erratic Temp gauge

[supercj]

Does anyone know what to replace to fix an erratic temperature gauge? Many thanks for anyone who can help.

 

[mawrazen]

It may not be the gauge. Please give us some more info on the phenomenon. Example :Stays on C then jumps to N in normal then back to C (Cold)

You can test the sender unit with a voltmeter.

 

[jm_vg]

May be the thermostat too. Check it !

 

[supercj]

the temp gauge will come up to the lower normal range but then it will run up higher fairly quickly then jump back to the lower normal range and stay there. Often times it will go down to cold and stay for a little bit then jump back to normal—overall it moves all over but mainly stays in the bottom area, and averages out in the lower normal range.

I'm pretty sure it is not the thermostat because that is new as it was replaced just this last winter. Thanks for the reply but anymore knowledge would be greatly appreciated!

 

[seth247]

the water temp sender is on top of the engine block to the right of the alternator and to the left of the throttle body. Kinds hidden down in there but you can see it.

Check and clean the connection to see if that helps.

 

[Maniak]

the water temp sender is on top of the engine block to the right of the alternator and to the left of the throttle body. Kinds hidden down in there but you can see it.

Check and clean the connection to see if that helps.

Also, its the one with a single wire.. The one with multiple wires about the same place is for the computer.. The 2nd wire one is for the gauge..

~Mark

 

[mawrazen]

Aftermarket Temp Guage can replace questionable stock unit

I would try flushing the cooling system and adding Fresh Radiator fluid.

I also have installed an auxilary electric fan and aux tranny cooler in front of the radiator to keep the temperature down .(for towing)

An aftermarket temperature gauge is available if you cannot troubleshoot (repair) the stock gauge or sending unit.

Cost, < $50

Not worrying about your temp gauge, Priceless

Good Luck!

 

[shaggymane]

Tornado alley huh? Must be a little left of were I live.

Does your gauge act like this on the hiway or mostly in stop and go driving?
If your fan is not coming on it'll heat up till the thermostat opens, then show a drop in temp as cooler water begins to flow through the engine.

 

[supercj]

Tornado alley huh? Must be a little left of were I live.

Does your gauge act like this on the hiway or mostly in stop and go driving?
If your fan is not coming on it'll heat up till the thermostat opens, then show a drop in temp as cooler water begins to flow through the engine.

...it acts like this all the time, stop and go and cruising down the highway. I don't have an electric fan so your statement about the fan isn't relevant. I will try cleaning the connection to the temp sensor but otherwise I just want to know what to replace so that it will work properly.

thanks for the input!

 

[Alan_V]

...it acts like this all the time, stop and go and cruising down the highway. I don't have an electric fan so your statement about the fan isn't relevant. I will try cleaning the connection to the temp sensor but otherwise I just want to know what to replace so that it will work properly.

thanks for the input!

Doesn't sound like a mechanical issu. Sounds electrical.

Go to the temp sending unit (the one wire type). Backprobe the connector using a heavy duty pin (like for sewing). Stick the pin sown the wire at the connector and then read the voltage between the pin and ground. If the voltage is jumping along with the gauge, it's the sending unit. If not, the next thing to do is backprobe at the gauge connector. If it's still not jumping it's the gauge, if it is, it's in the harness or at an intermediate connector.

 

[supercj]

Doesn't sound like a mechanical issu. Sounds electrical.

Go to the temp sending unit (the one wire type). Backprobe the connector using a heavy duty pin (like for sewing). Stick the pin sown the wire at the connector and then read the voltage between the pin and ground. If the voltage is jumping along with the gauge, it's the sending unit. If not, the next thing to do is backprobe at the gauge connector. If it's still not jumping it's the gauge, if it is, it's in the harness or at an intermediate connector.

...uh, just wanted to check to make sure, do I need to start the engine to do this or not? lol

 

[Alan_V]

...uh, just wanted to check to make sure, do I need to start the engine to do this or not? lol

Yes, unless it will do it key on, engine off. Your looking to compare what's on the gauge to the voltage displayed on the meter.

If you need to drive it to get it to happen, you'll need to make a lead using some wire long enough to get it to the sender then to your volt meter. Oh yeah, get someone to go with you, one to drive and one to watch the voltmeter.

