Heat Pumps and Electric Heating - Bryant-Carrier-Heat Pump- 5A fuse blowing constantly

Initially I had the 5 Amp fuse blown inside the indoor unit. I replaced it during the day time (indoor temperature was about 68 and the outdoor temparature was maybe 60), I set the thermostat to 70 and the heating worked fine during the day. Then again the temperature dropped that night outside to about 40 and the room temp was very cold in the morning and I checked the fuse in the indoor unit and it was blown again. Replaced another fuse and it worked fine during the day when it was about 55 - 60 outside. Then I decided to turn OFF the unit. Today early morning the outside temperature was about 45 and the indoor was about 67 and I turned ON the unit and I set the thermostat to about 70 and immediately it blew the fuse . I inspected the indoor unit wires (where the blower motor, transformer and 5A fuse are located) and the outdoor unit wires (where the contactor and defrost board are located) everything looked normal ( No bare wires or burnt wires or burnt components ).
Can someone point me in the right direction on this issue?

Thanks

Sounds like your fuse pops when you have a heat demand greater than 2 degrees. This would point to a short in your auxillary heat control. (W, W2. Aux wire) or sequencer. Remove power, isolate and ohm W to C and ground.

http://i151.photobucket.com/albums/s160/Houston204/HeatPump.jpg

http://i151.photobucket.com/albums/s160/Houston204/Sequencer3pole.jpg

Also ck outside unit for short , as in mainly wire from W2 to outside unit connection , any small black burn marks on door when you remove < been there B-4, even defrost sensor wire < been there 2

Thanks for your responses. This morning I replaced the 5A fuse and set the thermostat to 71(Emergency Heat) , room temp. was 68, Outside temp was around 45. Worked fine on Emergency heat without a problem. The problem seems to be happening only when the thermostat is set to normal heat mode. Also I went to the outdoor unit and checked the door for any signs of burns. It was clean. Do I still need to measure the resistance between W2 and C ? Do I measure resistance at the indoor unit ?

Are Aux and E different wires at your stat?

As in this example...
http://i151.photobucket.com/albums/s160/Houston204/HoneywellQ674L1207.jpg

Try to check wiring behind t-stat and see if any wires are wat to close to another

Back to square one. This morning tried the emergency heat , set t-stat to 70 , room temp was 63, the fuse popped immediately. Also behind the t-stat, White wire goes into Aux and the E is empty. So now, At which point (Air Handler or Heat Pump or t-stat) do I measure the ohms for the W2 and C ? How do I test whether the sequencer is good ? I have a digital multimeter.
Thanks

Do you have any unused wires to your stat and outdoor unit?
If a short is suspected, switching from white to black or some other available wire at stat, heatpump and air handler would be quicker than tracing wires for a short. You would need to remove power to the heatpump and air handler first.

Do you have a digital camera? Pictures can be posted here using Image hosting, free photo sharing & video sharing at Photobucket (http://www.photobucket.com)
Posting some pics of your wiring at the heatpump and air handler may help. Someone on this site may spot a problem that you haven't.

I have two spare wires Black and Blue at the t-stat, Airhandler and Heatpump.

Here are the pictures of the Heat Pump and AirHandler Wiring:

HeatPump picture by ckadir - Photobucket (http://s636.photobucket.com/albums/uu85/ckadir/?action=view&current=IMG_1720.jpg)

AirHandler picture by ckadir - Photobucket (http://s636.photobucket.com/albums/uu85/ckadir/?action=view&current=IMG_1724.jpg)

Resistance Measurement between:
C and Aux -- 1294
C and G -- 820
C and Y -- 14
C and O/B -- 13
C and R -- 99

Resistance between C - Y and C - O/B are indicating short (At the thermostat wiring).

You must isolate the control wires at each end before this test. Be sure to write down where each wire was connected.

1. I opened the electrical connection door on the heat pump. Disconnected the the White connector marked P1 on the board( 5 control wires together ORW2YC) to isolate the Airhandler/ Thermostat side. Then checked the pins and found out that the short was present between any two of the three pins on the defrost board (O ,Y and C ).

2. Then there was another white connector with 4 wires ( Yellow-blue, Yellow-brown, Orange, Orange) going to the board marked P2 , TIC C O and I disconnected it from the board. Did the continuity test on P1 and there was no short any more.

3. Of the 4 wires on P2, two (Yellow-blue, Yellow-brown) were going to the Contactor and other two (Orange , Orange) were going inside the heat pump to some component near the compressor.

4. Now I disconnected the two wires going from P2 to contactor (Yellow-blue, Yellow-brown) and I was able to see a short between C and O on P1 .

5. Now I connected Yellow-blue into the contactor, still same as step 4

6. I removed Yellow-blue and I connected Yellow-brown same result as step 1

Questions :

1. Is the Contactor a suspect ? if so, how do I test it ?

2. Is the orange and C supposed to be short ?

3. I have a tall Bryant heat pump (outdoor unit), I only able to see from the top of the cage. From the top I dont see any damage to the orange wires and also dont see it rubbing agains anything (copper tubes or anything). I dont know a safe way to open the cage to have an horizontal level access. If I can do this , I could do a closer inspection of the condition of the orange wires.

Here is the picture of my Heat Pump Wiring:
HeatPump picture by ckadir - Photobucket (http://s636.photobucket.com/albums/uu85/ckadir/?action=view&current=IMG_1720.jpg)

What is your heatpump model number? If it is a Carrier I can get the diagram from their website.

I doubt that the problem is your contactor or reversing valve (orange/orange) since this problem only happens with a high heating demand (unless this has changed).

