Protecting absorption refrigerators PCB

[Andonso]

The last few years during the storm season I've been having issues with my refrigerator (Norcold N641) not working temporarily.

At first I thought there was something wrong with the PCB as the frig would all of sudden stop running and not turn on.

However this problem would only occur during a rain storm with higher than normal wind.

The problem has been occuring once or twice a year during the fall or early spring when we would get a few rain storms with wind.

After further inspection I found the PCB was getting wet. It appeared rain would enter the frig vent due to higher than normal wind.

Not much, but it seemed enough that additional moisture effected the pcb and wiring inside and the frig would just turn off and would not turn back on.

I inspected the rear of the cooking and there was both AC and DC going to the frig.

At first I thought I would need to replace the PCB, but after allowing everything to dry out the frig would start to operate normally again.

This problem occurred again last night so to be safe I moved all the food from the N641 to another frig inside of a cargo trailer.

The PCB cover currently isn't bolted down but fits tight around the PCB. I'm looking into trying to add additional protection to the PCB and other wiring going to and from the PCB because I'm not certain exactly where the problem with moisture exist.

I guess it's possible there's something wrong with the PCB and/or wiring however the problem in the past has only occurred during a rain storm.

I'm thinking perhaps of getting a backup PCB as Norcold has a new PCB that can be found new for under a hundred dollars that fits many of the Norcold units including the N641. The original PCB runs around ~$200.00 new.

The other thing I'm thinking of doing is to coat the PCB with an coating designed specifically for electrical circuit boards.

One type is called Conformal Coating that comes in different versions, usually in a 2 oz bottle with brush.

MG Chemicals Silicone Modified Conformal Coating 55 ml Glass Bottle w/ Brush Cap

Another one I found is "CRC Urethane Seal Coat Viscous Liquid Coating", 250 Degree F Maximum Temperature that comes in a 11 oz spray can.

Once applied both types are suppose to keep the circuit board dry and help protect it from moisture, water, dirt, dust, etc.

I haven't tired using either type yet and recently ordered some of the CRC in the 11 oz. spray can.

Anyway I'm going to try and build some sort of water shield for the PCB apply the coating.

[mike-s]

I had a similar issue with a thermostat - moisture would condense on the PCB and cause issues.

Clean any dirt/corrosion with isopropyl alcohol ("rubbing alcohol") and q-tips. Cover any connectors/contacts/switches with tape, then spray it with a clear spray paint. That was alluded to with the comments about coatings, but you don't need to go to the trouble of getting a proper electronics conformal coating - a couple of coats of clear spray paint from the hardware store will work fine.

[Andonso]

No problem with the wiring.

The Norcold working just fine no problems and the pcb is now protected and waterproofed the crc conformal coating.

I seemed to have misplaced pcb cover machine screws. Some absorption frigs don't have a pcb cover, so I'm not certain how important it is and if it tends traps moisture or not.

[Andonso]

Gjac wrote:
I think your problem as you described it is more with the wire harness connections rather than the soldered components on the board it self. I have always used an eraser to clean that green corrosion off of my terminals. I had a similar problem on my connector and cleaned it this way. The only green stuff I see from your pictures is right above the 16 pin connector. I am assuming they were taken after you cleaned the board. Was that green stuff over the whole board or just were we see it now?

After the pcb was thoroughly cleaned I sprayed some of the CRC Urethane Seal Coat Viscous Liquid Coating on it.

However the CRC Urethane Seal Coat Viscous Liquid Coating is red in color and hides any lettering, marking, part numbers from the pcb.

The MG Chemicals Silicone Modified Conformal Coating 55 ml Glass Bottle w/ Brush Cap is more expensive but it's suppose to be a clear coating.

Anyway the Norcold's N641 pcb is all fixed now and waterproofed, so hopefully won't see any more mold and mildew problems.

[westend]

FWIW, if I see dicoloration on a PCB, I break out the flux cleaner. If there is oxidation present on connections, I use Caig Deoxit D5 in a spray can. AFAIK, Caig Deoxit is the only electronics cleaner formulated to remove oxidation. There may be others but Deoxit is a good product and readily available, either online or at Guitar Center stores.

