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Discussion Starter · #1 ·
I have a Daewoo mini split …. Model number DSC-F1201 JLH-V
I believe also called DSC-1285FLH... Purchased June 27, 2019

Unit stopped working properly a few weeks ago. Called a repairman last week. Repairman have been here twice, checked coolant and tried to troubleshoot but problem persists. The repairman tells me that the unit has the right amount of coolant.
Since the repairman have been unable to fix the problem, I have done some additional troubleshooting.
First of all, the unit never seems to be doing the same things every time, but generally this is what happens.

When I set heat, the unit usually just blows ambient air. (Even after 30/40 minutes) The only way I can get it to blow ‘warmer’ air is to turn the unit off wait a few minutes and then turn it on. By repeating this procedure 5 to 8 times I am able to progressively reach higher temperatures. However the highest temperature is still only 15/25-deg F higher than ambient.

(On a warm day when I select the cooling cycle, it appears to work but the cooling air is about 20-F cooler than my other unit.)

I checked the 4 way valve, seems to be working fine. When I remove the selenoid it cools very well.

1) ) Once I get the unit to pump air around 85-F, occasionally I can get it to go up to about 100F by dipping the Thermister probe into ice water.
But, after 15/20 min the exhaust air cools and it will not start warming up unless I turn the unit off and restart it. ...... Also when I remove the probe from the cold water the air temperature often drops. That is why I think the problem night be with the thermister (ambient air temp sensor), or with the power control board.

2. Have been unable to find the part numbers for thermister or for the Power Control Board The unit is a Daewoo DSC-1285FLH can anyone help? Are these generic parts ?

4. I have a similar (not the same brand) unit that is working fine … I have considered, but I’m reluctant, to swap thermisters to isolate the problem. I would prefer just test the suspect one, but I do not know what the resistance is supposed to be.
 

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According to the manual, you will get an E1 error on display or the running light will flash 1 time if the room temp. sensor has failed.

If you don't have the manual, click the link below to get it:

Service Manual
 

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One possibility is to make sure the thermistor is not touching the coil fins or tubing. It must be in free air at ¼" or so away from any contact. If it touches, it will cause the unit to short cycle. Sounds like that may be something to check.

Otherwise, get a reading of the resistance of that sensor while at 72° F. or there about. That will be helpful if/when you call their service number.

It sure sounds like a bum thermistor but it could also be the control board. They should change the parts and get on with it.
 

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Discussion Starter · #4 ·
Thanks for the replies...
I have not seen any error codes.
Actually I am not positive where the error code would appear ....
Does anyone what the resistance is supposed to be at various temps.?
The thermistor has been hanging free of obstructions
I have gone through the manual.... The manual does not show a part list or part numbers... Where would I find part numbers for the Thermistors and control boards.....
I have tried calling the service number, no help. I DIY installed they will not honor the warranty. Even though i do not believe this could be a problem caused by installation
 

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If you have the model with a display panel, the error code will show on it. Otherwise, there is supposedly a run light that flashes the code number every 8 seconds during the shut shutdown term.

That's all I know from reading their manual on-line. They show all the parts in that manual but don't give part numbers or any specs. :sad:

From the manual:

"How to order spare parts
To have your order filled promptly and correctly, please furnish the
following information:
Model No. with Indoor or Outdoor
Part No. in the Explosion View
Part Name
The quantity you ordered"

Not the way to treat a customer.
 

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If it helps any, a general purpose standard of the refrigeration/hvac industry Ranco thermistor is listed at "Nominal Sensor Ohms @ 75F: 30 K" so you might compare to that.

I think it will have a negative temperature coefficient so probably will go down fairly fast with lower temps. I see several others listing their resistance as 12K at 70° F. so take that for what it's worth.

If you use simple math to calculate the temp.resistance slope using those values in the examples above.... 18k/5° = 3600 ohms change per deg. change. See how that compares, if you want to play with it.
 

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Discussion Starter · #7 · (Edited)
Thanks,
the answers here got me a lot closer ... I will try to test the resistance see if the results at least appear to be reasonable even by interpolating. I have not seen any error codes or flashing display.

As far as ordering parts unfortunately in the exploded view the numbers do not correspond to the diagram. For example: part # 22 is labeled indoor motor cover, but appears to be the sensor, part# 20 is labeled sensor holder, but appears to be the PCB. Besides I hate to even start ordering parts till I have some idea of what is broken.
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It's a new unit, looks to be built to be disposable as much as fixed.
It would be so much easier to just buy a new unit. It just goes against my grain. I am glad to see people here who seem to feel the same .
Any further suggestions are appreciated.
At this point it is as much about curiosity and because I have a feeling that it could be just a matter of swapping a simple component to get it resolved. Without all the proper testing equipment and and experience it is an uphill battle.
Thanks again all!
 

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Their parts presentation does seem to be confusing.

With deep determination, I find that the sensor you are dealing with is listed on the "6. EXPLOSION VIEW" diagram as part #19. It's part of the 15 thru 22 group.

Thermistors do fail, so there is hope that the fix will be easier than the part acquisition.
 

