Temperature sender/sensor... 7.3L

Sounds like you have air in the coolant system, some coolant systems have very specific bleed procedures after you open them up to replace components.

Ahhh....feels good to be buttered!

sounds more like the wiring is chaffed and causing issues with the sensor

Thanks BurbMan.
You are wonderful.
And very insightful.
And full of ... intelligence...

What about this theory.

Wrong part.
Same mechanical dimensions.
But more sensitive thermistor?

(Im assuming its some type of resistor inside)

Cant be chaffed wiring cuz it worked before.

But i was thinking possibly the contacts in the connector weren’t touching properly, but i am now doubting that.

I took a sewing pin and tried scratching/cleaning contacts and attempted to bend contact plates so as to touch male pins better. No difference.

The only way to nail this to the sender is to put a jumper resistor between the disconnector sender plug and chassis ground.

If the gauge needle still wanders then you definetly have a gauge, or g
Harness problem.

Get on a search engine to the aficionado's web page for your vehicle. Your mission will be to ask the resistance range of your sending unit.
You need to go to radio shack and buy a resistor halfway in between the high andow resistance extremes.

Typically, the vehicle manufacturer publishes a chart (usually in the Factory Service Manual) that shows how much resistance the sender is supposed to be producing at any particular temperature.

You look up that resistance on the chart, and then use an ohm meter to measure the actual resistance being produced by your sender.

If your measured resistance comes close to matching the resistance shown on the chart, you know that your sender is good - and that you problem is somewhere else.

LittleBill wrote:
sounds more like the wiring is chaffed and causing issues with the sensor

Second on a wire issue.. Hot/Cold one is shorted the other open.

Middle of the dial. that's when it is reading the sensor.

MEXICOWANDERER wrote:
You need to go to radio shack and buy a resistor halfway in between the high and low resistance extremes.

Mex you've been south of the border for too long, no more Radio Shacks.

I'm changing my diagnosis to wiring also. Air in the system will cause the gauge to go full hot when the air pocket hits the sensor area, but does not explain the gauge going to full cold after that.

At the same time, chafed wiring is not as likely on newer vehicles....I would replace the sender and see if that fixes it, they are fairly inexpensive.

BurbMan... you are already fully buttered. And my mom always told me it's a sin to waste butter.
But you beat me to it. That's the first thing I thought of when I saw the Radio Shack reference.

I watched it more carefully this morning.
At first key turn, with engine cold... the gauge was at 1/4 hot.
Then in about 5-7 minutes, it drifts up to full hot.

Then the red light comes on telling you to look at your gauges, something is wrong.

Then at some point un-noticed, the needle is back to full cold.

If this happens every day the same way, then how can this be a chaffed wiring issue?

Also, the temperature circuit worked fine when the old sender was good (granted it's been broke for about 6 months though).