The International Cessna^® 170 Association

I just read an article in the current Cessna Pilots Association magazine saying that the seal at the rolled-edge of a can-type master or starter solenoid/contactor is not perfect and that "water can and does get into" them. It recommends use of a sealant over the rolled edge to prevent moisture entry. Apparently Cessna used to use a sealant, but no longer does. The article recommends fuel tank sealant like ProSeal, but says "there's a rumor though that if you go to the Aviation Department of Home Depot and buy some rain gutter sealant, it will work just fine." It recommends against RTV sealant as it dissolves with mineral spirits. Fuel tank sealant is too expensive for this small use and the rain gutter sealant I saw at my big box hardware store was essentially RTV sealant. Anyone else use a sealant on their solenoid(s)/contactor(s), and if so, what do you use? Obviously it needs to be fuel and oil resistant. I'm interested in what others think of this issue.

Gene

I would think that any quality oil/heat resistant sealant would be more than adequate. It would be easy to monitory its condition over time based on the solenoid's location. If it started to break down or need a touch up application, it would be easy to do.

My .02 worth

Jughead

See last entry here.

Geeze, I read that thread at the time and that part didn't sink in. And it was only a month ago. Thanks, Gary.

It's interesting to see that this problem is nothing new. Here was Cessna's solution to moisture in the contactor back in 1960.

Hmmm, kind of defeats the purpose of the sealant.

I've owned/maintained three Cessnas ...none of which had sealed relays...and never had a single problem with them.
I also don't mount them upside-down like some questionable articles have recently proposed. (If the label is upside down... then why does all the literature show them with the cap on the top? Not to mention that if they're mounted with the cap on the bottom... they'd be more susceptible to retaining water and therefore some newcomer might think they needed sealant.)

Please note, the Cessna relay depicted with a "vent" is a different type than modern Lamar types. The vent on electircal relays is not for drainage...it's for atmospheric venting to reduce ozone which promotes internal corrosion. (After all,...they are mounted in dry locations.)

gahorn wrote: I also don't mount them upside-down like some questionable articles have recently proposed. (If the label is upside down... then why does all the literature show them with the cap on the top? Not to mention that if they're mounted with the cap on the bottom... they'd be more susceptible to retaining water and therefore some newcomer might think they needed sealant.)

George, it sounds like you may have read the same article. So those contactors with the supposedly upside down labels were intended to be mounted with the cap/rolled lip at the top?

(For anyone who has not seen the article, another thing it says is that the contactor should always be mounted with the cap/rolled lip on the bottom so that gravity helps the spring to hold the contacts open when the coil is not energized. In other words, with the terminals toward the bottom. According to the article, LAMAR installed the labels on contactors upside down causing mechanics to install them with the cap/rolled lip on top. [But for copyright, I'd attach the article.])

The Sky-Tec master solenoid that I ordered from Spruce just came and its label is oriented the same as the supposedly upside down Lamar ones. The diagram enclosed with it shows it oriented with the cap/rolled lip (and terminals) at the top. So I looked up Cessna service kit SK210-173A for the contactor and it shows the solenoid oriented with the cap/rolled lip at top. What, did everyone get it wrong? I think the authors of that article are all wet and orientation is a non-issue. But I'm no expert. George can weigh in and have the final word if he likes.

OLE GAR SEZ - Them what thinks they know everthing reely pisoff those of us that do.

I've made a few erroneous comments in my lifetime (although they are usually written in either Sanskrit or hieroglyphics) and I might be making one now.... but I've been fooling around with airplanes using these type relays for about 40 years now and I"m absolutely convinced the persons making the claims about upside-down labels and how the entire industry has been mounting relays upside down because of it are full of .......... themselves.