Where should the thermistor inside Coleman A/C be located?

[boyscout]

On another forum I saw a post about installing baffles in the A/C units to improve air flow into the raceways in our trailers. Here's the YouTube video about doing that:

https://www.youtube.com/watch?v=3Vhv_b-1zAk

Great project, and I can feel the difference in airflow from bedroom ceiling vents after first modding the bedroom A/C.

In the course of doing this mod I found that there is a thermistor (a small metal nipple on the end of a wire) inside these Coleman units.

In the bedroom A/C the thermistor was hanging in the airflow on the return side of the unit, its wire wrapped around others such that the nipple of the thermistor was suspended in the airflow. The bedroom A/C has worked fine, not cycling too much (after we closed the wall-side vent on it so it didn't blow cold air on the thermostat) and doing a very good job of cooling.

In the living area A/C the thermistor is shoved into what feels like a slot in a wooden board up inside the return chute. We've always thought that this unit worked far too much, roaring for ages before (I guess) achieving set temperature and shutting off, even in moderate outside temps in the low 80s trying to achieve mid-70s inside. There'd be a seemingly-brief quiet time and then it would be roaring again for a long time to bring the temp back down. I am hopeful about this baffle mod improving the situation, but wonder if thermistor placement is in any way related.

So which placement of the thermistor is correct? Should it be jammed into that slot or should it be hanging free?

TIA

[howson]

So which placement of the thermistor is correct? Should it be jammed into that slot or should it be hanging free?

I can't find any reference to a thermistor in a Coleman, Mark, on any schematic nor in their EVALUATING AIR CONDITIONER PERFORMANCE document (attached).

Any chance you took a picture?

[boyscout]

I can't find any reference to a thermistor in a Coleman, Mark, on any schematic nor in their EVALUATING AIR CONDITIONER PERFORMANCE document (attached).Any chance you took a picture?

Thanks Howard. I'm pretty sure I've answered my own question, spurred by your request for a picture.

First, the thermistor:


Then, the "board" that I felt up inside the air conditioner. Seems likely that the thermistor *should* be shoved into the condenser to monitor what it's doing, as it was on our main unit, and not dangling in the intake as it was on our bedroom A/C. Thanks for the reply.

[ncitro]

Thanks Howard. I'm pretty sure I've answered my own question, spurred by your request for a picture.

First, the thermistor:


Then, the "board" that I felt up inside the air conditioner. Seems likely that the thermistor *should* be shoved into the condenser to monitor what it's doing, as it was on our main unit, and not dangling in the intake as it was on our bedroom A/C. Thanks for the reply.

That’s correct, it should be stuck into the fins. It tells the unit of its frozen up and shuts it down. As far as I know it does not have any other affect on performance or cooling.

[SolitudeAtLast]

I posted previously about our front bedroom a/c (evap coil, not condenser coil) freezing up. I called Lazy Days and the phone tech pointed out this thermistor as a possible cause, since it is supposed to sense coil freezing and put the a/c into “defrost” mode. Mine was shoved into the lower right part of the coil, phone tech said it should be on the left side as liquid line comes in on the left. My coil was freezing from the top down. I couldn’t reach the top but did move it to the left side with no improvement in coil freezing. As noted in my other post, I had to leave before trying anything else. Tech said the sensor & wire are not expensive, but local dealers did not have one in stock. I’m going back this week, and will order one to try in case sensor is bad. Other end of sensor wire plugs into a control board. Will also go on top & check for dirty coils etc. If none of this works, the probably replacement (still in warranty). Per local dealer, the sensor for my Coleman Mach is;
NTP PART # 41-0030
MFR PART # 7330A3231
COAST PART # 69842
Retail Price. $11.89

[howson]

With Doug's post and info (thanks, SolitudeAtLast!) I did a google search and found an informative entry on an irv2 forum by a member named "Hikerdogs". Here's what he had to say about the thermistor (which reinforces what Doug wrote in the post above):

The sensor you found is typically wired to the control module and is inserted between the fins of the evaporator coil. It senses the temperature of the coil and shuts off the compressor when the coil starts to freeze.

Your hot weather problem may be related to it not being in contact with the coil. In hot weather the compressor runs until the sensor detects the coil freezing up. It then cycles the compressor off the compressor until the coil warms up. If it's not in place the compressor will continue to run even though there is frost on the condenser. When that happens air can't pass through the fins and no cold air is circulated into the house.

[boyscout]

Mine was shoved into the lower right part of the coil, phone tech said it should be on the left side as liquid line comes in on the left. My coil was freezing from the top down.

Thanks, that may be useful. Mine too is pushed into the fins at the lower right (looking at it from the intake side).

Does anyone else here know if the Lazy Days tech advice that it should be at the left side is correct advice?

[Country Campers]

GDRV-Megan

This is not a model specific question so I thought I would tag you for some info.

Please read the above posts.

The question is "Where should the thermistor be placed in the Coleman A/C unit?"

I would also like to add if we could know the same location for Dometic , Furrion , and any other A/C units that are being used.

I think it would be possible for this item to vibrate loose and just be hanging around the A/C plenum and not allowing the A/C to operate properly.

Thank you

Brian

[GDRV-Megan]

GDRV-Megan

This is not a model specific question so I thought I would tag you for some info.

Please read the above posts.

The question is "Where should the thermistor be placed in the Coleman A/C unit?"

I would also like to add if we could know the same location for Dometic , Furrion , and any other A/C units that are being used.

I think it would be possible for this item to vibrate loose and just be hanging around the A/C plenum and not allowing the A/C to operate properly.

Thank you

Brian

I apologize, but I have not been able to find this information. I would recommend reaching out to Arixcel directly and the other suppliers regarding their products. It looks like Airxcel can be contacted at rvpsupport@airxcel.com.

[howson]

The question is "Where should the thermistor be placed in the Coleman A/C unit?"

colan will know. Hopefully he stops by the forum later and can fill us in.

[boyscout]

GDRV-Megan
I think it would be possible for this item to vibrate loose and just be hanging around the A/C plenum and not allowing the A/C to operate properly.

In case you missed it in my earlier posts, the thermistor in our bedroom A/C apparently did just that.