Tripping a relay while engine/alt are running

[mike938]

Does anyone know of a way to have a relay going only when the car is actually running? In my car (97 camry) I am unable to find any fuses that are live only when the car is actually on but instead they all come on when the key is switched to on.

This was my attempt at creating such a thing however when tested it did not work properly. To test: I used batteries as the fuses with the starter fuse as a battery switched with a lightbulb after the switch before the diode so I could easily see that the starter is switched on. The remote turn on wire was also a lightbulb so I could easily see what was happening. Anything needing a ground (batteries and bulb on the Remote wire) were attached to a common ground.

The problem with my test circuit is that whenever the ignition (on whenever car key is switched to On in car) battery was attached the starter bulb wouldn't come on when the switch was on even though it would still trip the relay and turn the remote on bulb on. When the starter was turned off the Remote bulb would stay on (like it should) while the ignition fuse battery was connected and would shut off when the battery was removed. Also like it should, if the ignition battery was reconnected, until the starter switch was turned on the Remote bulb wouldn't turn on. When the starter switch was on and the ignition battery was not connected the light between the starter switch and the diode on that line would light up.

Does anyone know what I should use or what is wrong in my circuit?

Thanks~

Click to read more...

 

[phyphoestilic 5,000+ posts]

http://www.ehow.com/how_8450_relay-car-electronics.html

 

[mike938]

The problem with that (at least how I see it), is it will turn on my amp when I switch the car to "On" even if the car is not actually started.

Thanks for the quick reply though.

Edit:

Exactly what I want to do it have the remote turn on wire live once the car is actually started (starter gets power) until the car is shut off.

My example circuit turns the relay on once the starter is engaged and then draws power from a different fuse to power the remote turn on wire as well as using diodes to keep the 2 fuses isolated and using the ignition fuse wire to keep the relay tripped on.