Coolent Temp Gauge not testing to full spike

[Faeble]

Hey everyone. I am new here but i have my first f250 1992 7.3 idi and its a beat up horse but drives strong and runs great however there are a few electrical things i am baffled about.

My gauge... I thought it wasnt working... so i replaced one coolent senser and came to find out after testing the sensers that they both work. The wiring is hot too... i never seem to overheat but the gauge always stays below center and drops all the way down comming down from a long uphill grade.

When i use my test light to see if the actual coolent temp gauge cluster works when i turn the key to on... the gauge goes only to the first letter after the bottom line.

Usually when you run the test light to the gauge wire and turn the key to on with the other end of the test light beibg hooked up to battery the gauge should spike all the way to hot no?

Anyone habe any ideas on how to trouble shoot this. And does anyome have any advice to offer?

I just really need to know my temp gauge readi gs as i am constantly towing.

Cheers and thanks in advance!
Faeble

 

[SebastIDIan]

The only time I see mine move past the N is when I pull a 40k hay wagon in 1st longer than a mile.

 

[franklin2]

The way the gauge works, it's supplied power all the time the key is on, the single wire going to the sensor is ground. The sensor varies the ground on this wire, which makes the needle move.

So to test the gauge and the wire to the sensor, turn the key on(engine can be off) take the wire off the sensor and let it hang in the air touching nothing. The gauge should swing full scale low or high(can't remember which). Then take the wire and put it on a good ground on the engine, the gauge should swing full scale the opposite way. If it passes this test, the gauge and the wiring are good.

Are you using any thread tape or some other type of sealer on your sensor threads? If you are, this could be interfering with the grounding through the threads. If you use any sealer, use it very sparingly on just a few threads up high on the sensor.

 

[Hydro-idi]

These stock temperature gauges are absolutely useless. Even when they are working properly, who knows what the true engine temp actually is. Just above the N, or right below the R? Doesn't tell anyone didly squat really.
Get yourself a real temperature gauge and hook it up. They are cheap & easy to install.

 

[gandalf]

I have to agree with the above poster. The temp gauge in our truck is just a moving idiot light. There is no calibration, and little consistency from one truck to another. The best you can hope for is relative temp from one time to the next. "Well, it seems to be running a bit cooler than it did yesterday." Your best bet, buy an aftermarket gauge for temp, oil pressure, trans temp (if you have an E4OD).

 

[BrianX128]

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Yeah check this video I made a while back out. You would think my oil pressure was fluctuating and the engine was cold, but the oil pressure was at a solid 40 and the water temp was at 180 steady.

Sometimes the factory gauges work, sometimes they do weird crap for no reason. Either way they really don't tell you anything worthwhile unless you've already *****'d your truck usually.

 

[Faeble]

The way the gauge works, it's supplied power all the time the key is on, the single wire going to the sensor is ground. The sensor varies the ground on this wire, which makes the needle move.

So to test the gauge and the wire to the sensor, turn the key on(engine can be off) take the wire off the sensor and let it hang in the air touching nothing. The gauge should swing full scale low or high(can't remember which). Then take the wire and put it on a good ground on the engine, the gauge should swing full scale the opposite way. If it passes this test, the gauge and the wiring are good.

Are you using any thread tape or some other type of sealer on your sensor threads? If you are, this could be interfering with the grounding through the threads. If you use any sealer, use it very sparingly on just a few threads up high on the sensor.

Thank you all for responding.

To answer the above qoute first...
I have tested the wire with the test light and gator clip to the battery and the needle only runs a qaurter up to the N of Normal. It doesnt swing to the highest point (hot).

I didnt use any cielent as i was told the ceilent isnt needed. So it is weird because when i drive the temp does work but a mechanic buddy said because it swings up past the C and then the bottom line and then will go up to the N (normal) and sometimes a little past that when driving just know that if the gauge goes up to the N you are most likely overheating and need to pull over..the only tging is when i drive and it goes that high there has been no signs of overheating besides that gauge.... So does the mean the coolent temp cluster is bad or is there a way to adjust it if so?

 

[icanfixall]

Welcome to the forum. Our dash gauge works by two senders. The small sender found on the front drivers side of the block near the injection pump gear housing tells the gauge the temp to record. the large sender in the drivers side front head is the coolant over temp sender. It will close creating a ground and that will cause the dash gauge to swing way past the "L" in normal. So to test this just remove the wire to the large sender and ground it but have the ignition on and engine off. The actual test temp of the engine means nothing for this test.It works warmed up or ice cold.
And finally this dash gauge really tells us nothing. Yes... you can see where the temp is going but nothing tells you what the o or the m or any other letter translates in to actual coolant temps.

 

[Faeble]

Welcome to the forum. Our dash gauge works by two senders. The small sender found on the front drivers side of the block near the injection pump gear housing tells the gauge the temp to record. the large sender in the drivers side front head is the coolant over temp sender. It will close creating a ground and that will cause the dash gauge to swing way past the "L" in normal. So to test this just remove the wire to the large sender and ground it but have the ignition on and engine off. The actual test temp of the engine means nothing for this test.It works warmed up or ice cold.
And finally this dash gauge really tells us nothing. Yes... you can see where the temp is going but nothing tells you what the o or the m or any other letter translates in to actual coolant temps.

