Heat pump defrost board wiring question...

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Old 01-18-15, 09:05 AM
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Heat pump defrost board wiring question...

My family's heat pump stopped working sometime overnight. When I went outside to have a look at the wiring box on the side of the heat pump outside, 3 lizards (anoles) tumbled out, 2 were still fighting. Apparently they had been fighting in there. I can't find any damage to anything indoors, at the thermostat, or outside in the heat pump unit...but it still won't do anything when the system is turned on at the switch indoors. After dusting around inside the wiring box on the exterior heat pump where the lizards were, I found what I HOPE is the culprit: an un-coupled wire coming from a board (more of a microboard, really). The only problem is that there are 3 possible prongs it could have come off of, and I'm worried that trial and error could cause electrical damage to the unit.

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It's either one of the 2 prongs behind the red wire, or next to the connected yellow wire at the bottom of the dark brown unit in the center of the photo. I can't imagine these things have wires that are supposed to be connected to nothing at all.

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Edit: The board the wire originates from is labeled "Defrost control", and the wire is from a connection labeled "Out". On the schematics (which show the order of the Defrost Control board's connections in reverse compared to what's in there now) it looks like this wire's supposed to be connected to the left side (either the top or bottom prong), but I can't tell which of that brown unit.
 

Last edited by PJmax; 01-18-15 at 10:27 AM. Reason: enhanced pictures
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Old 01-18-15, 09:28 AM
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Welcome to the forum! To better assist please post the model number of your outside unit so a wiring diagram can be accessed to help determine where the wire should go. There is a great possibility the 3 or 5 amp automotive style fuse inside the air handler blew.

Can you follow the loose wire to see where it leads?
 
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Old 01-18-15, 09:51 AM
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I've found dead spiders, ants, lizards, rats, - you name it - inside outdoor units. They can eat wires causing a short or non-function. Or die and the decaying body destroys a circuit board contact or relay.

A picture of the outside unit and a pic of the control panel would help. Also brand, model, and serial numbers of the unit.
 
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Old 01-18-15, 10:19 AM
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I enhanced your first picture and added the blue line to your second one. We know where the wire connects to but it's hard to tell what the relay is in your picture and its orientation.
 
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Old 01-18-15, 10:33 AM
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Nice enhance, PJ!

We need a head-on shot of the control panel to see what wire lead he's holding.
 
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Old 01-18-15, 11:30 AM
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Now the unit seems to be working properly (powered on and off and run until the house reached the desired temp, then shut off normally 3 times since I posted last), but I STILL haven't connected this wire. What the...anyway, the indoor unit is a Heil, and there's no identifying brand on the heat pump aside from "Super High Efficiency 7000" across the top of the fan housing. On some parts there's a faded label with voltages that read "Inter-City Products". This thing was installed into a remodeled duplex that was converted into a single home my family moved into in 1992.

Here's the board



And here's a zoom-out

 
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Old 01-18-15, 01:18 PM
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I would connect it to the spot where the white arrow is pointing. The first photo is of your unit. The other photo is of a similar unit to yours.
 
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Old 01-18-15, 03:21 PM
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That looks just right! Thank you!!
 
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Old 01-18-15, 04:37 PM
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You are welcome. Post back and give us an update if all is well.
 
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Old 01-20-15, 04:31 AM
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I've been trying to respond to this page for a day now, and getting a "Page not found error". Weird. Anyway, the outdoor fan started working before I connected the loose wire Sunday, and everything was running fine all through Monday. This morning, the fan isn't working again. I don't have time to open the panel before I head to work (I have to also unscrew and remove the fan from the top of the unit to do so), but I'll get back on this when I get home tonight.


Edit: Now it's running again. Either this thing's showing it's age...or it's showing it's other-3-letter-word-that-starts-with-an-A. This isn't like the times we've had it repaired previously. Those times, the fan would hum when it wasn't working. This time it's absolutely silent. I wish our old repair guy was still around. He was a friend of my dad, so...well, freebie repairs with a monetary tip, until he moved to North Carolina.
 

Last edited by Rhio2k; 01-20-15 at 04:48 AM.
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Old 01-20-15, 08:12 AM
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The fan shuts off while unit is in defrost mode. Is it possible it may have been in defrost mode when you saw the fan was not running? It may only have an issue when going into defrost.

If that is not the issue, my next step would be to check the run capacitor and relays. Here is a service manual for Heil heat pumps manufactured in the 1990's that contains wiring diagrams and troubleshooting guides that may assist:

http://icpindexing.toddsit.com/docum...2808100101.pdf
 
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