bluescortcossie

where on a car can i find a relay that is always open until the switcher point is live ?

basically i have loads of old cars about and begrudge buying a relay !

fraser9764

iTrader: (3)

you're just after a Normally Open relay?

bluescortcossie

could be ????

i cant think of what on a car would normally be on until a switch is thrown

i am trying to set up a cold start valve on my derv and need it to switch off when the resistance on the water temp sender reaches 0 (when up to temp) but to stay on until then

bluescortcossie

just a thought , would a dim/dip relay do that as they are "double throw" relays , just have the power going out of 1 outlet ??

i might be completely wrong though !

fraser9764

iTrader: (3)

so you want a normally closed relay?

not sure where you would find one already on a car but theyre only about £2.50 you tight git!!

fraser9764

iTrader: (3)

yes they prob would, have never looked at them to be honest.
just use your car battery and a multimeter to find out which pin is N/O and which is N/C

bluescortcossie

trouble is i have it in bits at moment and cant be arsed to wait for post and don't know of a maplins locally

i really dint know what relay i need , i will be running a ignition switched live to said relay then from relay to cold start valve , i need this part of the circuit to be constantly on until the "switcher" part becomes live , this will be linked to the water temp sender so that when its up to temp there is no resistance on the switcher circuit and therefore turns off the start valve

if that makes any sense !

fraser9764

iTrader: (3)

???

fraser9764

iTrader: (3)

ah shit i meant Normally closed contact on that quick sketch

fraser9764

iTrader: (3)

just noticed you said you wanted to link it into the standard temp sensor? i'm pretty sure that wont work, you really need a thermo switch (like turns your fan on)

bluescortcossie

yeah , i ment thermo switch not sender

Ive sorted it now anyway , well sort of , need a new thermo switch as mine doesn't seem to switch now , got it so the cold start becomes active when ignition on then will cut off when its up to temp (in theory when i get a new switch)

tabetha

In answer to your first post, you merely need a CHANGEOVER relay, this has TWO outputs, one is LIVE when unswitched, it then changes to the other oputput when switched, but as aid you need a thermo switch.
tabetha