I’m looking at this micro switch. There are four screws under the cover in basically the same format as the picture on the cover. The switch has three positions, neutral, forward, backwards. Without going into any detail on my specific situation (as not to confuse the question), can anyone decipher the arrows?
I can fill in the rest later, but very quickly, I have one of these switches in service right now. I’m having some issues with it. It would make my life about 100 times easier if I knew what the arrows meant rather then taking about a bunch of junction boxes in some very inconvenient locations to trace the wires back to where they come from and go to. I can fill in the rest later.
Makes some sense. This is a door switch on a walk in freezer. When the door is opened (switch goes to neutral) the blowers shut off. Here’s the thing though. There are 3 wires coming into this. It seems odd that a switch for cutting/sending power to some fan motors needed three wires. I was guessing that there was a relay inside that needed power all the time.
IIRC, 3 was always hot. 4 was hot when the switch was not in the neutral position and, ummm, I can’t remember what was going on with 2 off the top of my head.
The switch was malfunctioning in that the blowers were staying on in all positions. I found it was full of ice. I removed the ice and it was working again. Later, it stopped working, I found that I didn’t get all the ice out, so I cleaned up the rest of it (I think) and noticed a lot of arcing by the contacts and figured I should probably replace it. Then it stopped working again so I’m definitely going to replace it now.
The reason I was asking is because I wanted to know which wires to jump to keep the blowers running while I replaced it. Then I realized that was brain fart because I can just take the cover with me to Grainger to get the new part and leave the rest of the switch in place (then I found it on Ebay for about $100 less).
Makes sense. It’s been in a freezer and subjected to lots of swinging temps and moisture. It’s held up for probably 20 years now, being cycled probably 10-15 times per day. It’s been a good little switch and hasn’t been replaced at least since it’s been in my possession.
Another quick question, am I correct in assume that 1 and 2 have no electrical connection whatsoever to 3 and 4? If that’s the case the third wire is a mystery…I might just have to figure out where the hell it goes.
Also, why does it say “use same polarity”? I assume they are referring to 1 and 4. Is that just for consistancy? Makes me wonder if the two sides do interact with each other.
If this switch is attached by flexbile conduit, it could be a ground wire. What are the colors of the 3 wires?
The “Datasheet” link on that Allied page is confused - it refers to the switch alternately as a SPDT or a DPDT. It’s neither - it is a pair of SPST’s with alternated operation. I’ve put a PDF of the relevant catalog page here. To summarize, 3 and 4 are completely isolated from 1 and 2. When 1 and 2 are connected, 3 and 4 are disconnected, and vice versa.
The three wires are black and then two colored wires (not green or copper, I think they are orange and red maybe). The switch is connected by (grounded) BX.
Also, wouldn’t two SPST, when working off of one switch be SPDT? You move one switch and it changes the state of two things.
I’ll have to look into that third wire, maybe I can figure out where it goes. It could be for something that was never reattached after we moved the freezer, I can’t think of anything you’d want to turn on only when the door is open other then the lights, but they have their own switch.
In SPDT, there are 3 contacts - the NO (Normally Open), NC (Normally Closed), and C (Common). Thus, you can’t use it for 2 completely different things - they have to permit having a wire in common.
switch in question is 2 spst switches with a single actuator, one normally open, the other normally closed. the 2 switches are isolated and use 4 wires. it could be wired with 3 wires to act as a spdt switch if one wire went to both switches.
i see i’m slow on refresh and typing and terry replied with a similar answer.
My guess would be that the normally open contacts are controlling the blower so that when you open the door the switch goes to the open position and turns off the blower. When you close the door the normally closed position opens and keeps the lights off. I would also guess that the red wire is jumped inside the switch between two and three because red usually indicates hot AC power. Also I would have to think, not knowing the size of the fridge, that there is a relay somewhere because the switch is rated at 10 A and most of the ones I have seen have more than one blower fan.
I mean no disrespect by this, but I have to add that if you are having such a hard time with a simple NO/NC limit switch maybe you should call in the pros. This could become a dangerous situation messing with electricity and could present a hazard when you are done.
Just wrote out this big defense of why it’s not an issue, but those kind of things tend to get picked apart on this board.
Let’s just leave it at…Changing out the switch is not a problem for me. If you look at the OP, I was just curious about what’s getting switched since there were three wires as opposed to two or four. But, regardless, two wires, three wires, 150 wires, turning the power off and changing the switch really isn’t a big deal.
Now, if I had asked how to tell if the power was off to the switch or how to test the switch to tell if it’s bad, you’d be right to tell me to talk to the pros. But this is something I’ve been doing for over 15 years, it’s just the first time I’ve encountered this specific situation. I only asked because I was curious, I really don’t need to know to swap out the switch.
No big deal, I know it’s hard to judge peoples experience over a message board. Like I said, I’m no stranger to electrical work, I also know I can swap out the switch without having any idea what wires to what (I can still troubleshoot it to find that it’s not working), I was just curious.
I ordered a new one on Ebay for $46. I’m more then likely not going to do anything until I have it in my hands. Luckily it failed with the blowers running. If I’m up to it, I’ll see if I can figure out what the other wire does when I replace it. Of course if the switch fails open between now and then I’ll have to figure it out so I know which wires I’m jumping to keep everything cold.
New switch is installed. I never did find out what the third wire does, but I did find out as I removed the old one that the two sides have a jumper. So, something is losing power when the door is opened (the fans) and something is getting power (the two sides share a hot wire)…but I didn’t take the time to find out what it is.
I did find out that the new switch is ever so slightly different. As I mentioned in the OP, the original switch can go in either direction, the new one also goes in either direction, but I noticed it only clicked in one direction. Not sure if it’s faulty or by design, but I wasn’t too worried about it. After I installed it, I decided I should close myself into the freezer to double check everything…turns out the door trips the switch in the wrong direction. I’m glad I noticed that. Luckily all I had to do was move the thing that pushes the switch so it goes the other way.
I am kinda curious about what it’s turning on when the door is opened though. The only thing I can think of is that maybe it controlled the lights at some point. I can’t think of anything else that you’d want on when the door is opened.
Oh well, I really didn’t have the ambition to look any further. Perhaps someday I’ll run across the other wire. (and wonder why the hell it isn’t getting any power…wait, now it is…nope it’s dead again)