Cooling Fan not going high speed when idling - truck starts to overheat

[mike199]

Thank you guys for all the answers, I will get someone more mechanically inclined to check all the suggestions and clean up the radiator area(although like I mentioned, it worked one day and stopped working next morning, so I am thinking it didn't get full of debris just overnight to cause the issue but I will check that as well)

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[RangerBill]

If I am reading correctly then it should read between 0.75V to 0.04V is that not correct? The one above it is running and not reading correct.

I don't know where your range of voltages for the ECT came from, but the calculated temperature for coolant and CHT match in his diagnostic readout and are in a normal range for a fairly cool engine, so I am not seeing a temperature sensor problem.

 

[airline tech]

Yes temp sensors are normal- however just need to confirm the Ambient (Raw & Filter) mismatch normal, I think it is but would like a another truck compare to verify.
I truly think its a flow issue, be it bad reservoir cap and not maintaining 21 PSI or internally restricted radiator or worn impeller on water pump or a blocked radiator (airflow) and then a slight possible on the voltage drop on the circuit.

Any of the above can cause both issues @ idle and the CHT & ECT temp sensors are not picking up actual correct temperature - from the flow issue.
It just needs pinpointed down to which one of the above or a combination of the above is the root cause. as
The issue only happening @ idle is the most important factor for this as above idle, you are able to overcome the flow issue either (airflow or coolant flow - circulation)
The AC issue is secondary, I believe the hot radiator is preventing the condenser from removing the heat from the Freon and also possibly internal pressure is increasing and the AC Clutch may be disengaging, I think its more just the the condenser cannot remove the heat

 

[airline tech]

In a Ford Ranger, the engine coolant temperature (ECT) sensor typically outputs a voltage that varies with temperature, providing a signal to the Powertrain Control Module (PCM) to regulate various engine functions. Normal operating temperatures usually fall between 195°F and 220°F (90°C to 105°C), with corresponding voltage readings around 0.75V to 0.04V. If the voltage reading is outside this range or if the temperature gauge reads incorrectly, it could indicate a problem with the sensor, wiring, or the PCM itself.

If I am understanding what I am seeing your ETC is out of range.

For ref: 38 Deg (C) = 100.4 Deg F

Here is a voltage / temp ref chart - so the voltage of 2.273 is normal.

 

[mike199]

Yes temp sensors are normal- however just need to confirm the Ambient (Raw & Filter) mismatch normal, I think it is but would like a another truck compare to verify.

I think it was due to the heat soak, on cold and before overheating (just a few mins of idle they show the same value)

 

[airline tech]

I think it may also be a good idea to check the PID for the AC High Pressure Switch, if reading incorrectly may also be causing the issue

 

[mike199]

Just with diag tool is okay or multimeter at the swtich?

 

[mike199]

Knock on wood, but after cleaning the debris from the lower part of the radiator between the condenser, after 1h and 15h of idle, ac was still blowing fairly cold, coolant temp was at 97c. Didn't hear the fan kick in though but it was around 15c outside today so I will be testing in the next few days as well. If that was the actual solution, I will be amazed.

 

[airline tech]

Cool, hopefully it cures the issue.

I hooked up my scan tool and verified that yes, the Raw & Filtered can be displayed showing a mismatch.
Note: I had been idling for a long period to simulate what you would see.
Also noted that my Fan Speed never increased as the PCM did not command the Desired Speed above the engine RPM while at idle and engine at operating temp
Note: 0% Desired = Engine RPM, if the PCM determines that a greater fan speed is needed for (Engine Parameters / Load Etc) it sends a PWM signal to the fan to increase its speed viewed as a percentage (Desired) and RPM for the fan speed.

 

[mike199]

Cool, hopefully it cures the issue.

I hooked up my scan tool and verified that yes, the Raw & Filtered can be displayed showing a mismatch.
Note: I had been idling for a long period to simulate what you would see.
Also noted that my Fan Speed never increased as the PCM did not command the Desired Speed above the engine RPM while at idle and engine at operating temp
Note: 0% Desired = Engine RPM, if the PCM determines that a greater fan speed is needed for (Engine Parameters / Load Etc) it sends a PWM signal to the fan to increase its speed viewed as a percentage (Desired) and RPM for the fan speed.

Today with a bit warmer weather it did not overheat, coolant was about 92-94c but even on the lowest ac setting, it wasn't blowing as cold as it does when driving, so I am guessing my issue is mostly resolved but not completely, I do remember the fan kicking in very often before and ac being as cold while idling for a few h as it would be while driving. Even my wife's mazda cx-5, whenever it's stationary with ac running in a warmer weather, the fan would go up and down several times during like a 5 minute stop, but I am guessing I will sell the truck sooner than find the actual issue lol.

Thanks for all the help!!!

 

[airline tech]

I have a hunch here but I cannot locate any specific information on true operation of the Fan Clutch and what specific temp / pressure etc - where it will increase speed @ idle.
There are many inputs that the PCM uses for control.
Keep in mind that this is a different fan than a true electric fan - like the Mazda, where it has a Fan High Speed or even a separate fan (dual fan) that is dedicated for AC operation.

At the time of the AC Recharge - the condenser had a blockage of airflow, that blockage of airflow would cause a increased pressure on the (High Pressure) switch which MAY have given the tech a invalid reference pressure as far as Freon charge is concerned.
So it may be possible that you are slightly under charged (Freon)

As far as the Fan Engaging at Idle (previously) I think the AC Pressure Switch was picking up a very high pressure and triggering the PCM to increase the fan speed.
You had the system serviced and that changed the pressure in the system and if I am correct now it falls below that trigger pressure. I think it is somewhere around 240 PSI for this type of fan.

Basically, the point is - Normal Ops for the Ranger, the fan should only be engaged at cold engine start and then back off and when in Idle (ops) it will only engage if the PCM sees a input issue.

So it appears you have cured the overheat issue and now the under performing AC issue MAY be from the original airflow issue.
Here is a screenshot of my idling for a long period and what I can get (Temperature Output) from the temperature sensors.

General Output - is approximately 35-40 Degrees below ambient for a properly operating system.

 

[mike199]

That sounds like a good explanation, I am also seeing the condenser fins being flat wherever the openings are in the bumper but don't think that has anything to do with this behaviour. Anyway, if it's as good as it gets without throwing more money at it with this mileage, I am okay with that

 

[RangerBill]

That sounds like a good explanation, I am also seeing the condenser fins being flat wherever the openings are in the bumper but don't think that has anything to do with this behaviour. Anyway, if it's as good as it gets without throwing more money at it with this mileage, I am okay with that

If the fins are bent, that will limit airflow through the condenser and will affect cooling for the air conditioner and engine cooling. I would straighten them for maximum cooling.

 

[mike199]

That makes sense, I will try that over the weekend. Thanks

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