Question about Dometic Rooftop RV Air Conditioner

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I have an old type roof top a/c unsure of the model or make no tags. It starts and runs for about 60 seconds then stops but the compressor still runs. I replaced the run capacitor with no luck.

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You might try removing the cover on the compressor where the wires hook up and see if there is a little black overload, usually the common wire is connected to it and then there is a wire from it to the common terminal on the compressor. If you have one of these overload protectors they can get weak or the wire can be loose causing a high amp draw.

Posted on Jul 24, 2009

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I need a wire diagram for about a 74 intertherm sch-10. Fan comes on but will not come on when I turn on the compressor.

Posted on Aug 17, 2010

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Posted on Jan 02, 2017

  • 49 Answers

SOURCE: duo therm roof top a/c

Sounds like 1 of 3. Blower motor capacitor, relay or thermostat. Try to run fan only if that is an option and see.

Posted on Jun 01, 2008

motor1258
  • 6674 Answers

SOURCE: Coleman rooftop a/c unit, fan runs, compressor come on/off

First of all, Shut off power to A/C unit. !! Next,You need to remove the filter /cover ceiling assy, and with a flashlight, look way up inside and you'll see the cooling fins etc, that look similar to the back of the AC on the roof. If they appear dusty/dirty, then they need to be cleaned. I use a shop vac with a couple of extra extensions to reach, and duct tape a pot scrubber brush (half round or round with nylon bristles) to the extension. Then start as high as you can get on the fins, and come straight down, kind of like combing the fins, but not pressing super ******* them. Move over, and down again, until you get them all, or at least as much as you can. (Thats basically the same as your return air at home) I use the nylon scrubber because the brush attachment with vacuum is usually softer bristles, and doesn't get in there as well. If yours does, great.Make sure you wash out your foam filter in a little dish soap & water before you put inside cover/filter back up. Now to the best part, The upper unit on the roof. You need to remove the plastic cover, by removing the 4 screws holding it on, or if it's dometic type, screws all around near the bottom of the cover, and lift it off. The front of the colemans have a lip that the cover is down over, so you may have to pull cover forward & up, then it should all lift up & off. Here's a spot to be real careful, and ready for wasps & bees. Very few, if any that I've done over the years, haven't had a bees or wasps nest under them, so if you can do it on a cloudy day, or at least be ready to move quick, and have a wasp blaster spray with you, it may be smart. Just don't forget your on a roof when you start moving !! Another thing to remember too, is that the roof can be very slippery when wet, or dew is on it, so watch out!! Be careful !! Now with cover off, look at the fins on back of the unit, and clean those the same way, or spray with a garden hose, and soft brush, and clean them up. Next, look at the opposite side of those coils/fins, where the fan blade is in front of it, and lightly wash it down as best as you can with the hose, spray nozzle, and a brush if possible. Remember when using brush, up & down as much as possible, to avoid bending the fins over. If you can't brush it , just spray it as good as you can, to clean it. Water should not enter trailer, unless maybe if you go overboard with spray, and pressure. If you have access to an air-line to use up on the roof, that's good to, but a lot of times, the water will wash it down better. This will more than likely cure your problem, if you get it cleaned out. At the RV resort where I work as a Technician, we usually have a flat rate of approx. $50 CDN. for me to do it for you. 95% of the time it cures the early cut-out of compressor, and people actually report it cools better than it has for a couple of seasons. It has to be clean to do it's job properly. When those areas are dirty, the upper unit (compressor etc) has to work so hard to cool, it overheats & cuts out, until compressor cools down a bit, then comes back on, until it heats up too much again, and kicks out again. That's why it doesn't do it as much in cooler times, because compressor doesn't get as hot. Your also shortening the life of your unit too.

