7

I am working with a 1965 mustang and have added heated seats.

The seat heater wiring does not have a latching circuit and is controlled by a SPDT Hi/off/Low switch.

In an effort to only allow the seats to be powered when the engine is running, I've added a relay to the control wiring that will have a fused direct battery feed for the heat load and "running only" source for the relay coil.

I thought of using the feed off of the alternator "BAT" output. My problem is that this wire is terminated at the hot side of the starter relay with the positive battery feed, so the coil would be always energized.

To isolate the battery from the Alternator output I was thinking of adding a diode. Not being sure of the alternator currents, I do not know how to accurately size this diode, an I am concerned about the heat it would generate.

Is there maybe a better TAP that I can use for this? Maybe the "fld" or "sta" from the alternator or something off of the voltage regulator that would be a better?

Pᴀᴜʟsᴛᴇʀ2
  • 165,084
  • 32
  • 259
  • 508
TopDownCar
  • 73
  • 2

1 Answers1

1

I have two solutions for you, depending on your skill level.

The first is using a zener diode to turn on the relay once the voltage is above 12.6 volts. This will energize the relay anytime the battery voltage is above 12.6 volts. You could go as high as 13 volts, but that might turn the relay off under high electrical loads with the engine running. The 12 volt battery in the car tops off at 12.6 volts, so other than a surface charge the only time the voltage will be higher than that is when the alternator is running. I might would start off with a breakdown voltage of 12.8 and see how that works out for you.

Option two is to go with a commercial solution. Lind electronics make several shut down timers that you may like.

The T2 Shut down timer turns off after a preset time or voltage.

enter image description here

They have several other models you may like as well.

Move More Comments Link To Top
  • 18,788
  • 5
  • 54
  • 76