Login Join Maker Pro

# Where to get normally closed relay? Or something like it

#### LVGRelay

Jul 6, 2015
3
Hello, first post and am really frustrated.

I've had experience wiring in NO relays in my car that provide power to something when I flip a switch, etc.

But this time I need something that will disconnect a line when there is power to it, so basically a NC relay, that provides continuity when the car is off, but when the car gets ACC +12V, the circuit disconnects.

Think of a line. And halfway in that line, I need a switch or relay that will cut off power to that line when the car is on. A manual switch is not an option.

Radio shack, amazon, ebay, nobody has a NC relay.

I feel like my inexperience is telling me that a common auto relay will work, but I'm just so frustrated I can't think of a solution.

Any ideas? Thank you all,

#### Minder

Apr 24, 2015
3,334
There are literally 1000's of NC relays out there, just about all manuf make them.
They generally have a NO NC and common.
You just ignore the NO if not needed, if using automotive relays there are two basic types in use, SPST (NO) and SPDT (NO & NC), generally you can get a hand full at a wrecker for a couple of .
I can give you what to look for in an automotive type if needed.
OK the automotive type has contacts 85/86 coil and 30 Com 87 NO 87a NC
M.

#### Tha fios agaibh

Aug 11, 2014
2,242

Usually 87a pin

Last edited by a moderator:

#### Minder

Apr 24, 2015
3,334
No that is single pole, single throw, you need single pole double throw.
That type is common in the automotive field so I would be surprised if an automotive store did not carry it?
M.

#### LVGRelay

Jul 6, 2015
3
I remember one store specifically asking for a 5 pin relay a while back and they said, "I'd have a hard time finding one of those, don't think we carry it." I'll try again today.

BTW - is it safe to have 12V running through these relays to keep them open all the time? Do they start to overheat and wear out?

FYI, the idea behind this project is to prevent the power door lock switch from sending 12V somewhere while the car is on, but when the car is off the 12V can travel freely.

Thank you all, I'm on the right track now.

May 8, 2012
4,960

Replies
10
Views
2K
Replies
7
Views
67
Replies
6
Views
151
Replies
11
Views
433
Replies
2
Views
494