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92 Temp gauge stuck on cold??? ECT??

41K views 28 replies 13 participants last post by  schufflerbot 
#1 ·
My temp gauge is stuck at cold no matter how long I drive. I have driven over 2 hours and it is still stuck at cold. Yesterday I took a test light and plugged it into to wire that goes to the coolant temp sensor and it went up on the gauge in my dash. So I assumed it was the coolant temp sensor (the one next to the distributor) So I replaced it, well this did not fix my problem.

The other day when I had the tubes that connect to the air box off of the throttle body, I seen that my ECT sensor was broken....the one with the two prongs.... It was not even connected. So I connected it but it is just hanging on there and I dont think it is really working right. Sometimes when I start it it takes a real long time to fire up.....so here is my question......

Would a bad ect sensor cause this? Do I need a new thermostat? I know I need a new fan clutch because it is sloppy. But if i needed a new thermostat wouldent it be stuck at high?? Any help would be appreciated thank you in advance...
 
#2 · (Edited)
Did you/have you pulled codes? Having the ECT unplugged will give you a code, but not a CEL if I remember correctly.
Maybe you got a bad temp sensor, as your gauge works. You can test the new temp (dash temp) sensor with a soldering iron, plug in the sensor (one wire), and heat it (the end that goes into the manifold water passage), also ground the sender (a jumper cable on the threads will work) if the dash gauge works when you used a test light or when you ground it, but not when installed, the dash gauge and the wiring to it should be good.
Did you use a bunch of thread tape on the threads? The sender gets it ground through it's threads. Don't overtighten it, it has tapered threads, the tighter it gets, the bigger it gets, until you overtighten it and crack the intake manifold.
 
#5 ·
The other day when I had the tubes that connect to the air box off of the throttle body, I seen that my ECT sensor was broken....the one with the two prongs.... It was not even connected. So I connected it but it is just hanging on there and I dont think it is really working right.
start off fixing the things that you know are broke. I would fix the ect connector and change out the ect sensor as well while your in there.
 
#6 ·
X2 ^

The ECT = engine cooling temp sensor http://www.oreillyauto.com/site/c/d...nsor_1106031_3034&keyword=engine+temp+sensor+ is a fuel manager at cold start and normal operation so any isssues with it could actually prevent starting, you'll notice the harness side connector "unsnaps" and comes apart like an Off Road weather pack style so you can either go to the JY and find one el cheapo or buy a pigtail at the auto store for a bit more $$$, unsnap and resnap assuming there's no damage to the wries leads. http://www.oreillyauto.com/site/c/d...nsor_1106031_3034&keyword=engine+temp+sensor+

If you replaced the "brass style" http://www.oreillyauto.com/site/c/d...nsor_1106031_3034&keyword=engine+temp+sensor+ temp guage sending unit and it the needle is still off then it's either a voltage issues thru the lead wire or the dash gauge is fubar which can be replaced with a mechanical gauge for better accuracy....

After running the engine, the top radiator hose should be hot indicating the thermostat is working correctly otherwise it's either in backwards or fubar and if replaced get the correct OEM degree, mine's a 195* and make sure the radiator cap is also in good shape...



Good Luck ~ :thumbup
 
#7 ·
A '92 Bronco has two (2) coolant temp sensors- one for the computer, and one for the gauge.

The sensor for the computer has two wires, one green and red, the other gray and red.

The sensor for the gauge is a single wire, colored red and white.

If you take the wire off of the gauge sensor and ground it (the wire, not the sensor)- which is what you did with the test light, if you had it hooked to a ground- the gauge should move to its max hot reading. If it does, the circuit and gauge should be fine. Check the ground at the sensor body by doing a voltage drop test to the battery. It should read "0.00", or pretty damn close. You may have a bad sensor out of the box; it happens more than you might think.

If I remember correctly, temp does not effect fuel trim until the vehicle is in closed-loop, but I would still fix that two-wire sensor and connector that's broken, anyway. Temp is one of the biggest inputs for fuel trim, and with that sensor disconnected your gas mileage is probably in the toilet.

