Mystery wire connections in engine compartment

[tiinytina]

Sent: 6/26/2007 5:40 PM

What the heck are these? There are 3 of them screwed to a board.to the side of the engine.  Everything was rusty  and wiggling them caused my dash fans to cut on and off, so I cut the wires and put new terminal connectors on them, new nuts, and used new screws to put them into the board. (Planning on replacing the board soon). The only marking on one of them is 20A with 226  stamped below. The lower wire on each that you see comes off of a hot battery line and the top wires disappears into various harnesses. The third one you can't see started to self destruct as I attempted to take the nut off. I called Tiffin and got the correct Solenoid (the big battery cables connect to it then split off to these) in the mail but they sent me 3 breakers (like the type you would install in a breaker box in your house). Haven't had time to call Tiffinbut did email this pic again..... I think they reused some old parts numbers on newer things at this point.
    The "things" are about 1.5" long with the two bolts poking out. They are maybe 3/4" wide and same deep.  I don't know if these are specific to RV's, Tiffin, etc... and since I don't know what they are its a bit difficult to find replacements....
thanks!
tina

[ontheroadagain]

Sent: 6/26/2007

they are circuit breakers they reset automatically after they trip which is convenient but I've seen them melt wiring and start fires because the will continue to reset until they meltdown your better off with manual reset breakers just like you have in houses

[Slantsixness]

Sent: 6/26/2007

Tina,

They are thermal fuses. Not "fuse links" or "fuses" But similar. (some people have about a dozen different names for these, but this is what it is:

There is a bimetallic strip inside, which makes contact to both terminals. When the Current rating is exceeded, (20 amps) the strip heats up and breaks contact.

When the source of the over current condition stops, the Strip cools down and reconnects.

So they are effectively "self resetting thermal fuses". If they do open up, expect to wait about 3-5 minutes for them to reset (and remove the over current condition!)

When good, these will read close to 0 ohms (continuity) across the terminals. if the are open (infinity) they are bad. This test only applies when there is no power applied. when power is applied, the voltage on both terminals should be Equal (12v on one terminal = 12V on the other terminal. If they are used for grounding, you would not see any voltage unless they were open. They should NEVER be used on a ground line.

Over time and excessive current draw, the bi-metallic strip can become weakened, or the contacts corroded and that can reduce the effectiveness of the thermal fuse. When this happens, you would experience either no current flow (open condition) or even a "flickering" condition.

These are commonly used, even today. But they are electronically inadequate as far as I am concerned. Replace them with inline resettable breakers or Slow-blow fuses if they kick the bucket. Otherwise... let 'em keep on going until they die. The two pictured look pretty new, so they're probably ok.

Tom

[Slantsixness]

Sent: 6/26/2007

Oh yeah...
Tina,
If you REALLY want new ones,

go to McMaster Carr.... they still have them (new).... I don't know why, but they still have them!! (and somebody still makes them!)

Tom

[Dave1210]

Sent: 6/26/2007

Tina;

If you can't find them, I would suggest that you stop by your local Fire Department or Ambulance squad. Fire and EMS vehicles have a lot of these, and the mechanic who fixes them will know where to get the parts.

Dave

[rustyescott1]

Sent: 6/26/2007

they are hd overload circuit breakers . they automatically reset when tripped. i n other words a reusable fuse   
rusty

[tiinytina]

Sent: 6/27/2007

thanks guys! I snagged the 2 on ebay. I'll use one and have one spare, leaving these two pictured in place.
Another question since this board sees a lot of weather being behind the grill should I put any sort of anti corrosive grease on the poles?
Thanks again!
Tina

[ontheroadagain]

Sent: 6/27/2007

yes i would.

[denisondc]

Sent: 6/28/2007

Before the auto industry used fusible-links in cars, circuit breakers like these were commonly used for the headlamp circuits and other high current loads. Like any other part, they can eventually go bad from old age, weathering, & heat. Not only are they still made, you can even buy them in 'marine and aircraft quality'; at outrageous prices.
I see crimp-on connectors in the photo. When I redo circuits on my Winnie I always replace the crimp-on's with soldered connectors, and normally use heat shrink insulated covers. They are far more trouble to make up, but are much more reliable.

[tiinytina]

Sent: 6/29/2007

Yes, I thought about soldering them on and shrink wrapping, but crimping at the time was much simpler and since I didn't quite know what I was 'fixin'... it will do for now. Since I do copper foil stained glass I'm good with the soldering iron.  Once I get the new "fuses"and cut and urethane a new board... and find the time.... I will do it right.

thanks for the advice....
Tina