no heat,no air, blower on contiuously Payne394J

[ridodami4]

I first replaced thermostat, nothing.

replaced control board , still nothing

whats next??  HELP!!!

[hvacdrd]

Start from scratch. Remove all the thermostat wiring at the control board including the wires going to the outdoor unit. Then turn on the power and tell us what happens.

If the blower continues to run then take a look at the limit circuit. Post a picture of the unit with the covers off if you are unsure where to look.

What was the part number of the control board you replaced?

[ridodami4]

I pulled all the wires, blower still on.

replaced board: HH84AA 011 with HH84AA020

don't know what the limit circuit is, was also told to check the fusible link??

[hvacdrd]

Nope, not on this one. Sounds like you may have blown a transformer. This board requires 24vac to open the circuit to the blower motor. If no 24vac then it runs continuous like you have described.

With your meter, power on at furnace, check from terminal 'R' to 'C' on the control board. If no 24vac, check the 3 amp fuse on the bottom right of the board. If the fuse is ok check for 24vac at SEC-1(Blue) to SEC-2(Red) on the upper right side of the board. If no 24vac here you'll need a new transformer.

I believe the 011 board did not have a fuse to protect the transformer like the 020 does.

...and the picture of the day goes to...

[ridodami4]

much thanks for the quick reply.

 

looks like the transformer...great job

 

Iowe you a cold one!!  Ridodami

 

[hvacdrd]

When you install the new transformer don't hook up the wires going to the A/C circuit (terminal Y & C) before checking the wires for shorts, maybe a cut line outside from grass trimmer or chewed wires. A stuck contactor will blow the fuse as well. Have an extra 3A fuse handy if you don't find anything. Let us know how you do.

[ridodami4]

I dont know whats up . Ive got 24 between SEC1 and 2. but not between c and r and my fuse is ok.

[dkpd1581]

Lets start back from the begining.

1.  With a pen and pad, write down what color t-stat wire is connected to each terminal at the bottom of the board - R C G W Y.

2.  Turn power off to the unit and then remove the t-stat wires completely from the board.

3.  Remove the car fuse from the board and check for continuity with your meter - not just by visual inspection.  Occasionally they will LOOK good, verify this beyond a doubt with the meter.

4.  Replace the fuse if good or install a fresh one if necessary.

5.  Remove SEC 1 and SEC 2 from the board and without allowing them to touch anything and verify that there is 24 VAC with power now applied to the unit.  If there is, reconnect them to the board.

6. With SEC 1 and SEC 2 reconnected to the board and power applied, check for 24 VAC between the now unwired R and C terminals.  If none, then the board is bad and needs to be replaced.

When you get this far you should know whether the t-former is good, the fuse is good, the board is good.  By removing the t-stat wires and checking the unit this way, we "half" the problem. 

If the t-former is bad or the fuse blown, there is a 24 VAC short somewhere in the system or a bad/stuck contactor.  After they (t-former, fuse) have been replaced and without the t-stat wires attached, they should still be good.  Therefore are problem is elsewhere.  We can start looking at the wiring, the t-stat, bad contactor, etc.. 

Start here and let us know, then we can go throught the possibilites from there.

[ridodami4]

Rechecked the fuse  it was ok.

then bypassed the limit circuit and blower turned off.

reconnected the limit and everything came back to life..am going to replace limit just in case.  It is located behind the black square at the top of my original attachment.

 

MYSTERY  SOLVED  thank you all for your advice...Rick

[Brew Man]

Hey,

That's where it's at.

[applianceman18007260692]

This kind of advice right here is outstanding ,I am glad I had a part in setting up this HVAC forum   Keep this up!!! this is the bomb!

[jmk1447]

Help!!! Reading in forum....I am having this exact same problem. I know the post is from 2007, but hoping to extract some help. I have a Carrier Furnace 58GS075-CA. The blower is running continuously. I ran your tests as outlined below; Based on my results I replaced my circuit board HH84AA 011 with HH84AA020, but the same problem still exists. I have voltage between SEC-1 and SEC-2 but not at R and C terminals. If I apply voltage at the R and C terminals the blower shuts off. Any advice on what I should do next?

1. With a pen and pad, write down what color t-stat wire is connected to each terminal at the bottom of the board - R C G W Y.

2. Turn power off to the unit and then remove the t-stat wires completely from the board.

3. Remove the car fuse from the board and check for continuity with your meter - not just by visual inspection. Occasionally they will LOOK good, verify this beyond a doubt with the meter.

4. Replace the fuse if good or install a fresh one if necessary.

5. Remove SEC 1 and SEC 2 from the board and without allowing them to touch anything and verify that there is 24 VAC with power now applied to the unit. If there is, reconnect them to the board.

6. With SEC 1 and SEC 2 reconnected to the board and power applied, check for 24 VAC between the now unwired R and C terminals. If none, then the board is bad and needs to be replaced.

When you get this far you should know whether the t-former is good, the fuse is good, the board is good. By removing the t-stat wires and checking the unit this way, we "half" the problem.

If the t-former is bad or the fuse blown, there is a 24 VAC short somewhere in the system or a bad/stuck contactor. After they (t-former, fuse) have been replaced and without the t-stat wires attached, they should still be good. Therefore are problem is elsewhere. We can start looking at the wiring, the t-stat, bad contactor, etc..

Start here and let us know, then we can go throught the possibilites from there.

[hvacdrd]

Check for an open limit (located right behind the gas valve on picture with this post). The limit will open a circuit from the transformer 24vac to the "R" terminal on the board. This also drops power to NC contacts for the blower. Check for dirty filter, air flow restrictions, etc

Also note in the future it is best to start a new post instead of tagging onto another.

Here is the piece of the diagram...

 

[jmk1447]

This was the solution!  Thanks for the help.  Wish I would have checked first.  I did end up replacing the circuit board, but at least did it for $50 (found one on ebay local).  Thanks so much for the help!

 

Joe

[applianceman18007260692]

outstanding