latching relay?

I am Installing an A/c compressor in my car, I want it to come on with a switch and turn off when power is removed from it. Then the next time I start the car the compressor will stay off until I turn it on again with the switch. Would a 'Latching Relay' do this? If not what am I looking for. I am sure I didn't state clearly but hope it is understandable. ( the compressor clutch) Floyd

Hi, Is the A/C compressor being used for the climate controls.. A/C and heat? Most systems have a pressure switch which allow compressor operation between a low and high limit. It isn't wise to allow the compressor to operate uncontrolled, which is why they have the high limit. But if it's not being used in that application, search VW latching relay. Mark

See my latching relay as per on/off latching circuit with 2 relays. The diodes are not required if the switch handles the load current (until the relay closes). The Fused +12V would be your normal supply to the a/c switch (ie, ign +12V). The N.O. push to turn off is only needed if you want to turn it off without removing the input Fused +12V. And as Ween suggested, I'm assuming this is for the "master" a/c enable circuit - not the compressor itself - hence all pressure switches, idle-speed drop outs, cycle delays, etc, continue to operate normally.

Thanks for your replays. OK i thought it might require more explanation. This an add on compressor, I have converted it to an air compressor for air suspension. It has a pressure switch at the air tank. I want it to turn off when I shut off the engine but next time I start the car it will stay off until I manually turn it on with a switch. Thanks Floyd

Thanks for the clarification. Ween & I saw "A/c compressor" and assumed it was for an aircon. The diagram I linked - namely... ... will work fine but with a few provisos... Keep both diodes unless the ON switch can handle the compressor current. Hence the switch and its wiring need only be rated for the relay's coil current. If you don't want to be able to manually turn off the compressor (with IGN still on) the OFF switch can be omitted - ie, merely have the "feedback" wire with diode. The +12V input needs to be IGN switched. (If it's to constant battery +12V it won't turn off.) That may require an (extra) IGN +12V relay (with fuse) if existing sources can't handle the compressor current. FYI - the ON switch's dashed wiring to "+12V" was dashed for simplification. In its original form (ie, as per here; Reply #7) the ON switch's +12V could be from another source - eg, HU remote output or other enabling circuit. There are alternative circuits which IMO are more attractive if the additional 2nd relay is needed (I dislike using multiple relays for what I consider to be single relay circuits... or paraphrased, I prefer using solidstate circuitry for logic and leaving only using relays to handle the power switching), but that latching relay circuit is simple and suited for non-electronic DIY types. (FYI - I originally devised it for a water pump after only finding equivalent circuits that used totally unnecessary additional electronics!)

Thank you for your reply. I think that is what I was looking for. Floyd

Never mind. I didn't see the requirement ot turn it off with the IGN still on.

I think davep is doing my trick and confusing threads. Besides, turning off with IGN still on was/is not a requirement.