( that usually frees them) if not simply replace the part. They normally run about 25.00 if you can pick one up at a supply house.
Good Luck and GOD bless.

Hi JimmyTheAirGuy. Great suggestion but you are a bit late on that one. The sequencer situation was covered in the beginning of this thread and was tested by Scotty. Stuck or defective sequencers are a common problem with electric furnaces as you are well aware of.

It is great we have a new person on board that has HVAC knowledge but please try to read all the posts on a thread to see if any ideas you have might have already been covered. This helps to make things a bit easier for the person doing the repair. Once again glad to have you and your knowledge on the board. We have a great group of folks here who try there best to help people.

Thanks HVAC..
Jimmy, thanks for the info.. I just might replace the sequencers if the problem returns (16+ yrs old parts). But, I have 2 different kinds: Seq-one with 3 levels of connections and Seq-two with a single level of connections. Also been researching doing a conversion of my air handler blower control from a single speed to multiple speed for Heat & AC. I can incorporate new sequencers as part of the project.

But currently after 2 days of monitoring, my unit is working as normal without problems.

ScottyP,
Glad to hear all is well with your system. Hopefully your system will last for years to come.
Remember, your systems performance will only be as well as you allow it to be.
With today's energy concern these systems are built a bit more sophisticated then they use to be with extra limits and lockouts. Some good advice would be a solid preventive maintenance plan. For the do-it-yourselfer you can contact your manufactures web site and download a free manual for maintenance suggestions or visit my website at ]http://jimmytheairman.com/tipsfromjimmy.aspx[/URL].aspx also free of charge.
For the consumer you can contact your areas chamber of commerce and get a list of reputable hvac contractors. Please keep in mind that the most important investment you can make on your home or office is the comfort of it. So, cheaper is not always better.

Jimmy The Air Guy