make gps tracker see engine runninng?

My company uses GPS tracking in all of their service vehicles. They're cellular based, so tracking is in real time using a website. They've all been wired up the same way - constant power and ignition to turn them on/off with the key. Pretty standard installs. Now, management has decided that they want to see when the truck is running, so they know when the tech is sitting at a site with the engine idling for two hours or whatever.... Can definitely see their concern when gas is $3.79 a gallon... The way they're wired up now they can't tell the difference between the truck running and idling or the tech having the key on with the radio playing.... The GPS units we have are equipped with 4 aux inputs for door triggers or what not. Where can I tap into that is only on when the vehicle is running? Alternator output? Fuel Pump? Ignition Coil?     Since it's an input, I don't think I would damage any of the above circuits by tapping in, but I probably would diode isolate just to be safe... I also thought about Tach like on a remote start, but those units are set up for the tach signal, whereas these GPS units have only (-) inputs. Any thoughts?

The alternator charge light is probably the best, but make sure the unit can handle a 12V-16V input - they might be a 5V input, or even GND switching. The alt light goes high (12V) when the engine is running and charging. Fuel pumps are controlled by the alternator else usually the ECU (if EFI). Ignition coils are tricky as they pulse up to 200-400V, though an RC circuit with voltage limiter is not too difficult - except for diesels (ha ha).

oldspark wrote: The alternator charge light is probably the best, but make sure the unit can handle a 12V-16V input - they might be a 5V input, or even GND switching.

The input is neg trigger. But I've never seen a vehicle with a charge light? Doesn't the light usually come on when there's a problem charging? Aren't most alternators these days combined with the voltage regulator/converter? I'm pretty sure that most alternators I've worked with (On Honda's at least) have one heavy gauge wire exiting and another smaller plug... I thought gone were the days of external voltage regulators, and the alternator converted AC to DC internally? I'm no mechanic though... Just a lowly 2 way radio equipment installer. :)

Alternators have had internal voltage regulators since the early 1980s (Lucas started circa 1976). Conversion of ac to dc has nothing to do with the regulator - that is done by diodes in the alternator. Yes - charge lights come on when there is a charging fault, but that is when the alternator's (regulator's) charge-light output (D+ or L etc) goes high (+12V). Like most traditional dash warning lights, the charge lamp is IGN +12V on one side and grounded on the other (when in a fault situation. To invert that signal, it's easiest to use a relay with 86 to alternator D+/L and 85 & 30 to GND and 87 to output. Then when the relay is energised (ie, engine is running so alternator charges and alt/reg charge-lamp output is +12V and charge light off), the output is switched to GND. (A pull up resistor may be required depending on the GPS inputs - typically 1k - 10k Ohms.) You have never seen a vehicle with a charge light? Amazing! But a charge light is actually a no-charge light - the same as an oil light is a no oil (pressure) light, etc. I take it you have seen no-charge lights? (Pun not intended - I am assuming you have seen "charge lights".)

Hmmm... Might be a bit of a challenge finding the charge light wire in the cluster, so I had an idea... What about tying one of the inputs to the starter wire? That way, when management runs their report or whatever it is they do, they'll see an activation on that particular input, which would be assigned a name like "crank" or "engine start", and they'll know that the time beyond that activation the engine was running... That might be easier? Just spitballing here trying to come up with a solution...

The problem with the starter trigger is that you can't tell when the engine is off. But the L (chargeLamp) wires shouldn't be hard to find. Locate the alternator. As you said, it has one heavy to the battery (B+ to +12V), and then smaller wires. Assuming it is not a newer EMS interactive alternator (DP etc types), it will probably have 1, 2, or 3 wires. A single wire is the D+ which is the same as the multi-wire L - ie, the chargeLight. 2 wires are usually S & L (aka SL types) where S is "Sense" and goes to the battery +12V (usually via a fuse) and L is the chlamp. (Hey - a new word to compliment my splugs, sparts & flinks (fuse-links). Thanks!). Older 2-wires can be IGN+12V (I or Ig) and L (aka IL types) 3 wires are usually IGN & S & L (aka SIL types).    They all have a charge lamp "terminal". [ FYI trivia: Traditional alternators required a trickle or tickle current into this terminal to ensure rotor magnetisation to initiate charging. The current came thru the charge lamp from IGN +12V - hence a broken or missing charge lamp could mean no charging. Later vehicles had other bulbs in parallel (eg, brakes, and EFI low fuel) that used the L circuit as a power-on test - as long as at least one was intact, the rotor would be tickled. Modern alternators may initiate else continue charging without the L-circuit trickle current. ] The alternator is probably the easiest place to tap into, else find the appropriate color-code for the L wire and then match to the dash wiring. Only one small wire need be pulled into the cabin (assuming that's where the GPS unit lives). The same would have to be done if sensing spark - unless the internal tacho wire is found. But spark/tacho requires a bit of circuitry. What sort of truck(s)? (Model & year.) It may be that a wiring diagram could be sourced etc. (Jap L's were often white-red.)    Else the alternator type - unless it's a single wire which means a D+.

There's no reason you couldn't use the actual ignition wire as the only time it should have power is if the motor is running. If your drivers are sitiing with the key in the on position and not running, well this is not good for the ignition system of the truck to start with. Don't the trucks have an accessory position for this?Mike M2

Tech Manager

CS Dealer Services

Mike M2 wrote: There's no reason you couldn't use the actual ignition wire as the only time it should have power is if the motor is running.

Man I feel so stupid! Yes, so obvious, and so simple. That's the stuff I always think of after seeing others' complex solutions! I realise know I saw the "when the engine is running... and went into auto-UIBI mode. (UIBI being the Ultimate Intelligence Battery Isolator - aka an L-controlled relay LOL!) I'd use IGN +12V since ACC could be used with engine off and listening to the radio etc. (Plus ACC suffers a break whilst cranking.) Thank you Mike!