Posted on Aug 14, 2008

  • 415 Answers

SOURCE: AC compressor hums for a few secs then cycles off for few secs

Inspect all electrical wires and connections and correct any areas that appear damaged or overheated or loose (connections). There is a capacitor which is a round or oval component in series with the contactor and the compressor. Thoroughly mark all connections and remove the component. Take it to you local RV air conditioning repair shop and have them test it. If it is faulty, they will provide you with a replacement part. If it is not faulty and all wiring is okay, your compressor is locked up and will need to be serviced by a professional air conditioning technician.
Try the wires and the capacitor first.
I hope you find this information to be very helpful to you as a good, solid jumping off point moving forward.
:-)

Posted on May 19, 2010

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1 Answer

Looking for model number on older Fedders air conditioner


There will be a tag on it externally and it is probably hard to read due to weather and grass clippings. If its a really old one, the tags were aluminum with the info stamped in them. If it was made in the mid 80's or later, it was probably a clear plastic tag that has faded and lost its ink over the years or is completely gone due to UV light deterioration.

Open the electrical cover, sometimes the manufactures printed model and serial numbers on the actual wiring diagrams. As a last resort, write the numbers down that are located on top of the compressor dome. Also note the brand of the compressor. Call a local HVAC shop and ask them the capacity of the compressor which is coded within the numbers on the dome. For instance a Tecumseh AH5540E is a 40,000 btu compressor that can be used in a 3 or 3 1/2 ton a/c. It'll get you in the ball park.

If you are looking for the Feddars model number so you can order parts, don't bother because those old units all had reasonably generic parts that ANY supply house has on hand. Double pole contactor, 30, 35 or 40 mfd run capacitor. 250 mfd start capacitor. 1075 rpm condesor fan motor.....ALL normal in stock items. Even the replacement compressors were generic on most of the old units and compressor brands could be interchanged with a few piping modifications.

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1 Answer

Compressor starts and runs for 15 seconds and stops. tested capacitor 15 mfd .i can hear the start relay open on start up and compressor stops . can it be the relay.


Its possible to be the relay, but if you have access to an amp meter I would see what the rating for your compressor is, it will be on a tag on the compressor, and see if its drawing too much or too little. That way you know if the compressor is bad. I've seen too many times on that particular brand techs change the relay just have the compressor fail two weeks later.

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I need to set up a intellisys controller


David ,I will need more info like type of intellisys controller. IR actually has at least 4 intellisys controller. Need to know what controller you have. Model and serial #, HP, voltage, Ep,XF,HP, Y-delta start or DOL start. pressure rating from ID tag. Some info can be obtained from the metal tag affixed to one end or in the electrical compartment (ID tag)

Nov 02, 2011 | Ingersoll Air Tools & Compressors

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I need to know what type freon goes in a Coleman Model 7333-881 roof unit on my RV


should be on the nameplate along with how much freon is in system, also if you pop the lid and look at the tag on the compressor should tell you as well.

Jun 26, 2011 | Heating & Cooling

1 Answer

Coleman roof top rv air no cool,warm compressor


No Cooling.
Turn the selector switch to “Cool” and the
thermostat to a low temperature (below room temperature).
The fan runs OK, but the unit does not cool. When the unit
housing is removed, we observe that the compressor does not
run; however, it periodically hums for 15 to 30 seconds.

Possible Causes- Check all of this before buying a new unit, that may not be the solution.

“The voltage could be low – ”
a) Check the voltage between #1 on the
overload switch and the “R” terminal of the
compressor while it is not humming. This
voltage must be 115 volts domestic USA
models or 240 volts export/overseas models.
No less than minus 10% is allowable.
b) Check the voltage from “C” or “R” of the
compressor while it is humming (trying to
start). The latter reading will probably be
lower, but it still must be 103.5 volts
minimum domestic USA or 216 volts
minimum export/overseas models.
If the first reading is above 103.5V domestic USA and
the second is under 103.5V domestic USA, there is
too much voltage drop in the lines - a situation which
must be corrected for the air conditioner to perform
safely and satisfactorily.
2. “A capacitor could be shorted, weak or open.”
Turn the power off.
Caution – There is always a chance that a capacitor is
holding a residual charge, so before touching a
terminal, discharge the capacitor as explained earlier
in this booklet.
Remove capacitors, visually examine them and test
them per instructions given in earlier section on
capacitor testing (See page 9).
If the capacitors test OK, replace them and carefully
reconnect the wires. Be sure the wires are connected
to the right terminals.
3. “Start relay contacts could be open – ” if so equipped.
Turn off all power, then check for continuity with
ohm meter between terminals 1 & 2.
4. “Compressor start winding could be open or
grounded.”
Check compressor windings per instructions. See the
section on the compressors (See page 8).
5. “Compressor could be mechanically stuck.”
This very rarely occurs and when it does, it is usually
after a lengthy shutdown. This should be considered
only after all the above possible causes have been
positively eliminated. To free a stuck compressor, use
your hermetic analyzer according to the
manufacturers instructions.

