Friedrich dehumidifier repair

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Old 07-04-16, 08:22 PM
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Friedrich dehumidifier repair

Hello, I have a Friedrich D70D dehumidifier that slipped off a platform it was setup on in the basement, took a knock, and has stopped collecting water. The fan and all other functions seem to work fine but I don't hear the compressor kicking in. I took it apart and inspected it and there's no visual damage anywhere, no evidence of a punctured coil or anything like that. I've tested all the various switches (full bucket, etc) and cables and they seem fine. Based on my research on this site and elsewhere on the web, there's a good chance it could be the start capacitor and / or the relay switch. I'm fairly comfortable using a multi-meter but I'm not entirely sure how to go about isolating the problem. My meter is fairly basic, has a resistance setting but not a capacitance setting. I'm comfortable soldering and would love to get this thing running again, if only to keep it out of the landfill. Attached some pics below.

Many thanks for any suggestions!

Best
Eben

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Old 07-04-16, 10:23 PM
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Welcome to the forums.

You must have been reading here.... you posted useful pictures !

Here's the one we're going to start with.

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The blue is connected to the white and is the neutral.
The brown is 120v to the compressor relay.
The red is 120v from the relay to the compressor.

Temporarily remove the red and brown wires from the compressor relay and connect them together.
Plug the unit in. The compressor should start as soon as the unit is plugged in. Does it ?
 
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Old 07-05-16, 08:55 AM
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Hi, thanks for the quick reply!

The compressor kicks right in when I bypass the relay, sounds like it's running fine. So I suppose I need to replace that part, correct?

The exact part number (Song Chuan 855AWP-1A-C2) seems to be discontinued and replaced with an identical looking part with a different number . . . I suppose I can check the data sheets to make sure it's the right match.

All the best
Eben
 
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Old 07-05-16, 11:07 AM
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I doubt the relay is bad.
I'd resolder the relay to the board next.
Look closely at board and check for other solder issue/cracks.
Make sure all sensors are connected and have no broken wires.

Keep in mind that the compressor is delayed turn on.... up to five minutes after turning unit on.
 
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Old 07-18-16, 04:40 PM
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Hi,

I had to take a break from this caper but I'm back on the case now . . .

I've checked for continuity between all the various wires and solder joints, there's no sign of any damage or loose connections. The temperature sensor seems to be accurate, tested against a small digital humidity / temp meter. I had previously tested the humidity sensor by steaming up the shower and then placing the unit in there - I left it running at the most aggressive setting for a over 30min but the compressor never kicked on. Now that I have the whole thing disassembled, I tried steaming the humidity sensor with a kettle of water just off boil. The humidity display did finally respond with the steam wafting directly over the sensor, and after a minute or so the compressor kicked on. I removed the steam after another 20 seconds or so, and shortly after that the compressor cut out again. So, it seems the relay is fine and the sensor is likely the problem. My question now is, is it possible to bypass the sensor in some way to force the compressor to run, so that I can confirm that the refrigerant / coils are not leaking and the unit will actually put water in the bucket? If not, the sensor board is only $12 so I would take a punt on it.

Many thanks again for the help!
Eben

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Old 07-18-16, 08:11 PM
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That's a combination temperature and humidity sensor. That's why it's four terminals. You could monitor the pin voltages and see which ones change when applying steam.

I'd expect the pin functions to be....
>ground
>+5vdc
>varies with temperature from 0-5vdc
>varies with humidity from 0-5vdc

I don't know which pin is which. I'd have to use a voltmeter to determine it or trace the circuit on the main board.

What you could do is connect the red and brown from the compressor relay along with the red wire from the fan relay right next to it.

You could post a nice big picture of the back of that sensor board.
 
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Old 07-20-16, 11:30 AM
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I did another round of testing last night, "kick-starting" the humidity sensor by breathing on it, and then placed it inside a short length of pvc pipe capped on one end with a damp rag stuffed in the other to maintain a high humidity level. The compressor did in fact stay on, and left overnight, the unit condensed enough water in my damp basement to trigger the "bucket full" shutoff. So it seems to still function as it should when it's allowed to run (the compressor gets very hot to the touch, but I assume that's normal?). The humidity display on the unit displays the target level when you're setting it (I have it set at the lowest, 30%), but then is supposed to show the currently sensed humidity while it's running. This does work when I breathe on it (I could get it up to around 75%), and stayed close to what I was measuring with another humidity meter next to it for a time, but then it will fall rapidly back to 30% - however, the compressor stays on, which seems odd.

I monitored the voltage between the two leads of the square sensor (assuming it's humidity) and it ranged from around 18.5 mVdc after breathing heavily on it (around 75%RH) down to 17.5mVdc when the sensor displayed 30%RH). The voltage between the leads of the other component on the board didn't seem to change from 2.3Vdc regardless of any change in humidity / temp. The circuit diagram does show another two-conductor cable labeled "temp" that terminates at some kind of sensor on the side of the condenser assembly, however the temp display reacts immediately to breath / steam on the combined sensor.

So it now seems almost certain to me that this combined sensor is faulty, but I supposed there is a chance that the sensor is sending the proper voltage and some fault on the main board is causing it to be mis-interpreted. But as I said before, there's no evidence of any damage to the board.

Many thanks again for bearing with me on this, at this point I'm willing to order a replacement sensor board if that seems like a decent gamble . . .

All the best
Eben

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Old 07-20-16, 08:10 PM
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Good picture. Not quite what I was expecting. Usually the humidity part of the sensor is powered...... meaning that there would be three wires to it. In your case there are two wires to the humidity sensor and two to the temp sensor.

I would change the board. It would appear that the sensor itself is bad... maybe cracked internally. If you get it from Repair Clinic.... you have one year to send it back for a refund if not needed.
 
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Old 08-24-16, 02:37 PM
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I've had to take another break from this but wanted to report back - I swapped out the sensor board with a new one from Repair Clinic (very easy task for anyone else wanting to try), and the unit has been up and running without a hitch now for several days.

Thanks again for all the help!!

Best
Eben
 
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Old 08-24-16, 04:23 PM
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Good job.... thanks for letting us know the outcome.
 
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