[Gjac]

What I was referring to was the connection where the wire harness actually connects to the board not the wire harness itself. The green that your recent photos show looks like corrosion not mold. Just unplugging and re plugging connection will remove enough of the insulating corrosion to get a good connection again for a while. If that much corrosion forms on the leads of the soldered components I would imagine the corrosion inside the connectors where moisture can be trapped would be worse. I would focas on cleaning the connectors both male and female, then preventing the moisture from causing corrosion inside.

[Andonso]

Gjac wrote:
I think your problem as you described it is more with the wire harness connections rather than the soldered components on the board it self. I have always used an eraser to clean that green corrosion off of my terminals. I had a similar problem on my connector and cleaned it this way. The only green stuff I see from your pictures is right above the 16 pin connector. I am assuming they were taken after you cleaned the board. Was that green stuff over the whole board or just were we see it now?

I don't think it's the wiring harness other than perhaps the plug connector has some corrosion of which most I was able to clean, but there is still some green spots on the plug.

The problem with the PCB has only occurred perhaps one or twice a year when it rains heavily and often with high winds. The percent humidity is probably 90 percent or higher.

Some my previous pics for some reason wouldn't upload pics with the green stuff from one of the chips. which I cleaned the best I could with electrical contact clean and a toothbrush.

I was able upload most of the pics to another gallery which does shows the green stuff on the pins of one of chips. (after it was cleaned)

Chip with green stuff

If the clickable link doesn't work copy and past the url listed below.

Link to gallery: https://postimg.org/gallery/lqpttkzw/

[Andonso]

Gjac wrote:
I think your problem as you described it is more with the wire harness connections rather than the soldered components on the board it self. I have always used an eraser to clean that green corrosion off of my terminals. I had a similar problem on my connector and cleaned it this way. The only green stuff I see from your pictures is right above the 16 pin connector. I am assuming they were taken after you cleaned the board. Was that green stuff over the whole board or just were we see it now?

No the refrigerator is now working the problem afaik is only with the green stuff (corrosion) on the pcb.

Yes those pics are after I cleaned the PCB. I'm not able to get an eraser near the green stuff. I'm thinking of using some Clorox, perhaps some navel jelly and perhaps try some vinegar and scrub some more with a toothbrush. However it really requires a stiffer brush so I'll try and find a brush with fine bristles made from metal such as copper or other.

Possibly I can clean the green stuff with a fine metal pic.

I'm fairly certain there's no problem with the wiring as most of the time the refrig works, the problem usually only occurs during and after a rain storm which usually only occurs once or twice a year.

[Harvey51]

One summer our fridge vent leaked and I had to sponge up a cup of water every hour while it rained. The cause was failure of the seal on the base of the vent so water on the roof could sneak in. I patched with a bead of Dicor sealant and a strip of Eternabond over top of it. I meant to remove the vent and fix it properly but it hasn’t caused trouble again.

[Gjac]

I think your problem as you described it is more with the wire harness connections rather than the soldered components on the board it self. I have always used an eraser to clean that green corrosion off of my terminals. I had a similar problem on my connector and cleaned it this way. The only green stuff I see from your pictures is right above the 16 pin connector. I am assuming they were taken after you cleaned the board. Was that green stuff over the whole board or just were we see it now?

[Andonso]

I was able to get the Norcold N641 working again.

However even though it was cleaned up with CRC Electronic Cleaner there is still some green mold/mildew corrosion that I want to remove before applying any conformal coating

Even minutes amount of mildew/mold will eventually spread itself if not 100 percent cleaned off. (The same sort of thing happens e.g. with cameras and lenses.)

Below is a link to photo gallery with pics that show remaining PCB mildew/mold (doesn't appear like much, however from my experience this amount of mold will eventually spread itself and take over the entire PCB if left alone long enough.

Pics of N641 PCB

As you can see from some of the pics there is still some green mold/mildew corrosion on one of the chip pins and some slight green left on the plug.

I think I may be able to kill and neutralize the rest of it with some Clorox and navel jelly perhaps some vinegar.

[Andonso]

77rollalong wrote:
there is electronics cleaners i have used that work quite well , i kinda surprised the board is not coated with some sort of epoxy thought, the contacts for the connections could be coated with a dielectric grease to keep moisture out .

No the PCB isn't coated with anything, the board material with holes that the circuits are attached to yes, it's covered in some thin lacquer type substance.

I have some CRC electrical cleaner, perhaps there are better ones?

