Air conditioner showing wrong air temperature - problem with temperature sensor?

LaRea

My Marine Air Passport air conditioner has developed a fault with the temperature sensor.  The temperature displayed on the keypad hovers around 64-67 degrees no matter what the temperature is.  Anybody seen this before?

If keypad says 67 and I set the desired temp to 65, the AC comes on and works fine, so it's not a problem with the compressor/fan unit.  I tried unplugging/replugging the cable on the back of the keypad.  Any suggestions what to try next?

rasbury

Like it's not calibrated? If so Google that and I think you will find how to recalibrate which I had to do...if you can't find it let me know...I think it was covered in the user manual but it was a while ago....

Handymans342

Try powering down the whole unit and wait 10 min. If that dont work do what Ras said. If that dont work slap a Ford sticker on it

reneechris14

Mine acted funny last week held the power botton to go in to the p codes and it reset it self now seems to be ok. 

LaRea

Power-down didn't work ... we were anchored all day yesterday without running the genny.  I also tried a factory reset - no luck.  Ras, I'll try the sensor calibration next.

Apparently the sensor is built into the keypad.  There's also an option for an external ("alternate") sensor.  Maybe I'll get one if I don't figure this out.  The manual says:  "the installation of an optional alternate air temperature sensor (located in the return air path) will greatly increase the effectiveness of the de-icing feature, and this option should be considered whenever the display sensor cannot read the room temperature accurately."

rasbury

I would try the recalibrate first- if it worked before ok then it should work now!

Handymans342

Bad stat or control board that's all

Ian

I was able to adjust mine via program parameter U5 per the manual. Have it?

LaRea

Yes, that's the sensor calibration.  I'll try it this week.

Stodge

I had something like this happen and I ended up having to replace the A/C display and the control board on the A/C unit.  The display was no longer available and the newer one was not compatible with the control board on the A/C.  

Dream_Inn

I agree that it more than likely needs adjusted.  It's a pretty straight forward procedure.

rasbury

We always jump to the worst possible scenario don't we??

Ian

I adjusted mine by checking the temp at the controller and then tuned the parameter. Recently I looked closer at the unit itself and looks like I have a remote sensor at the unit picking up return air temp so I will need to adjust again a little.

GMSLITHO

I have a 2002 270 never had air before on a boat it works great but will only run full cold where is the sensor located for it 

Ian

On mine in front of the coils where the return air gets sucked through.

GMSLITHO

Thanks Ill take a look 

Dude_Himself

You can probably solder a new temperature sensor on the board - sounds like that's what failed.

rasbury

@GMSLITHO Get the manual and make sure it is calibrated correctly- had the same problem with mine when we first go the boat....

GMSLITHO

Thanks you wouldn't have a link for it ,would you ? 

rasbury

I think I have it on my computer at home...sense a pm and maybe I can send a link...

Ian

Here you go, note TOC links don't seem t go anywhere now.

MarkB

So two things, check firstly where your temp sensor probe is. Mine was just behind the air intake grill in the mid berth.  It was making contact with metallic COLD components. I moved it away and secured it so it wasn't contacting anything and could get a good read of the intake air temperature, and that fixed most of the problem. To get it totally fixed, I calibrated on the thermostat ... to fix the last 2F it was off.

rasbury

https://www.pocketyachtco.com/wp/wp-content/uploads/pocketyachtco.com/2017/10/MarineAirPassportIOmanual.pdf shows how to re set the ambient temp...that was my problem and worked like a charm ever since....

LaRea

Well, if it's using the sensor built into the keypad, the sensor definitely is not working.  The sensor is a tiny little nub at the bottom of the keypad.  I held a bag of hot water against it for a couple minutes, and the temperature reading didn't change at all.  

I can force the AC to come on by changing the calibration, but it would just run continuously.  I doubt we could sleep with it like that.  It would be colder than a meat locker.  

Next time I go over, I'll see if the system has the external "alternate" sensor.  Didn't have time today.

LaRea

Fixed.  My system does have the external temp sensor, and it was reading about 15*F too high.  Replaced it and all's well.  The part was $45 from my local marine AC guy.  I searched high and low to find the part online, and never did find it.