Temperature gauge needle position ?

[CaptonZap]

Howdy all,
I used the search function and could not find an answer, so figured that a question here might be tolerated.
I just replaced the thermostat and gauge temp sensor, got most of the air out of the top hose, took it for a test drive, and noticed that the needle does not get above the bottom line of the arc on the gauge.
This is a 95 Ranger 4X4, 3.0 engine.The reason for the replacement was because I thought the thermostat was broken, since the gauge didn't go up.
The question is, where should the needle be when the temp is 195 deg at the thermostat housing, as measured with an infra red non contact thermometer?
And does the ECM use that reading to control mixture? I have noticed a decrease in mileage the last half year. This has an OBD1 system.
Thanks for any input.
CZ

 

[EricNobody]

My 90 ranger 2.3 is really cold blooded, even after an hour of driving, its only at "1/4" temperature. Nature of the beasts from my exp, might not explain laying flat, but if its just not making full temp, that's how it is for most of us





Sent from my RM-917_nam_usa_100 using Tapatalk

 

[RonD]

Most auto makers set 220degF as 1/2 on a dashboard temp gauge, Ford does as well.

So just below 1/2 would be normal operating range, 200-210degF

ECT sensor is a separate sensor usually located near the "sender" used for the dash board Temp gauge.
Sender is a 1 wire unit
ECT sensor has 2 wires, ECT is used by computer to determine if engine is cold, so needs to run rich, or warm, run lean using O2 sensors.

Neither of these "control the temp", they just report it.

If new t-stat(192-195degF) is working then upper rad hose should stay cold for a few minutes after start up, when coolant in upper engine reaches 195degF the t-stat should start to open and upper rad hose should start to warm up.
If upper rad hose starts to warm up with the engine, no delay, then t-stat is passing coolant, could be a bad seal or bad t-stat.

 

[CaptonZap]

Most auto makers set 220degF as 1/2 on a dashboard temp gauge, Ford does as well.

So just below 1/2 would be normal operating range, 200-210degF

ECT sensor is a separate sensor usually located near the "sender" used for the dash board Temp gauge.
Sender is a 1 wire unit
ECT sensor has 2 wires, ECT is used by computer to determine if engine is cold, so needs to run rich, or warm, run lean using O2 sensors.

.

Thanks for the input Ron,

I didn't see a two wire sensor near the gauge sending unit, but I will look for one tomorrow.
Is there a way to test the two wire unit for function while it is in place?
(voltage, resistance?)
CZ

 

[FritzTKatt]

KOEO should give 12v to one of the wires. (Don't ask me the spec) You can test resistance of the sensor itself though. You may have to hit the sensor with the laser thermometer to reference the resistance to the temp to make sure it's in spec.

 

[kimcrwbr1]

To check the temp guage run a jumper wire from the temp sender 1 wire to a good ground and turn the key on. If the guage reads hot the guage is good. As far as performance issues you will need to pull the codes first off and see if it throws a code or codes. The tech library shows how to pull the codes. I believe all you need is a jumper wire and your check engine light will flash you the codes others here will know the best way to retrieve the codes. It is possible the part store gave you the wrong temp sender just ground the wire to the sender to check the guage is working correct then go from there.

 

[killj0y]

My lima never goes past the quarter mark. The only time it did it was when my heater valve exploded and dumped all my coolant and even then it only went as high as half to three quarters before I realized and shut it down. I've had it as low as needing a full gallon of coolant before it actually warmed up past the quarter mark.

Usually it sits at the bottom line, goes up to just under quarter or so then the thermostat opens and back to the bottom immediately. Runs cold as Hell. Thought about putting up some cardboard but it would affect ac function.

 

[RonD]

Thanks for the input Ron,

I didn't see a two wire sensor near the gauge sending unit, but I will look for one tomorrow.
Is there a way to test the two wire unit for function while it is in place?
(voltage, resistance?)
CZ

Good info at this site on Ford EFI systems:
http://oldfuelinjection.com/?p=28

This is the ECT page ^^

As said ECT doesn't effect temperature, it just "reports it"

I would do as kimcrwbr1 suggests to test the gauge first, just to make sure the visual cue is accurate.
Sender is a 1 wire unit so uses the engine as the ground connection, this means the threads on the sender need to have good metal to metal contact, so no tape on the lower threads of a 1 wire sender, it will through off the readings.

Key on....disconnect that 1 wire from the sender.
Temp Gauge needle should go all the way down or all the way up
Ground that 1 wire, gauge should do the opposite, go all the way down or all the way up
That means wire and gauge are OK, if this doesn't happen or gauge needle doesn't go all the way in one direction then that circuit has a problem.

 

[Mac]

I just know where mine normally sits 99% of the time, if it differs much I check it.
Dave

 

[CaptonZap]

Good info at this site on Ford EFI systems:
http://oldfuelinjection.com/?p=28

This is the ECT page ^^

As said ECT doesn't effect temperature, it just "reports it"

.

Thanks Ron, that site is a great help!
I found the ECT, and will test it next trip. The chart with temp/ohm readings is just what I was looking for.