Using dielectric grease directly on circuit board isn't a good idea. On electrical contact yes, but directly on circuit boards, No. Even though dielectric grease is an insulator it doesn't insulate one hundred percent so any sensitive circuits might be effected as there is small amounts of conductivity. Also dielectric grease tends to attract dust and small particles some of which can be made from metal.

A conformal coating on the other hand is designed to be applied to circuit boards and there are different types and thicknesses that can be applied as some circuits may require certain amount of thermal transfer such as heat sinks, etc.

https://www.electrolube.com/technical-articles/conformal-coating-of-printed-circuit-boards/


Below is a pic of a similar pcb for my Norcold. Under the 16-pin plug there's some slight corrosion I haven't yet been able to clean off and also some of the chip pins soldered through the boards holes still have some leftover of corrosion.

If applying a conformal coating you want to try to get the board 100 percent clean, any leftover residue, rust, corrosion, mold, mildew, will become trapped by the conformal coating and potentially can effect the circuits.

Pointer to image

[77rollalong]

there is electronics cleaners i have used that work quite well , i kinda surprised the board is not coated with some sort of epoxy thought, the contacts for the connections could be coated with a dielectric grease to keep moisture out .

[Andonso]

After removing the PCB I'm finding green mold on some of the chip legs and a some near the 16-pin plugin.

I'm not certain the best approach of removing the green mold which seems to be stuck to some of the chip legs solder into the pcb.

I think what may have happened is the pcb became laden with moisture so many times a year over many years (10+) where green mold/mildew developed.

The RV is kept most of the time in a climate with an average annual precipitation of approx 70 inches. The climate much of the year has around 80 percent humidity.

I thought I had cleaned off any green mold and mildew however I guess not good enough as it seems just enough has stayed on the electrical contact posts which reacts to any moisture surrounding the pcb. The PCB cover isn't air tight so any moisture in the air may effect the pcb with even small amounts of green mold/mildew which is essentially a very fine corrosion.

Overtime the mildew keeps building up even if there's no water that comes in direct contact with the pcb. During a heavy rain storm the humidity increases to 90+ percent and the pcb with even small amounts of fine mildew chemically reacts to excessive humidity.

I've removed the PCB but it may be difficult to completely remove the green mold/mildew (corrosion) that become attached to some of the chips legs soldered into the PCB. I've tried using some electronic contact spray and a toothbrush. However I'm not certain how well that working.

I probably need to soak the pcb in a solution that will neutralize the mold and fine corrosion without effecting the pcb and it's electronics.

Perhaps a naval jelly? Which essentially is phosphoric acid that turns the mold & corrosion into iron phosphate which then can be flushed away with some electronics spray?

So essentially I think the pcb even though protected somewhat from direct contact with water is reacting to higher humidity over many years enough that small amounts of corrosion (green mold) develops.

Once I'm able to totally clean the pcb and apply a coat of Conformal Coating should help prevent the corrosion (green mold) from developing in the future.

[Andonso]

ScottG wrote:
Better to protect the PCB from getting wet at all.

Yeah but I can't choose the weather. I'm next to the Pacific Ocean winds can typically get to be around 40 to 60 mph. A number of years ago there was a storm and the winds got up to 120 mph flip over a few 5th wheels I guess weren't tied down good enough

I'm planning on sealing the cover perhaps with some sort of silicon. I'm not certain the existing pcb cover is good enough if ~50+ mph winds are going in all directions up, down, sideways, underneath and over the top of the RV I think the rain is being forced through the frig vent and ends up effecting the PCB.

I was thinking of installing some sort of cover over the vent but I'm not always around the RV to remove a cover when unneeded. Absorption frigs need to be level and won't operate correctly without enough air flow.

I looked around for an electric but all are either too small or too large. The frig is mounted off the floor near a wheel well so it would be impossible to somehow mount one on the floor.
Anyway I'll try to devise a internal cover over the existing pcb cover that won't restrict air flow.

The PCB, even a small amount of water or moisture can prevent them from working. I was hoping as an added protection the conformal coating will prevent problems in case the PCB become wet again. However I'm uncertain how well a coating would work to protect the PCB plugs contacts and wires.

Currently the frig won't turn on as I can see a very small amount of some moisture one to two drips from the bottom. It appears moisture somehow got inside onto the other side of the PCB between the PCB and what it's mounted to.

I'm hoping it will start working again once the weather gets better and it has a chance to dry out.

I think absorption frigs are great for traveling but they can potentially become a nuisance for full timing and cost more to run than an electric.