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Discussion Starter · #9 ·
Well, thank you,
But, most of the drawings do not really look or correspond to what the actual parts look like...
For example # 21 appears to be the elect. box not the motor ... #23 is the vent actuating motor not the drainage hose, not sure what 26 is, but it is not the remote controller, etc.
The thermister actually looks very much like part # 22 not #19 ...
#19 looks more like the transformer not the thermister.
 

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Actually, there is no parts list there for the FLH version so it would be hard to know for sure. The only list the show for the indoor unit is for the FL version. I assumed the indoor sensor would be the same. I assume we both know how assuming sometimes works. :smile:
 

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Discussion Starter · #11 ·
An update... The unit is still doing the same thing... I am well beyond my expertise level.
As a last resort I took the temperature probes from my other unit, even though the plastic plugs were different I carefully removed and swapped the leads ( More importantly I was able to put them back without damaging that unit)

I tested both sets of Thermisters ---
Daewoo: @ 76F 2.3K Ambient -- 2.0K Pipe @ 35F 5.3K Ambient-- 5.5K Pipe
Frikko : @ 76F 6.3K Ambient -- 5.5K Pipe @ 35F 15K Ambient --15K Pipe

I then installed the Frikko thermisters in the Deawoo. It continued to operate erratically.
One last thing. One of the temp leads at one point worked loose, I finally got an error code to show up.(E2) it was displays on the Front panel display where normally you would see the temp. Code disappeared once I resealed the lead.

I would have liked to fix the problem, but long term, learning so much about something I did not know anything about, is way more valuable.

I really appreciate all the help.
 

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According to the manual, the error code E2 means the IPT (inside pipe temperature) sensor has failed. You may be working on the wrong sensor. The manual says an E1 error means the RT (room temperature) sensor.

Look for the RT sensor and see that it isn't in contact with the coil or tubing. It needs to be held away by at least ¼", more is better.
 

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Discussion Starter · #13 ·
Thanks,
The RT sensor is not in contact with the vanes. I tried different locations, including ice water.
The reason I got the ER2 code is because one of the contacts for the PT had loosened, once I reinserted the code disappeared.

Not only did I swap the PT and IPT between the two units, but since the 2 Daewoo probes had similar values I tried swapping between them with each other.
Since I do not know what the resistance for the probes is supposed to be, but since both are in the same range, and unlikely that both would fail, I am starting to suspect that the problem is elsewhere. The next obvious item would be the control board. I have no clue how to test it.
 

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It agree that your control board may have failed. It'd be a monetary gamble to condemn it without knowing for sure unless it's in warranty. I would lean toward replacing the RT sensor first. It is responding as if the room temperature is much higher than the measured temperature as determined after its initial short test run. That explains why you can jack the temperature up by initiating numerous restarts since it operates in full on mode during that time period.

Apparently to make this initial test run take place, you must shut the system down for 3 minutes and restart it. Then it will run in heat mode until some predetermined time and either shut down if it thinks your set point is low enough to not be demanding heat or continue to run if your set point is high enough to be demanding heat. I suspect you knew all that but just wanted to be sure.

edit: I missed the part where you switched the 2 thermistors of the Daewoo unit... that makes the board look like the culprit more than ever. Like you said, both of those sensors would fail in concert.
 

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Discussion Starter · #15 ·
Really hard to figure, because the unit never quite behaves the same way.

For example this morning during the first 3min, the evaporator warms up to about 150F but after 3 min. when air starts flowing, the coolant line coming out if the outdoor 3 way valve ( and everything downstream) cools down. From about 115F to 80 F; even if I immerse the RT in ice water.

Because I get varying results, I lean towards faulty electronics, truth is I really have no idea.
On page 14 of the manual I see that the 2 temp. probes feed information to something called "CN6" that might be the inverter or something that feeds data to the inverter that controls the unit. I have no idea what this "CN6" looks like. Or if it is faulty.

The tech on the first visit added some coolant, not sure how he decided the right amount..
 

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The tech on the first visit added some coolant, not sure how he decided the right amount..
Minis can’t be charged by pressure. So he may have done this out of desperation.
The only way to really to check or adjust mini split refrigerant charge is pull and weight the refrigerant.
It’s the same with their big brother VRF equipment.
In fact, I spent Friday pulling the charge on a 9 head Samsung VRF system to verify it was the problem. 60 lbs worth of R-410A.
 

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In fact, I spent Friday pulling the charge on a 9 head Samsung VRF system to verify it was the problem. 60 lbs worth of R-410A.
Egad! That would take all day, not to mention lugging the recovery tank and weighing it had to be a bummer. It's making retirement feel all the better now. :smile:

Let me know if you need any help, I'll run and hide! :wink2:

ps. I like your alias, roughneck, since I actually spent a few years of my youth roughnecking in the oil patch in several states. Fond memories but not the safe clean way to make the big bucks.
 

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Egad! That would take all day, not to mention lugging the recovery tank and weighing it had to be a bummer. It's making retirement feel all the better now. :smile:

Let me know if you need any help, I'll run and hide! :wink2:

ps. I like your alias, roughneck, since I actually spent a few years of my youth roughnecking in the oil patch in several states. Fond memories but not the safe clean way to make the big bucks.
Wasn’t all that bad. 3 or 4 hours with the pump running. A quick evac to 900 microns and we were back running with virgin gas.
The systems been troubled. Lots of contamination and other issues.
 
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