Ic Aguilar

Hello all, first time here. I just bought a 08 F150, 4.2 that has the temp gauge that does not work. It is buried below the C and just click moves when turning the vehicle on and also off.

Jimboy

You need to get the Diagnostic Trouble Codes (DTCs) and report back. Autozone and others do this for free but they can only read "P" (Powertrain codes) as far as I know and unless you have access to a more sophisticated code reader we can start with the "P" codes. Do you have a check engine light illuminated?

This could be a circuitry issue.

FWIW - The Cylinder Head Temperature (CHT) sensor on your 4.2 L is on the back of the driver's side cylinder head and its wiring could potentially come in contact with the exhaust system. If you can, visually inspect this wiring for possible damage.

PS: I looked up the cost of a new Motorcraft CHT on RockAuto and was surprised at how expensive a new CHT is, $111 plus shipping. I would have expected more like $25. Also note that the CHT comes in direct contact with the engine coolant, meaning the cooling system will need to be partially drained to replace the CHT.

laterongc

I don’t recall how to initiate it (without searching), but there is a way to do a gauge test mode. Basically it will cycle all your gauges so you can visually see if they all work. Id start by doing this so you know if it is a physical problem with the gauge.

you can also get a scanner or some obd device that lets you see/read temps, and you can watch the temp readings and see if they seem possible/reasonable,

if you do these things, you should be able to identify source(s) of your issues.

dsg2003mach1

this.

I believe you search for "engineering mode" to get the digital cluster to change over, it will display coolant temps in C or use another scanner to see coolant temps and figure out if there is even a valid signal or not (sensor, wiring etc...) or it's the cluster itself

laterongc

BareBonesXL

Does the engine run? Is there a Check Engine Light (aka Service Engine Soon). If there's no CEL then the CHT sensor is probably fine since the PCM uses it to run the engine.

45K40

IC Aguilar,

Try this:
https://www.f150forum.com/f38/instru...st-mode-38916/

45K40

Ic Aguilar

The service engine light is on and the engine runs a little rough. I did the "hold the trip reset (xl model) down then then turn key" all the gauges tested. The temp needle went further down, almost a half spin then back to where it was at and still does not work.

BareBonesXL

If it was mine and I suspected the CHT sensor I would unplug it and measure resistance across the two pins. It's fairly easy to get to. I don't know what resistance should be but if it measures in spec. then you can look at the wiring.

It is a simple electrical component, easy to test.

I'm not sure how Ford's system works but a common test on others is to short the pins on the sensor connector Typically that will cause the gauge to go full hot.

These are just ideas. Do the leg work to find out the details.

laterongc

I’m guessing that either this gauge broke OR it was previously taken apart, but needle was misaligned when put back together. Regardless thought at this point you know there is an issue (physically with gauge on dash)

if I were you I would next get a scanner that can tell you if pcm appears to be getting proper temp readings (I bet it is).

if it is then you can decide what makes most sense moving forward (ie ignore all together, fix dash gauge, or get a cheap device to read/display temps via obd Port and ignore dash)