A/C temp sensor

[pflightnut]

Next chapter in the Monaco mystery series... I can't get the front a/c unit to shut off when it should even when the living area is plenty cool. Inside temp on 2 independent thermometers is 74/75. Kept raising the thermostat a degree at a time and waiting a few minutes. Finally, when it was set to 83, it went off in about 15 seconds. I pulled the sensor cover off the wall in hopes of cleaning or finding a bad connection. I didn't expect to find the metal shavings that I did. Could this be the problem? What other possibilities might cause the failure to shut off? The fan is on auto by the way. I'm no a/c tech, but this should prove interesting. All suggestions appreciated.

Thanks,
Steve

[Jim_HiTek]

Hmm. I have experience with that type of temp sensor and yours looks to be well protected, wires have heat shrink, no bare wires, no exposure where a metal chip could short something out on it. Assuming you are saying that the metal chips were very near the thermistor, then I suppose they could contribute to slow response time of the thermistor. But as far as throwing or skewing the thermistor's resistance that far off seems to be a stretch to me.

BUT, now that you've cleaned it out, what's happening? You can just leave it dangling too, no need to put it back in it's cage.

[jacwjames]

As they say "Location, Location, Location"


Looks like yours is mounted fairly low, passenger side wall. If the sun is hitting that side the temps will be off. Being mounted low might be OK. Does the AC air blow at it.



My front sensor is located under the upper cabinet above passenger seat. It seems to track pretty close to what I set the temp at. Close enough that I haven't thought about moving.

My rear sensor is the thermostat, mounted side of cabinet above head of bed, this one doesn't track as well but I can change the set temp to get it to cool/heat where I want it.

[RamiDav]

Most of us end up finding a comfortable setting and forget about what the numbers say. The sensor is affected greatly by the sun shining on the wall or someone turning the air off of them only to have it blow on the sensor. In other words, if I'm hot I turn it down or vice versa.
Actually, the wife and I have different opinions of how it should be set.
I turn it down she turns it up. Those are the days of our lives.

[wamcneil]

Originally Posted by jacwjames

As they say "Location, Location, Location"
Looks like yours is mounted fairly low, passenger side wall. If the sun is hitting that side the temps will be off. Being mounted low might be OK. Does the AC air blow at it.

X2... Is the sun hitting that side wall? Maybe convection is pushing hot air from the wall cavity out past the sensor?
Maybe try sealing the hole behind the sensor and maybe unwrapping the sensor so it sticks out into the room more and gets you closer to actual room temp.
Cheers,
Walter

[vito.a]

Dometic says it can take up to 5 min for the A/C unit to respond to setting changes.
My wife gets impatient and I ask her to just wait a few min and it will usually respond.

[pflightnut]

Removing the metal shavings made no appreciable difference. The room temp was 74 (about 6" from the wall), and with the thermostat set at 80, the unit just ran and ran. Upped it to 81, and it went off in less than 30 sec. Five minutes later, the thermometer had climbed from 74 to 76, and the a/c came on again. The thermistor is on the outside wall, on the sunny side where we are camping. So I guess I'll put a bit of insulation on some tape in the hole and get the thermistor off the wall, as suggested above, and see if that's the cure.

Thanks for the help and suggestions!

Steve P

[YC1]

That is mounted in just about precisely where they say to NOT mount them. Mine is near the same area and worked just as yours, depending on the sun on that side.

I don't know how many hours I have spent fiddling with the sensors in the bedroom and the living room but a lot.

Buying a new sensor and wire at least gave me something to test and measure with.

There is no way to run a new sensor short of cut and splice but here is my resolution and it has been working for several years now.

With the new sensor and wire (bundled and stuffed) into the AC intake area, the probe/sniffer end is protruding from the AC cover. This is near the actual intake air part of my Wako silencer.

I never chase the thermostat up and down any longer; it will cycle the ac on and off.

When it is extremely hot here in Central Florida the AC runs almost continuously. When it cycles off it is only for a very few minutes.

As for the metal filings, no they would not be an issue unless cutting into the sensor wiring.

And yes, I poked the sensor out of that hole, insulated it, tried to move the sensor outside the little hole to no avail.

[pflightnut]

I don't think I have the patience to run a new wire and sensor, so I Gorilla taped some insulation into the hole, extending the wire and thermistor outward a little. How much that will help is questionable. We shall see...

[YC1]

As I suggested, you can do a very simple disconnect and reconnect right inside the AC intake area. Bundle the excess wire and leave enough wire (18") approximately with the probe end free. Just tape it to the ceiling with about two inches sticking out from under the ac shroud when it is reinstalled.

Less than an hour job.

[pflightnut]

Originally Posted by YC1

As I suggested, you can do a very simple disconnect and reconnect right inside the AC intake area. Bundle the excess wire and leave enough wire (18") approximately with the probe end free. Just tape it to the ceiling with about two inches sticking out from under the ac shroud when it is reinstalled.

Less than an hour job.

Might be doable... remove inside cover, disconnect wires there, then pull from the thermistor probe end into the coach, then bundle and stuff into the ceiling. Reconnect wires. And replace cover with the probe slightly exposed. What could go wrong? I will do this after I fix my bed slide and my Summit XL topper. Pant, pant...

Owning an RV is like having a second full time job! Oh well, keeps the mind sharp, eh?

Thanks,
Steve

[RamiDav]

I think I recall reading on here that there is a temp sensor inside your wall thermostat and if your remote sensor is not plugged in the A/C unit will
use the thermostat.
I can't guarantee this is the case or that it would be any better than what you have now, but you don't have much to lose except some time.

[aggieof4]

Originally Posted by YC1

That is mounted in just about precisely where they say to NOT mount them. Mine is near the same area and worked just as yours, depending on the sun on that side.

I don't know how many hours I have spent fiddling with the sensors in the bedroom and the living room but a lot.

Buying a new sensor and wire at least gave me something to test and measure with.

There is no way to run a new sensor short of cut and splice but here is my resolution and it has been working for several years now.

With the new sensor and wire (bundled and stuffed) into the AC intake area, the probe/sniffer end is protruding from the AC cover. This is near the actual intake air part of my Wako silencer.

I never chase the thermostat up and down any longer; it will cycle the ac on and off.

When it is extremely hot here in Central Florida the AC runs almost continuously. When it cycles off it is only for a very few minutes.

As for the metal filings, no they would not be an issue unless cutting into the sensor wiring.

And yes, I poked the sensor out of that hole, insulated it, tried to move the sensor outside the little hole to no avail.

Where did you get the additional sensor? Was it just a generic or OEM?

Thanks,

[YC1]

https://www.adventurerv.net/sensor-k...sroih1ggni64l0

Glad you asked. I had to do some repair on my web page link for the sensor.

As I recall my AC would stop without the sensor plugged in. I did not do any resetting with it disconnected to see if it would revert to the hallway 5 button control sensor, if that makes sense.

The hallway one would not likely work for my living room area.

As a side note I have spent more hours working on the AC intake, output, and ceiling registers than I care to share.

Designing silencers took up many hours as well with some really good results. Short of some way to mfgr them like Wako it is impractical to build commercially.

My hat is off to Wako for making a fine product. It could use some refinements but at some point in time you have to go to market.

I find that just getting the air intake opening redirected away from the seating or living area reduces the sound by enough to not have to chase the tv volume.