Lights off lower EGT's?!?

[shealy]

Recently noticed something with my EGT's. When I run the van with the headlights off, the temps seem to remain a bit lower. Also, when I stop driving the van, and am waiting for the EGT's to lower before shutting it down, it seems like the temperature drops faster when I turn off the headlights...

I can't seem to figure out why? I'm guessing it would have to do with the draw from the battery being less when the lights are on, but how that affects EGT's is beyond me.

Any thoughts?

-Steve

[yojimbo]

It doesnt alter the EGT's, but it does alter the behaviour of the sender/gauge combination. Since its unregulated the voltage with the headlights on is slightly lower than with them off, perhaps due to the way it works that equates to a higher reading on the gauge.

Alternatively, and this is silly, the load of the headlights on the alty loads the engine more and for any given speed the engine is working harder than for the headlights off.

The latter is ridiculous, although somewhat true, the lights on will load the engine, but not enough to lift EGT's I'd imagine.


I would suggest driving everywhere with your foot to the floor to keep the voltage up, and hence, the indicated EGT temps down.

[shealy]

Thanks, that seems to make sense in regards to the alternator loading the engine a bit more.

I would suggest driving everywhere with your foot to the floor to keep the voltage up, and hence, the indicated EGT temps down.

Is this a joke though, or is there some truth to this? Seems kinda counter-intuitive that putting the pedal to the floor would in turn relate to lower EGT's. Shouldn't it be the other way around?

[yojimbo]

Yeah I was kidding for that part

You'd need to measure the voltage running, with lights on and off to see if there was much of a difference, but usually if you have the engine running and switch the lights on you can hear the engine note change as the load on the alternator pulls on the motor.