ok.. got up this morning and got ready to go out and do some stuff around town. it was .. id say about 45deg out this mornin.. got in the ram and started it up... shift it into neutral like i always do and let it sit for about 2 mins to warm up before i start to drive... warmed up a bit..put it in reverse and started to drive. about a min latter the temp gauge shot straight up to the red and the check gauges light came on. got scared..turned right around got back home and shut it down... shut it off let it sit for about 5 mins and then started it back up... for about 10 seconds the temp gauge read noraml then shot straight back to the red... did this like 4 or 5 times.. got the hanyes out and looked it over. thought it was the the thermostat so i felt the upper radiator hose and its warm to hot .. so i know the thermo is open to allow coolant to go through..i felt the lower radiator hose and its ALOt cooler so i know the colder fluid is geting into the engine. its not running crappy at all .. runs fine. the coolant level is great too.. i put it into to neutral and ran it about 2500 rpm for about 3 mins and no change. and disconnected the battry for about 10 mins and hooked it back up and no change. any idea fellas? also when the engine cooled down i felt the radiator and it was cool... started itup and a litle bit later it got warm to hot so i know the hot fluid is getting into the radiator and the cooler fluid is getting into the engine. and this has never done this before...i drove around yesterday for a total of about 2 hours and everything was great.. now today it all changed .. and ideas?

 

yes, you have a short on your ECT sensor (coolant temp) or the wiring. your ECT will have a resistance that is very high when the coolant temp is low, as it heats up the resistance drops, yours apears to be shorted in some way, either the wiring or the sensor is shorted. pull the ECT plug and short the 2 wires and you'll see your guage go to full max on the dash... then you can ohm it out to find out if it's your wiring or the sensor... my bet is the sensor.

 

hey steve..how ya been? thanks for the advice... on my way out to check it now... thats something that could go oever nght? the ECT is in the haynes?
thannks again!

 

been busy working on the wifes Dakota, put some edlebrock IAS shocks on it this past weekend and some PowerStop cross drilled rotors and pads last week. she is a happy woman right now. but back to your problem, yes, the ect can go bad at anytime, it's just like any other part, they dont last forever. check for a short on the sensor 1st, make sure your guage is showing you the motor is over heated 1st. or you can yank the sensor and plug the hole by stuffing a rag into it and test the sensor on the stove in a pot of water.

the good thing is you know your motor is not overheating...

 

yea... as soon as i realized the motor is running fine.. i hooked everything back up and returned to my long list of things i gotta get done on the day off... went to autozone and got the sensor.. 11 bux.. looks REALLY easy to change out... wierd thing is .. according to haynes i have the ect sensor that it located and is for the diesel engines... either way i got a new one..just got home bout to eat dinner and waiting for the truck to cool down and ill go out later this evening to swap it out .. now if its still messed up ill know its the wiring witch doesnt look to fun b/c it seems to run along with a larger harness slong the fuel rail and down towards the tranny.. iether way ill do the same as always post my findings for others later

 

FIXED!!! 11$ sensor and them temp gauge is back to normal... really easy to fix and inexpensive@!!!!!!!!!! runnin like a champ now... THANKS steve!!!! saved me again!

 

your welcome! happy to hear it's fixed!

 

I have a very similar problem.

1998 quad cab, This morning temp gauge shoots up check gauge lights come on and heater blowing cold air. Gauge temp drops down heater blowing hot air. This repeats about three times in about a 7 minute ride. I assumed it was the thermostat sticking (opening and closing) because the heater would get hot and cold at exactly the same time.

I was going to run to autozone get a manual and a thermostat. I don't think a faulty ETC would produce this because I assume the ETC is just reporting the temp and not controling the opening and closing of the thermostat which I assume is just a mechanical thermostat.

What do you think?

 

yea the t-stat is mechanical so any electronic readings your getting would be cuased by faulty sensors... make sure you get the correct ECT sensor... they first gave me one for a desiel and the temp gauge did the exact opposite (gauge would always read below 130) untill i got a new one that looked a little different then the one i buught first... swap the stat .. you should be 5.0