Thread: Defrost not working after replacement parts

Originally Posted by RAJOD

I just replaced the bimetal and have had it running for about 7 hours. So far the defroster has not kicked in. I dont want to put it all back together until i see that occur.

This is a problem I see quite often. If the evaporator cover or machine compartment covers are left off, the refrigerator will not cool properly and the electronic control uses the information supplied by the thermistors to know when to start a defrost cycle (Up to 99 hours) when it is cooling properly. If the defrost heater and the defrost thermostat check good for continuity, unless your new control board is bad, the defrost cycle will work.

Originally Posted by RAJOD

Is there a way to force a defrost cycle? I can't seem to find diagnostics for this model.

Yes, but I don't have a tech sheet for that model. The tech sheet for your machine should be behind the lower kick plate on the right side.

Thanks for the reply. I looked under and did not find the tech sheet. Maybe wife put it away somewhere.

Yes I realized that the fan would push air better if the plastic duct work were in place.

The defroster did kick in at 10 hrs. I put a tiny piece of wire with a little plastic on it so i would know if it kicked it. It did and melted off the new frost.

The only thing I replaced this time was the bimetal. I don't know if old one was bad, I just ordered it just in case it acted up again.

Maybe its getting iced too much for the defrost cycle to manage. I noticed that it melted the frost off but it was very wet still when the freezer compressor kicked back in. Which would mean that water on the coils would just refreeze. Then after a month or so enough is built up where the defrost 10 min cycle is not enough to melt the frost and new ice. So while it works it does not know how much ice is actually lodged in the fins. The bimetal may open at 50F or what ever its set to open at but there still could be ice.

I also found the vent to the freezer, it is that tiny hole in the back. I just held my hand over the hole and shut the fridge side a few times. Each time I could feel a puff of air come out of it. So i guess that mean that vent is open.

I dried it out best I could but the wife wanted it back together so there is still wet areas between the fins/coils. I suppose a properly working adaptive defrost should take care of that.

The only way I can see for the fridge to get rid of moisture inside it is.

1. Freeze it to ice
2. Melt it with heater and let it drip out the bottom drain pan.

Maybe it was the bimetal, hope so.

So how often and how long do these defrost cycles usually go on a busy refrigerator? I have kids and the doors are open and shut quit a bit during the day.

I think this model has two thermistors, one in the fridge and one in the freezer. The freezer one must be tucked in up high. Id need to tear some apart to get at it. The refrigerator one tested ok so I'm assuming the freezer one is probably ok.

Its working well again, temps on fridge side under 40F, freezer under 32 and only been on a few hours.

But......

I checked the bimetal thermastat (old one) and it seems to work fine. I put in the freezer for like an hour then checked continuity and it passed.
When warm it was very high resistance and no continuity.

Which makes me wonder why the freezer coils froze up.
- defrost kicks in at like 10 hours after plugging it in which means the circuit is working, the heater element is working.
- Bimetal fine
- Fridge thermistor fine
- New computer board that controls adaptive defrost. Im wondering if the old one was even bad now.

If in 4 weeks the coils freeze up again which will result in a warm fridge what would be the cause?

any ideas?

Originally Posted by RAJOD

The only thing I replaced this time was the bimetal. I don't know if old one was bad, I just ordered it just in case it acted up again.

Out of the three defrost components, the defrost thermostat is the least likely part to fail. The most common is the electronic control board.

Originally Posted by RAJOD

I also found the vent to the freezer, it is that tiny hole in the back.

The evaporator fan blows the air into the fresh food section through the damper, back left corner. It returns through the louvers, bottom center and rear

Originally Posted by RAJOD

So how often and how long do these defrost cycles usually go on a busy refrigerator?

Ten to twelve hours sounds correct, however ten minutes is not long enough. The defrost cycle is about twenty three to twenty seven minutes. Besides replacing the failed part after the defrost fails, you need to manually defrost the evaporator. Any frost left in there will just build on itself. After a defrost repair it's best to start out with a dry evaporator. It sounds like the control board needs to be replaced on your refrigerator. Its becoming a common repair on those models.

Originally Posted by RAJOD

The refrigerator one tested ok so I'm assuming the freezer one is probably ok.

I checked the diagram and your model doesn't use a freezer thermistor. How did you check the refrigerator thermistor and what were your results?

Main Control Board 8201673 Order now for same day shipping. 365 day return policy. RepairClinic.com

I have the manual for it and it tested within the range. Something like 8k ohms at room temp. I did a few readings and it fell in line with what was in the manual.

I just replaced the control board (it was like 180.00) brand new. And I put the refrigerator on a appliance surge protector so prevent any spikes from affecting the computer board.

In terms of drying the evaporator during a manual defrost. It sort of has to drip dry, the fins are way to tiny to dry.
I was thinking next time I do it to put some kind of moisture soaking bags inside the freezer to help dry it out. Not sure what they are called or where to get larger ones but they are packed with many electronic items to prevent moisture build up.

I could replace the control board again but I can't really verify that the old one or new one are bad. I don't know if my model has crude diagnostics since it does not have numeric LED, it just has lights (maybe they could blink x amount of times) for a code like they do in cars.