Ok. I will try that as well and thank you.

So then my next question would be if everyone is suggesting putting in a mechanical temp gauge...where would you run the tube and senser through the fire wall? Do i need to drill another hole? Also, the wich screw hole would you all put your coolent temp mechanical senser into on the engine. ?Any thoughts ?

 

[BrianX128]

Ok. I will try that as well and thank you.

So then my next question would be if everyone is suggesting putting in a mechanical temp gauge...where would you run the tube and senser through the fire wall? Do i need to drill another hole? Also, the wich screw hole would you all put your coolent temp mechanical senser into on the engine. ?Any thoughts ?

Under the ac condenser if you have ac is where the overtemp sender is. My picture is close up but that's the drivers side valve cover to help you figure out where I'm looking at.

Up by the ebrake there is a rubber grommet I drilled a hole in and ran all my sender wires through there.

You must be registered for see images attach

 

[Faeble]

Under the ac condenser if you have ac is where the overtemp sender is. My picture is close up but that's the drivers side valve cover to help you figure out where I'm looking at.

Up by the ebrake there is a rubber grommet I drilled a hole in and ran all my sender wires through there.

You must be registered for see images attach

Yes thats the one i have too.

I will buy a mechanical gauge today and try and install it. I had a hell of a time trying last time because of the angle and the tube being in the way. So i was hoping i could fix the cluster gauge .. but after talking to folks sounds like the temp coolent mechanical senser is the realest reading.

 

[Macrobb]

You can always go with an aftermarket digital/electrically-driven gauge. I've used one for years.
Obviously, though, because it is an electrical device, you want to run 2 wires from your gauge to your sender - one for the sender, and the other attaching ground to the ground on the sender.
Because an electrical gauge works on resistance, if the grounds aren't properly grounded, you'll get odd readings. This is also why the factory gauges do weird stuff(though they aren't calibrated in the first place).

Personally, I used a mechanical gauge for a few months(a relatively cheap one), and it never read high enough. I knew that the thermostat opens and maintains a 180-190F reading, and my digital gauges matched that... but the mechanical one I got never got above 170F or so. It was just off. Also, really slow to read.
My digital gauge I could watch the temps slowly fluctuate as the thermostat opens and closes, as well as see spikes when I floored it. The mechanical one has so much inertia it never showed me anything.

 

[Faeble]

You can always go with an aftermarket digital/electrically-driven gauge. I've used one for years.
Obviously, though, because it is an electrical device, you want to run 2 wires from your gauge to your sender - one for the sender, and the other attaching ground to the ground on the sender.
Because an electrical gauge works on resistance, if the grounds aren't properly grounded, you'll get odd readings. This is also why the factory gauges do weird stuff(though they aren't calibrated in the first place).

Personally, I used a mechanical gauge for a few months(a relatively cheap one), and it never read high enough. I knew that the thermostat opens and maintains a 180-190F reading, and my digital gauges matched that... but the mechanical one I got never got above 170F or so. It was just off. Also, really slow to read.
My digital gauge I could watch the temps slowly fluctuate as the thermostat opens and closes, as well as see spikes when I floored it. The mechanical one has so much inertia it never showed me anything.

Thats interesting
Could you give me the brand name and was sold as a package with a screw and wiring?

Thanks!

 

[Macrobb]

Thats interesting
Could you give me the brand name and was sold as a package with a screw and wiring?

Thanks!

I've used two different gauges:
First, was this cheap chinese gauge - $20: http://www.ebay.com/itm/2-52mm-Car-...Fahrenheit-F-LED-Gauge-Meter-US-/182396991945
I've not had any issue with them, except that the sensor is a bit weak mechanically. By that I mean: Don't overtighten the sensor into your adapter. Don't overtighten the nut on top where you connect your wire.

The only downside to this gauge is that replacement sensors aren't available. And they only read from 104F upwards, so you can't see the temps until it starts warming up.


Then, I got a more 'standard' sensor and gauge combo - a PT100-spec sensor and digital readout:
http://www.ebay.com/itm/RTD-Pt100-1...943924?hash=item41b9d9f7b4:g:ztEAAOSwa~BYUORL - sensor, $7.69
12V DC meter: http://www.ebay.com/itm/Digital-DC-...100-Temperature-Sensors-12VDC-F-/251281000159 - $10.99

You can find other gauges, meters and such that work, as long as it's compatible with the PT100 spec.

I installed this setup, and after getting it wired up, I really like it.
The PT100 spec uses two wires that both go back to the gauge, so you don't need to worry about grounding. You can get replacement sensors and gauges when you manage to destroy them. And, it seems pretty accurate. Really nice being able to turn the key on and see that the block is currently at 45F, and watch as it warms up from dead cold.

 

[MtnHaul]

As others have mentioned a mechanical coolant temp gauge is a great addition. I really enjoy being able to monitor coolant temps when pushing hard up a grade. If you decide to purchase a gauge I highly suggest you boil a pot of water and drop the gauge's probe into it being careful to keep it suspended in the water and not touching the pot. Water boils at 212F degrees at sea level, and for every 500 feet in elevation gain the boiling point drops by 1 degree F, so it should be easy to see if your gauge reads correctly.