today on my 2004 5.4 F-150 the Check Gauges came on the instrument cluster and beeped. My coolant gauge had stopped working and was all the way down on "C". is this a bad ECT? It also seems that the a/c stopped cooling at the same time, but i haven't been running it a lot lately so i am not sure if it's related or not. Thoughts?

 

anyway to check for codes? your truck uses a cylinder head temp sensor. its located under the intake manifold. not the easiest to get to but its worth a shot. unlikely that both issues are related. you can get a black light and check for leak dye around a/c components. I personally would put a CHT in and re check. worst case scenario its a instrument cluster or wiring issue, but unlikely

 

Yeah, get yourself a scanguage and use the x gauges for CHT. It'll give you live updated actual temp readings. That'll tell you if its the cluster or something serious.

 

I read the codes and nothing shows. I went ahead and changed the CHT and that changed nothing. I also discovered the A/C compressor is not running. I checked the fuse for the compressor which is number 11 and it is fine.

 

Do a gauge sweep....hold down the odometer reset button, then turn the key to ACC. Once the digital display area show "check gauges", release the odometer reset button and all the gauges will do a sweep and a bunch of clicking. Hopefully that will fix it.

This does a self check of the gauge cluster. Pay close attention to the temperature/coolant gauge.

If not, it sounds like you might have a loose solder joint in your cluster. Lets hope that is not the case.

 

I did the gauge sweep. The coolant gauge went all the way over to the Hot side them back down to cold. But when i crank it back up the check gauges comes back on and the temp never moves

 

As I said before, you should plug in and see what the actual cylinder head temps are.

 

I don't see where it is a cylinder temp issue. it appears to me it's a wiring/gauge issue. The water temp itself is running normal when measured through the radiator. What would a cylinder temp do for me? Are you are trying to tell me that you believe the water temp is actually low enough to give a cold reading after running for 100 miles? Or that there is leakage into a cylinder?

 

Now it sounds like a sensor or wiring from that sensor type of issue.

As 2008_XL states, now is not a bad time to do a electronic diagnosis so you're not chasing windmills.

 

I'm saying that so you can rule it out completely and play it safe. A scanguage II is a great tool to have no matter what.

 

Your engine does not use an ECT sensor, all operating temperature data comes from the CHT sensor into the PCM. The PCM then sends a data message to the cluster which then moves the needle to a position that corresponds to its programming (assuming no faults).

Your 2004 should have the HEC Dealer Self Test function built in (Google it). That will show you on the odometer or message display what the cluster has received from the PCM as far as engine operating temperature is concerned. You already paid for it, no need to buy anything new (yet).

 

Thanks. I encountered the Self test function when ManualF150 told me about the gauge sweep. I cycled through the options and saw the temperature. So it's obviously getting a reading back from the CHT...right? does that lean back toward the cluster being bad? I ran across the YouTube video below and it sounds exactly like I am encountering and it was caused by a bad CHT harness. But if the harness was bad i wouldn't be getting a reading back from the PCM would I?

 

I finally got the time to change the wiring harness that runs from the CHT to the wiring harness. It fixed the problem. One of the two wires on the end that plugs into the wiring harness was broken. I ordered a new one from my friendly Ford dealer and that took care of it.

My Ford parts department had a hard time finding the number for the right plug, so for reference the Ford part# is XL3Z-14A411-AA.

 

@Ericht Hope you don't mind bringing up an old thread, but how did you go about replacing your CHT wiring harness? My temp gauge needle is also pegged and the self test turned out ok while the sweep gauge trick didn't do much to fix it either. Did you have to remove the intake box/manifold?

Thanks in advance!

 

Yes, you have to remove the intake. If I remember correctly the sensor is on the right side of the manifold toward the front and you can't get to it without removing the manifold. The wiring harness runs out the back towards the transmission