I had a repairman out about a year ago and he charged like 70.00 to tell me he wanted to replace the bimetal, heater element and control board. He did not even take it apart nor did he do any testing of the unit. He just was doing a shotgun (replace it all) approach.

Originally Posted by RAJOD

I have the manual for it.... I don't know if my model has crude diagnostics since it does not have numeric LED, it just has lights

Doesn't the manual tell you how to get it into diagnostic mode? It uses the bar graph LED's for the test results. The manual should have the directions for getting into test mode for both the bar graph and water filter LED's.

Originally Posted by RAJOD

it tested within the range. Something like 8k ohms at room temp.

OK, that's not even close. Take the thermistor out of the refrigerator and connect your ohm meter to it. Place it in a small glass of crushed ice. Add just enough water to cover it. That will make it very close to 32*F. At 32*F, the thermistor should read 8750 ohms.

Originally Posted by RAJOD

In terms of drying the evaporator during a manual defrost. It sort of has to drip dry, the fins are way to tiny to dry.

Do you have a hair dryer? I use a heat gun which is a hair dryer on steroids. When you defrost the evaporator are you getting all the ice and frost build up that's behind it? Some moisture on the coils wouldn't cause it to build up frost unless there was still a lot of frost around the evaporator

Originally Posted by RAJOD

I could replace the control board again but I can't really verify that the old one or new one are bad.

Actually this is a very simple test. There are only three components to the defrost system, the control board, defrost thermostat, and defrost heater. When the control's adaptive defrost goes into defrost cycle, 110 VAC is supplied to the defrost heater, through the defrost thermostat. If the defrost thermostat and defrost heater check good for continuity, it must be the control board that is faulty. The defrost heater is like a light bulb. It's either good or bad. If the freezer temperature is below 50*F and the defrost thermostat reads closed (shows continuity) it's good. I haven't seen one that's intermittent. Unless the new control board you replaced is bad, the only thing I can figure is your original diagnosis of a defrost problem might be wrong. Other problems can sometimes make it appear the refrigerator has a defrost issue. One is if the evaporator cover is left off. If the evaporator fan motor is not working correctly frost starts to accumulate on the evaporator. A problem with the sealed system will also make a poor frost pattern that can appear to be a defrost problem

I was just guessing when I told you the temp and 8k, I did not have the manual in front of me. When I did do it I was looking at the numbers and temps and was testing the ohms. So yes it was good, it was a range of temps and ohms i tested.
0 F - it was like 20k
30 F - it was like 8.8k ohm
40 F - it was 7k

I don't remember exactly the rest but when I tested it was apparant that the thermistor was in range with the manual I had.

The manual is a general tech one for Kitchenaide side by side. It does have docs on test modes but only for models with digtal read outs.
I tried it but it did not seem to do anything. I think my model is maybe a little newer than the service manual i found, it says for KSRA22FK, 25FK.
So its not the exact service manual, it differs in the adaptive control it uses. As for the thermistor range, I am assuming those numbers are generic for many Kitchenaid models but do not know for sure.

That control board you pictured is the one I got, it seemed brand new as I even had to bend the board to fit the required mounting angle.

I've defrosted it like 5 times this year, (getting to be a routine)

When I remove the cover it is a total block of ICE. Each fin has a block of ice between it. So even though the fan is running, very little air can flow through the fins. I take all the food to the other refridgerator and let it thaw out all day. In the past I have used a hair drier to defrost it faster.

Then it works like new for a few months. When the refrigerator side gets warm I know its frozen up again.

The last time I left the cover off just to see if the heater actually kicked it. When the compressor kicks in all the fins get very cold and they all turn white (its just a thin film of frost from humidity) after 10 hours or so the heater did kick in. I am not sure exactly how long it ran though. I would need some kind of alarm to know exactly.

I can't find a service manual for my exact model so figuring out how to put it in diagnostics mode will be difficult.

The evaporator fan works well.

The control board is faulty. You'll need to replace it. Check with the place you purchased it and see if they will exchange it for you. The diagnosis mode won't help you. It doesn't check the control board, just the components. Follow the instructions for bargraph on this tech sheet.KSRS25FGBL00 Tech Sheet.pdf

Hey thanks for that tech sheet, its very nice.

I looked at it but am a little confused on the steps to put in defrost mode.

Option 1.
1 - Power off to Refridgerator for at least 30 sec. (Ok so just unplug it from wall then plug it back in)
2 - Thermostat off (Not sure on this one. My controls have a on/off, two temp buttons, ice button) So does this mean plug it back in and then press the off button on the control panel?
3. Power on to Refrigerator. - In step 2 it says thermostat off but its going to be off when i unplug it in step 1.

The way I read it its just unplugging and plugging fridge back in. That does not seem right as the defrost wont kick in for 10 hrs if I do that. I'm missing something here.

Option 2. (bimetal closed)
1 - thermostat off 15 sec
2 - thermostat on 5 sec
3 - thermostat off

Is that just the on/off push button on the control panel?