Moisture in instrument cluster

[dirtrod]

Yep, same here in Coquille on the southern Oregon coast. My JD is a model 4200 and was told the same lame story by the dealer.

 

[Cidertom]

The technical name for the cause is "dinural pumping". The communications waveguides (WG) I deal with could have it... if I didn't take steps to prevent it. Basic action is: Air filled chamber heats up over the day. Causing air to expand, and it pushes out through any opening. After the sun goes down the chamber cools off, causing the air pressure to go below atmospheric which causes the air to be "sucked in". Problem is that the thermal mass of the chamber walls (and attached enclosure/tractor/?) does not cool off as fast as the outside air. Since the outside air temp is dropping, the relative humidity is going up, so the air drawn in is moisture laden. As the night continues to cool down the moisture now inside the chamber condenses and forms water droplets. The next day the chamber starts to heat up forcing air out again. The heat necessary to vaporize the water lags behind the heat necessary to force the air out, so the chamber becomes saturated. The cycle keeps repeating. We have multiple O rings and seals on the WG and it still happens. The way we keep it from happening is 1: We pressurize the WG with either dry air or nitrogen to 2-4 psi (some more, some less). It just has to exceed the differential pressure created by the heating. 2: we install a desiccating plug. This device is a hollow pipe (about the size of a screwdriver handle) filled with desiccant. As the air expands (remember it is dryer now) it dries out the desiccant on it's way out. As the air starts back in the desiccant drys it out. Since it is easier for the air to travel through the plug it leaves the other seals intact.

More than you ever wanted to know. My 4300 did the moisture thing as does the 4520. I'm thinking of installing a desiccant port on it.

 

[George2615]

Park it in the sun for an hour or two before you put it away and the moisture inside your instrument panel should evaporate.

 

[mars1952]

"dinural pumping".
More than you ever wanted to know. My 4300 did the moisture thing as does the 4520. I'm thinking of installing a desiccant port on it. (post #12)

Hi Cidertom: Thanks for the informative post! I have considered taking my JD 4300's instrument cluster apart and putting in a small desiccant bag. Does anyone know if there is any room in there? I think that the port would work better. Where can I get a desiccant port?
Thanks, Marshall

 

[Cidertom]

I will look through my suppliers cat today and see what I can find for the 1-2 buyer. One other thing that >might< work is to put drain holes in the lowest part to allow the mositure to escape. That works for the tower mounted boxes, they have a coulpe of 8-32 sized holes in the bottom and they stay dry. While the moisture might still form, the holes being at the low point would let it get back out.

 

[BTDT]

What about a 12v light bulb attatched somewhere out of site but dissipating heat into area (on all the time key on). Maybe this would keep things warm/dry enough to eliminate problem. I know a brake light bulb can get plenty hot if it's on all the time.

 

[BillyP]

Whatever the fix is I wish someone would let JD in on the fix. This same problem has been going on for a few years now and they don't seem to care. Same thing with the fuel gauge...