Oh, and my wife is from Appleton, too.

:thumbup
 
#9 ·
I appreciate all of your help.. APPLETON in the house!

The top coolant hose gets hot. When I tested the wire for the temp sensor it didnt MAX out the gauge it just brought it to about half way. I guess I will fix the ect sensor and see where I am at.

Thank you so much everybody. I truly love this forum.
 
#12 ·
I appreciate all of your help.. APPLETON in the house!

The top coolant hose gets hot. When I tested the wire for the temp sensor it didnt MAX out the gauge it just brought it to about half way. I guess I will fix the ect sensor and see where I am at.

Thank you so much everybody. I truly love this forum.
If the gauge only went to half with a good ground on the wire, the problem isn't with the sensor, it's with the circuit and/or the gauge itself. That gauge should be pegged to the hot side with that wire grounded.
 
#15 ·
necromancing this thread as i'm having the same issue. can someone point out where the ECT sensor is? i replaced the coolant temp sensor (the one near the distributor) and it didn't change anything. my dash gauge will move ever so slightly (maybe a millimeter) when engine is at operating temperature but won't go above that. setting the heater on full heat and 'vent' blows hot air, so i'm assuming the engine temp is where it should be.

is the dash gauge going out a common issue?

FYI - mine is a 1992 with the 5.0

thanks in advance!
 
#16 · (Edited)
necromancing this thread as i'm having the same issue. can someone point out where the ECT sensor is?
The ECT sensor is located above the thermostat housing on the intake. However, this has nothing to do with your gauge problem. Ground out the wire to the sendor near the distributor and see if the gauge pegs hot. If it does not, your gauge is at fault.
 
#17 ·
The ECT Sensor has nothing to do with your dash gauge, the single wire Engine Coolant Temperature "Sender" does. With the Key On-Engine off, remove the single wire and touch it to ground. If the gauge pegs to the right, replace the "Sender". If it does not, replace the gauge.










 
#21 ·
well, that was easy! gauge pegged to the right immediately, will be replacing the ECT sender tomorrow morning! woohoo!!!

y'all rock.
You want to replace the Temp Sender, not the ECT. As stated above the ECT tells the PCM (engine computer) the coolant temperature. The Temp Sender only operates the gauge on the dash.
IIRC, the ECT has two tweminals, the Temp Sender only has one.
One other caution on replacing the Temp Sender. The Temp Sender has a tapered pipe thread, that means that the the tighter it gets, the larger it gets. If you overtighten the Temp Sender you can crack the intake manifold (just ask JKossarides!). The Temp Sender also gets its ground from the thread on the sender. Too much teflon tape will insulate it from the manifold, and with no ground, the gauge won't work.
So, don't overtighten it, and don't put too much teflon tape on it.
 
#23 ·
Replaced the temp sender after the 'ground it out' test came back positive. (meaning, the gauge on dash read full hot when i ground out the wire that connects to the temp sender.)

I still have nothing on the dash, it's pegged to full 'cold' and when the engine has been idling for about 10 minutes, the temp gauge on the dash has nudged up just a hair... still not even reaching the 'cold' line.

i tested for ground with the multi meter and the top of the post on the temp sender is reading good ground... im stumped.

any ideas?
 
#24 ·
When I first got my bronco I noticed that the temp gauge would never seem to move much. I replaced the sender, checked the wiring, everything was working, just not much activity with the temp gauge. Then about a week later my water pump went out. Thats when I discovered the PO removed the thermostat completely. Once I put in the correct thermostat and got a new water pump on it, everything worked perfectly.
 
#28 ·
Its just really hard to get the inside thermostat housing bolt off. No normal wrench will fit. I had my mechanic do it and I never saw what he used.

some have modified a box wrench like this to help get it off.




If I ever take it off again, im getting one of these to replace it.

 
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