AC working right?

I tried pulling more if the tube out above the filter this morning. Will see if the camper is warm later.

Unlike some capillary tubes, there is no bulb on the end. Therefore the whole length of the tube is involved. The "bow" of the connection box has a small gap that would allow chilled air inside. I thing a bit of tape might be in order.

If that doesn't work...

Thanks to all, especially wa8yxm who encouraged me to keep looking for that tube.

SoundGuy wrote:

wildtoad wrote:
One other thing to look at is if an air outlet is blowing directly on the thermostat.

It's hard to imagine a truck camper would have anything but a direct blow A/C with the thermo mounted on the unit itself as part of the ceiling unit. :R

Yet somehow our truck camper came stock with a wall-mounted digital thermostat that controls both the furnace and ceiling Polar Cub 9200 A/C unit. ;)

Went out and looked at ours. It's a Mach15 and the controls are on the forward end of the ceiling unit. But it's a Coleman with a "Free Delivery" ceiling unit. I can see on ours, when I drop the filters out, that the Sensing Bulb, from Thermostat (Key 4 on Diagram) is entirely in the INTAKE (air Return from Coach Interior through Filters) part of the Ceiling Unit. Right under a Filter. Ours happens to be on Driver Side.

This tells me the Bulb from your Key 4 thermostat should be exposed ONLY to air being returned From the Coach Interior FOR Chilling. ***NOT*** in any Cold Air being Discharged out the ENDS of your ceiling unit.

Is the FABRIC DUCT COLLAR (Key 1) in place? Its job is to make sure that ALL air being drawn in through the Filters in the Ceiling Unit (your linked parts list) goes UP into the Rooftop Unit ***AND*** make sure no Chilled Air gets into the Return (from Coach Interior) area.

I think something is installed improperly or incompletely. Chilled air is getting onto that Bulb, and the Bulb should be looking only at RETURN air.

Looked again and found the sensor. It was located where it couldn't be seen, coiled up above the boat.The end was in contact with the cold air duct below it. Raised it up and pulled the end out over the passenger side intake filter. It's working much better now, and seems to be dropping the temperature in the camper a bit. It still won't run continuously, though. Seems to work at about 50% duty. Maybe some more tweaking of the sensor position is needed.

The unit is brand new, no time for the filters to load up. Plus, when I lifted the shroud back into position and the compressor kicked off, there were no filters in place.

This looks like the setup.

Note that with the shroud in place, cold air from aft (left in the diagram) traveling forward to the front louver and bed area (right in the diagram) is forced around the sides of the boat shaped connection box that houses the thermostat near the bow. I'm wondering if I'm experiencing a design flaw.

To those with working Colemans: Does yours looks like this?

Sounds like you need to clean the intake filter.. Find the T-Stat sensor (look around) on my Coleman the thing was just hanging there in free space but it is an after market install. On my Carrier controlled Advent Air it's stuck in the evap coil.. THat one will cycle if it gets too cold.

I have the same unit in a 14ft cargo trailer. Generally it will run for maybe an hour or more to cool down the trailer then cycle, but cyle is more like 10 minutes on or more then off. I highly suspect from your description and statement that something is amiss in the unit rotary thermostat causing the compressor to cycle. maybe it is getting airflow it shouldn't.

Another thing that can cause vehicle A/C systems to cycle ON/OFF rapidly and not cool well is a low refrigerant level.

A tiny leak in the system can of course cause this. Rare ... but it can cause what the OP is experiencing.

No wall stat, all control is at the ceiling. I removed the knobs, grilles, filters, and shroud this evening. As soon as I dropped the shroud, the compressor came on and stayed on. Put the shroud back up, and the compressor shut off again. No bulb sensors evident.

Three things can cycle it off. In the case of a COLEMAN with "Local" (not a wall mount thermostat) there is one more.. And I'm suspecting that last one.

If your controls are knobs on the ceiling in roughly the middle of the grill....

Remove the knobs. tehn teh grill and filter

There si a small "Tube" with a bulb on the end

ON my Carrier's this was the frost sensor and it was stuck in the evaporator coils but on a COLEMAN with ceiling controls THIS SENSOR DOES NOT EXIST

The sensor that LOOKS LIKE IT. it the room air temp sensor and is NOT supposed to be poked into the condenser.. It's just supposed to hang there in free space. Why they did it that way I do not know and I can see several "issues" with doing it that way Find a place you can zip tie it down and be happy.

THIS ONLY APPLIES TO CEILING CONTROLLED UNITS. If you have a wall-T-Stat this does not, far as I know, apply.