 

[MrShorty]

Things I have done to diagnose and fix erratic temp gauges:

1) As noted above, the PCM uses a separate sensor than the one that drives the dash gauge. I've backprobed the ECT sensor with a voltmeter to measure the voltage drop across the sensor and test drove. If the ECT signal parallels the dash gauge, then the problem is likely in the cooling system. If the ECT signal is steady, then there's a problem in the dash gauge sender circuit.

2) On one occasion, my erratic temperature was caused by a clogged heater core. Backflushed the heater core and all was well again.

3) On another occasion, my thermostat was sticky. It would stick closed until it got hot, then open and stick open until it had overcooled. On that occasion, the t-stat was less than a year old when it started.

 

[ricklee4570]

Here is what mine does. Upon first start up of the day it will slowly start to climb up, which is normal. Then it continues to climb until it is about 3/4 of the way across the dial. (Normal but a little hotter than I would like) Then all of a sudden in rapidly drops to the left (cooling). It will then climb again until just past the middle, then drop and finally even out to normal temperature.

My mechanic said it is normal. He said that as the engine is warming up, the temp starts to rise. The guage is monitoring the temps. When it gets fully warmed to the point to where the thrmostat is to open, there is a slight delay. The delay is the time it takes for the thermostat to open, and the water to flow past it, and finally the cooler water to get to the temperature sensor. By then, the temp is showing higher on the guage. Then when the cold coolant hits the sendor, it goes lower. Meanwhile the thermostat is starting to close due to the cooler water circulation and it is slightly restricting flow. As you drive this pendulum effect starts to even out and minimalize. Eventually settling in to a stable normal temp.

Whew! I guess this sounds plausible!

 

[customchrome36]

i can not find the temp sender for the gauge. i have the new sender but i cant find where it goes...the only one i can find is the one for the computer...i talked to my mechanic and he said it was in the head on the drivers side in the back but the only one there is the oil pressure sensor...please help i got this truck in may and still cant find the thing

 

[seth247]

Oil press for the 4.0 is at the front near the timing cover.

The temp guage sender should be in the front of the lower intake manifold underneathe the throttle body and stuff. It has only one wire and the terminal on it looks like the thread end of a bolt.

 

[Maniak]

i can not find the temp sender for the gauge. i have the new sender but i cant find where it goes...the only one i can find is the one for the computer...i talked to my mechanic and he said it was in the head on the drivers side in the back but the only one there is the oil pressure sensor...please help i got this truck in may and still cant find the thing

Are you looking at a 4.0 ohv motor? or something else?

On the OHV 4.0, the coolant temp sensor for the gauge is on the intake manifold, near the front..

The oil pressure sending unit is on the side of the block, drivers side, right in front of the motor mount.. practically behind the power steering pump.

~Mark

 

[customchrome36]

no its a 2.3 inline 4

 

[Currency]

Here is what mine does. Upon first start up of the day it will slowly start to climb up, which is normal. Then it continues to climb until it is about 3/4 of the way across the dial. (Normal but a little hotter than I would like) Then all of a sudden in rapidly drops to the left (cooling). It will then climb again until just past the middle, then drop and finally even out to normal temperature.

My mechanic said it is normal. He said that as the engine is warming up, the temp starts to rise. The guage is monitoring the temps. When it gets fully warmed to the point to where the thrmostat is to open, there is a slight delay. The delay is the time it takes for the thermostat to open, and the water to flow past it, and finally the cooler water to get to the temperature sensor. By then, the temp is showing higher on the guage. Then when the cold coolant hits the sendor, it goes lower. Meanwhile the thermostat is starting to close due to the cooler water circulation and it is slightly restricting flow. As you drive this pendulum effect starts to even out and minimalize. Eventually settling in to a stable normal temp.

Whew! I guess this sounds plausible!

I have a few minor leaks on my radiator but I've never seen mine go past the N in Normal. Now that it's colder outside it never reaches the N in Normal.

I did see a stream of anti-freeze running from the back side of my radiator a few days ago. But then it stopped and has not done it since then. I've been and will continue watching it. My explorer was not running when I seen the leak and puddle. Maybe my explorer doesn't run hot or had at some point been taken care of. I know the previous owner couldn't properly maintain it.