The dash gauge works, it just reads low when the block temp is 195deg, and I was wondering if that was normal.

Thanks again, CZ

 

[CaptonZap]

I just know where mine normally sits 99% of the time, if it differs much I check it.
Dave

Can you describe it's position relative to the left leg of the arc between the L and H on the gauge?
That would give me an idea of this one's accuracy.
Thanks, CZ

 

[kimcrwbr1]

It could be just a weak connection for the sending unit or the sending unit does not have good contact with the engine ground. I kept having problems with mine so I found two brass nuts to fit the threads for the sending unit then soldered a lug connector on the sending wire and bolted it tight.

 

[Fords4Us]

Good morning all. I have a related question, but it's the opposite problem. My '83 Ranger is running hot, way hot. For most of my ownership, that needle has been dead center of the temp range. But about six weeks ago, one day it soared close to the top of the gauge and stayed there. I was concerned I wouldn't make it home, but didn't want to park it on some rural road and walk, so I chanced it. Got home without it actually hitting the high mark, but dang I was close. My oil pressure gauge was also running slightly high. Got home and let everything cool down, then checked all the fluid levels. Radiator/coolant was normal with no apparent leaks. Oil was normal and no milky look to the oil. Took it for a short test drive a day later, and everything is fine. A few days after that, both those gauges ran high again, but not as badly.

Since then it's been off and on. Started to wonder if the instrument cluster was the culprit, particularly given the intermittent nature. Also had issues with the fuel gauge once or twice. I was already taking it into the shop for unrelated issues about three weeks ago, and asked them to check it. They couldn't duplicate any of the gauge problems, and suggested replacing the instrument cluster as a way to eliminate that as a possibility.

So I've been living with that for awhile now, trying to tell myself it's just the gauges. But it's gone from intermittent to just about every drive now. And yesterday we ran really hot again, with the oil pressure gauge higher than it's been before, and once again I wasn't sure I would make it home. So is there anything else I can check or do besides replacing the instrument cluster? I liked the idea of testing the wires leading to the cluster, but couldn't find info in Chiltons about what to look for. I'll go read through that TRS link already provided and see if that helps shed some light on this. Any other suggestions? Thanks all - you're keeping one more Ranger in service with all your help. The old girl and I both appreciate it.

 

[RonD]

First, is the engine actually running hot?
Normal operating temp of the engine is 200-220degF
When gauge is at half way, warmed up, feel the upper rad hose to get an idea of "normal" temp, then after gauge goes up pull over and feel it again and see if it is alot hotter.
A thermometer would be better but you use what you got
If it doesn't feel alot hotter then I would guess it is a gauge issue.

I think the '83 still had oil pressure sender not a switch, which means the temp, oil and fuel gauges are all resistance based gauges.
Fuel gauge is a little different but could be effected.
When oil is heated up above 230degF oil pressure should go down not up, that's a clue that electrical could be the problem.

What the oil, temp and fuel gauges have in common are the grounds.
Another is the overall voltage in the system.
I would first test the voltage at the battery with engine off, should be 12.3-12.8v, below 12.2v would mean to start looking for a sale on batteries , that's not the problem but next cold morning may require a jump.

Now start engine, test battery voltage, should be above 14volts, wait a few minutes then test voltage again, after recharging from the startup the alternator(voltage regulator) should lower the voltage to 1 volt above battery voltage, so 13.3 to 13.8, that's the voltage that will keep battery charged but not "boil away fluid".
If voltage is above 14.7v then regulator is bad, if external, check connections but probably need to replace it.
High voltage makes gauges run higher.

Now the grounds.
Make sure battery ground leads are clean and tight, big wire should go to the engine block, smaller wire to radiator support(head light ground).
There should be a ground strap from the engine to the firewall, usually from one of the heads, make sure this is clean and tight at both ends(this wire was loose on my '94 and caused up and down gauge issues).

Under the drivers side dash will be grounds hooked to the firewall, make sure these are clean and tight, these are the dash board gauge grounds.

 

[Fords4Us]

Thanks Ron. I didn't have any driving to do today, but I did get the battery testing done that you suggested. It's a relatively new battery and it passed those tests with flying colors. I started to trace out the wiring like you suggested, and ran out of daylight. I'll finish that up tomorrow and check the grounds as well. Now at least I have something to go check and either eliminate as an issue, like the battery, or hopefully confirm is the culprit. I'm also going to get one of those infrared temperature meters so I can get the actual temps while at normal and then again when the gauge says it's running hot. I did the radiator test and was able to establish a baseline that when the gauge is dead center, I can hang onto the upper radiator hose for about 30sec before it gets uncomfortable. It occurred to me that even if we determine that the engine temp is truly going up as the gauge goes up, ie I can't hold onto the radiator hose as long, we'll have no way to determine by how much, except with an actual meter. So that's on the buy list for tomorrow.

Question though - you said that the oil pressure would go down, as the temp went beyond 230F. Can you explain why that is? I would have expected that pressure would go up as temp went up, so that part caught me by surprise.

Thanks again for your help. Comforting to start to get info on how to nail this gremlin down, other than just start replacing stuff with fingers crossed. That approach always bugged me (expensive too).