Have you tested the field installed W wire to ground? (other side of the P1 harness) This is the wire that I suspect is our problem.

How many ohms did you measure across the contactor coil? 13 would seem low, but I will check this with a new contactor in the morning.

Did you isolate and measure those 2 pink temp sensor wires to ground?

My Outdoor unit is Bryant and the model#213RNA030-A. The indoor unit (Air-Handler) is labelled Carrier.

Clarification:
"Have you tested the field installed W wire to ground? (other side of the P1 harness) This is the wire that I suspect is our problem. "

Do you mean to remove the harness from the defrost board P1 location and measure resistance beween W and C through the harness holes?

"Did you isolate and measure those 2 pink temp sensor wires to ground? "

Do you mean to remove the 2 pink wire harness from the defrost board and measure resistance between the Chassis and the each one of the pink wires through the harness holes?

I will also measure the resistance between the coil contact points in the Contactor and get back.

Thanks

1. I checked the resistance for the Orange-Orange it was 15.4 Ohms. Contactor Coil resistance was 16.4 Ohms. Also with the outdoor control wires disconnected from the defrost board, I came back to thermostat and measured the following resistance
Resistance Measurement between:
C and Aux -- 1218
C and G -- 822
C and Y -- 0
C and O/B -- 0
C and R -- 0

2. It was my mistake on my earlier post, that I assumed that the low resistance to be short when my continuity test beeped on O ,Y and C pins on the defrost board.
3. I also checked the Pink-Pink wire connector on the defrost board, which I believe was the temperature sensor wires and there was no short.
4. I also removed the defrost board and found that the front and back was clean (No burnt marks or burnt components)
5. Since I did not find anything wrong on the outdoor unit, I decided to start from beginning from inside the home. Replaced another new 5A fuse in the Air-handler.

6. Tried turning ON just the FAN on the thermostat. After maybe 5 minutes of trouble free working. My room temp. was 78. I ran the Cooling to bring down to 72. With the FAN still in ON position instead of the regular AUTO. It worked fine.
7. Then set the thermostat to 75 to heat up and it worked fine. Then set thermostat to 77 on emergency heat , that worked fine too.
8. Then I turned OFF the heat pump (Whole System) on the thermostat and decided to run the FAN on ON position instead of AUTO all night. Maybe after 3 hours of running, the FAN stopped working, I went to Airhandler and found the fuse popped (this was my last spare fuse).

So, I believe there is something wrong in the Air-handler, maybe a bad component in the blower motor circuit.

Please let me know what you think could be the suspect based upon this situation.

Thanks.

0 ohms = dead short
OL = infinity or open circuit
I suspect that you measured OL (C-Y, C-O, C-R).

When you set the fan to ON for the night, was heat mode also enabled?

G (usually the green stat wire and gray air handler wire) is fan.

What does the circuit board in your air handler look like?

Does the stat wire appear cut where it enters the air handler?
Try pushing the brown stat wire further into you air handler.

http://i151.photobucket.com/albums/s160/Houston204/CarrierAHUshort.jpg

I am sorry, I meant Open Circuit on (C-Y, C-O, C-R). My meter was indicating the number 1 (for open Circuit).

Physically the circuit board looks fine in the Air-handler. I have a the picture of the board here:
http://s636.photobucket.com/albums/uu85/ckadir/?action=view&current=IMG_1722.jpg

I will inspect the wiring and circuit board again at air handler and get back.

On the thermostat, when I set the FAN to ON for the night, the Heat was not enabled. Just the FAN was running for testing everyting else was OFF on the t-stat.
Thanks

Go to the outdoor unit. Turn off power and look in through the fan guard, you should see wires to the reversing valve and (if installed) high and low pressure switches. If the wires are laying on any copper pipes and you see what looks like white powder, there is a short. Ontherwise if wires are on pipig open and inspect wiring.

At the AirHandler disconnected the thermostat side and also disconnected the outdoor unit by removing the control wire connector. Here at AirHandler jumped the wires G and R and ran the FAN over night and no problems.

So now,
With the Outside Condenser Unit disconnected ( I had removed the Control Wire connector from the defrost board to isolate the outdoor unit from the Air Handler)

1. I rewired to the original wiring at the Air Handler and also reinstated the thermostat. Now the only thing is the outdoor unit isolated.

2. I decided to run the FAN ON (Not AUTO) and heat pump SYSTEM OFF over night through the thermostat control. It worked fine.

3. Now with the FAN stable, I tried using the Emergency heat this morning to heat up the room temp from 67 to 72 and it worked fine.

4. Planning to try the emergency heat for a few more days to make sure the fuse is not blowing before focussing on the possible Outdoor unit issue.

At this stage, it looks like there might be a problem with the Outdoor Unit components or Wiring within the unit or the control wiring between Air-Handler and Outdoor Unit.

My outdoor heat pump unit is about 5 feet tall, I can open the top access cover that has the FAN attached to it. But how do I open the side cover to gain a closer access to inspect the condition of the wires ? Never done this , any help would be appreciated.

Does this link work? It's an exploded view of what I believe is your outdoor unit.
http://www.epic.hvacpartners.com/epic06/Part/ShowDrawingDetails.html?DrawingIndex=1&PartNumber=329640-701166&ModelCode=213RNA030000BAAA

This link does not work:
http://www.epic.hvacpartners.com/epi...3RNA030000BAAA

Didn't think so, Lennox will let you do it not Carrier/Bryant.

Click here: Jarredsdad Website (http://jarredsdad.embarqspace.com/#/welcome/4529420987)

Then click the button that says: 3RNA030000BAAA