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.

[Andonso]

The CRC Uerathane Seal Coat description shows

Electrical & Electonic insulator, Flexible, non-conductive polyurethane film

So I guess it's considered to be a polyurethane film. I'm uncertain why it's labeled Uerathane as there are differences between the two. Such as e.g. a polyurethane takes longer to dry than a urethane.

Anyway I would want a product that's been tested specifically to use with electronic circuit boards and comes with a temperature rating.

Silicon based Conformal coatings have a higher (and perhaps lower) temperature ratings than urethane/ polyurethane coatings , which usually have better resistance to various types of chemicals.

So if an area has high temperatures or the circuity reaches higher temps above ~250 F probably a Silicon based Conformal Coating would most likely be a better choice.

The absorption refrigerator's cooling unit I don't think would ever reach 250 deg F. so a Urethane/Polyurethane coating should work just fine.

I guess for some applications a coatings thickness can become an issue so one type may be better than another for more specific applications. I remember reading somewhere there are basically 5 types of conformal coatings which includes Urethane/polyurethane.

[ScottG]

Better to protect the PCB from getting wet at all.

[Clay_L]

Regular polyurethane spray works well as a conformal coating.
One of the companies I worked for used it. One advantage was that you could easily repair the board because it was easy to do. The coating went away from the joint when you applied a soldering iron to it.