Jun 27, 2009 | Coleman Mach III Air Conditioner

1 Answer

Fan stops turning after about 30 seconds


this sounds like one of your capacitors has failed
using an insulated screwdriver and, power not applied remove the spade connectors from one of the capacitors then short the capacitor to ground to discharge it replace the spade connectors apply power and, turn it on if the problem changes replace the capacitor (a bad capacitor usually is "bulged")
there are usually two capacitors a run and, a start

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2 Answers

Compressor starts then stops after 5 seconds


Installed hard start Kit for this little freezer. No help. Needs new compressor.

May 28, 2009 | Freezers

1 Answer

Compresor will not kick on. all fans running, thermostat control works, and relays seem fine. The fridge is only 5 years old. Whirlpool 21.0 cu. ft. Top Freezer Refrigerator Plus Ice Maker.


Compressor won't run or it is "clicking' on and off: This normally could be a bad start relay and over load for the compressor, dirty condenser coils need cleaning, condenser fan motor is not running or the compressor itself. To check the compressor properly you should test it with an amp meter, each compressor is rated in running amps  ( see model/serial tag or the sticker on the compressor )...if the compressor is drawing too much current, this may be why it is shutting off. Check the model tag for proper amp rating. Some relays will be easy to notice the broken with them, they may be burnt. Example oneexample twoexample three. Some of these relays can be removed and give them a little shake, and if they rattle around inside the relay is likely bad. Compressors can also seize and click on and off or one of the electrical windings inside the compressor could have opened up. You can use a test cord to help check the compressor and this also will help with the amp test. If the compressor checks ok and you want to install areplacement start relay. You will need to find out which winding is which. You will need an ohm meter to determine the windings. First check to see if you have windings in the compressor. Then check to see if they are grounded. If the compressor has windings and they are not grounded, you can find which winding is which. Check for grounded windings by reading from each terminal to a good ground on the cabinet. Read from the top terminal to the lower left terminal. Read from the top terminal to the lower right terminal. Read from the lower left terminal to the lower right terminal. Write down the resistance of each reading as you go. The highest reading you get will be the run and start winding of the compressor in series with each other. The other terminal left will be the common terminal. Read from the common terminal to each of the other terminals. The terminal with the lower resistance will be the run winding. The higher resistance the start winding. Using the original style relay is always preferred, but using a general replacement can "get you by" if needed.

Apr 03, 2009 | Whirlpool 21.0 cu. ft. Top Freezer...

1 Answer

I am a ac tech, and i was working on a old carrier unit, wich had no schematic diagram. I need it in order to get the compressors going. if i give you a model # can you please provide one. roof top ac...


you aren't an ac tech number one but i shall overlook that . your question is llike will the sun come up in the north or the south tomorrow. obviously in the east as it has since the earth was created. anyway. all compressors since the beginning of time wire up the same .a wire commonly referred to as the common goes from the contactor to the compressor. usually black in color, hence the old coloqualism Blacks are common. the run wire is from the contactor to the run side of the run capacitor or from the contactor to the run connection on the compressor. hence the old slogan reds run when you point a gun at them. the only wire left is the start wire that come from the start capacitor and is usually yellow . hence the old saying blacks are common, reds run, and yellows are always starting something. very ethnic i know but thats how i was taught.now that the wirings correct check to see volts through contactor are correct and if one side of contactor is not feeding. if volts good then check capacitors with a cap checker. if all else looks good kill power and inspect compressor terminals at compressor. if burned off consider a termilock kit good luck..

Jul 19, 2008 | Goodman CLQ36AR49 Air Conditioner

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