Coolant Gauge Electrical Problem !!!!HELP!!!

[Timo]

Problem

Electrical Gauge reading between 200F to 250 F. Engine at 180F


What I have done so far and still not fixed.

Replaced Thermostat
Replaced Sending unit 287.4ohms to -22.7ohms 12v
Replaced Gauge 287.4ohms to -22.7ohms 12v
Run new wire from sender to gauge.
Sanded all ground connection on frame and engine

When I attache the MultiMeter to signal wire and ground it shows the correct ohms.
I attach the Signal Wire to the gauge it will drop 100 ohms to like 20 to 60. thats like 200f - 250f

Losing it, probably switching to mechanical coolant temp gauge\

Thanks Timo

[j.miller]

Well, Brother, You're in San Antonio.....Maybe the guage is giving you the "Feels Like" factor....I know that doesn't help but just trying to lighten your mood. You have replaced all the (not so) moving parts.....unless, maybe, did you use teflon tape on the sending unit....is it one wire or two ?...da bat

[Timo]

no Teflon used.

should there be voltage between the signal wire and ground, says 4 volts.111288

sorry wrong picture

[Big Blocker]

Quote: "Replaced Sending unit 287.4ohms to -22.7ohms 12v Replaced Gauge 287.4ohms to -22.7ohms 12v"

Curious. just how do you measure -22.7 ohms??? resistance is resistance, there are no negative values in ohms that I'm aware of . . . no resistance = 0, anything that can create resistance will show as a positive number.

I'm thinking you have a mis-watch somewhere between the sensor (which is grounded) and the gauge. OR you are taking ohm measurements at the wrong place.

Also, How are you verifying that the engine is at 180°f ??

Doc

[Timo]

i meant 287.4 to 22.7

taking the reading of the coolant with a laser temp measure

[CraigS]

Assuming the sensor is the brass thing just behind the T-stat housing I see it's one wire. W/ key on, take the wire off the sensor and touch it to the engine ground which should send the gauge to it's max reading. I have never tested for V in the sensor wire but it seems there could be some coming from the gauge.

[RBachman]

How is the backlight connected? Could that cause this?

[Timo]

found the problem, bad ground cable from gauges to ground. now everything works

[Avalanche325]

found the problem, bad ground cable from gauges to ground. now everything works

Bad ground. That seems to be the answer for 95% of gauge problems. Glad you found it.