ok my temp guage must be wired wrong.
i have it grounded to the common ground and 12 volts is from either the cig lighter or cd player.

now my temp guage jumps 5 degrees when the ignition is truned to on from accessory, 5 degrees with my blower motor, and 7+ with my lights. so all together 12-15 deg higher than it should read when driving at night with the heater on. why is this, is there a better way to wire this guage up?

 

Welcome to the world of electrical supply / ground problems...


-Ted

 

What exactly is this "common ground" you used? Have you measured the voltage on the gauge's power wire when the change happens? Does it change too?

 

no i have not, its behind about an hours worth of crap moving, removal. is there one perfect place to tap to?

 

For power they're all as good as one another, as gauges draw very little current. For ground you don't tap into anything, you fix the wire to the chassis or to metal bolted to the chassis.

 

but non of this explains why my temp guage goes up when stuff is on, id expect the opposite

 

*sigh*
Then I think it's time you take a basic course in electronics and electricity?


-Ted

 

damnit reted, im sorry but if you know dont taunt me with it, just tell me and be done with it

 

Oh, you want the unabridged version?

Alrighty then...

Most electronic gauges use a simple thermistor as a sensor, and "reads" off voltage off the feedback.
This voltage is typically not regulated.
So, it's at the mercy of your electric and / or ground system.
You have fluctuations in either the electrical power or bad grounding, and the signal fluctuates like you seen.
My SPI water temp gauge does this - it changes up to 10F depending on electrical load.

Ensuring good grounds will minimize this phenomenon, but I doubt it will totally eliminate it.

So, short of stuffing a power regulator onto your gauges / sensors and running isolated wiring, you basically just gotta live with it.


-Ted