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Old 07-17-2021, 07:16 PM   #1
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Ac repair

We have an 88 sunline satellite classic..the ac motor quits working when it gets hot...blower fan spins free but when I it it turned on it get tight..motor replacement or whole ac replacement
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Old 07-17-2021, 07:33 PM   #2
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You mean it just sits there and hums, and/or turns very slowly? Probably just a bad capacitor.
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Old 07-17-2021, 07:52 PM   #3
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If I help the fan it will try to run..I left it off for about an hour and it started up but stopped in about 30 seconds
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Old 07-17-2021, 07:53 PM   #4
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Like it has a tight spot when the ac switch is on
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Old 07-17-2021, 08:08 PM   #5
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Sounds like a pretty classic case of a bad capacitor.

The good news is, the part is only about $3-4. The bad news is that if you need to pay someone to correctly diagnose and replace, probably a couple of hundred.
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Old 07-17-2021, 08:09 PM   #6
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Why would it be hard to turn then
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Old 07-17-2021, 08:19 PM   #7
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It's been too long since I was into motor theory to have an elegant explanation on the tip of my tongue.

But if it turns freely with no power applied, then resists turning with AC power, that means that magnetic fields are the cause of that resistance. A proper amount of capacitance in the circuit causes a phase shift that helps the motor to turn. Less capacitance, less help--clear to the point that it will resist turning.

Those capacitors typically contain a moist electrolyte between their plates. After 33 years, good chance it's dried up.
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Old 07-17-2021, 10:21 PM   #8
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Quote:
Originally Posted by Buffetman View Post
We have an 88 sunline satellite classic..the ac motor quits working when it gets hot...blower fan spins free but when I it it turned on it get tight..motor replacement or whole ac replacement
I have not been into an 1988 AC unit, but this may help.

First off, the price of a new roof AC unit is a lot, and on your older camper, that also means the air box up in the ceiling has to be changed too as the new AC units do not work with the older style air boxes. So both the roof unit and the air box and controls all need to be changed.

From what I have been through on AC units, as long as the gas system (coils, compressor and gas components still work,) then the AC unit is worth repairing everything else compared to a new AC unit. When the gas system goes, then a new AC unit makes more sense.

Knowing the make and model of your roof unit and the air box system will help us help you better. We do not know if yours is still the original from 1988 or someone upgraded it along the way.

By your note, it seems the fan motor is what is giving you issues, is that right?

Going by a generic Dometic AC unit on a Sunline, (not knowing which model you have) the fan motor does have a capacitor for starting and they do die from time to time. The pics I'm going to show you are from a 2003 Dometic unit. Yours may be older and some things are different, but yours has something like this to make the system work.

The fan motor has two blower blades on the same long armature shaft. One
blade type fan is outside, you can see it with the cover off and the one you are most likely spinning by hand. The other blower blade is a squirrel cage fan buried inside the unit that blows the air inside the camper. You really do not want to change the motor unless you know it's bad as you have to take the entire roof unit apart to get the 2 blower blades off to get the motor out in the open.

The easiest thing to try first, in my view, is the starting capacitor for the fan. If you have an older analog volt meter, you can test the capacitor for basic operation to see if it have totally failed or has some level of life left. They do make special capacitor testers, but use the older volt meter helps get you started.

Again these pics are from a 2003 unit. I'm not sure what your looks like, but it has these parts somewhere. Posting pics of what you have will help more.

On the compressor side of the roof unit is a junction box with motor wires coming out of it and inside there are the capacitors. The silver box on the right side of this pic with the white wiring diagram on it. Your sticker may be long gone if you even have one.








Inside that box is a group of capacitors. There may be 2 of them or 3 pending if you have a hard start compressor capacitor.


On this unit, the big can capacitor is 2 capacitors in one. One to start the fan motor and one to start the compressor motor. The sizes of the capacitance is different for both.

The fan motor needs a certain size capacitor to run that winding motor. In this case, this fan motor needs a 5 MF (micro farad) capacitor to start it. Your motor label may or may not be readable.


Here is the double capacitor


On the bottom of it, is the label and ratings. The compressor uses the 30 MF part and the fan the 5 MF part of it


As I stated, the capacitor can be tested and or just changed. But, you have to get the correct one for the motor you have. This all starts with the part number of the upper roof unit, then a double check to what the old capacitor is rated at and it's part number, in case someone changed a motor along the way, as they do change the capacitor size sometimes when a new motor is installed. And if the motor label is still intact, what it says. Armed with that, then hunt for the Dometic parts.

The above does require knowing how to safely work around 120 VAC motors and controls. If you do not have this knowledge, then a electrician friend or and RV tech can help do all this for you. You can get hurt if you do not understand 120 VAC power.

If you are electrically friendly, then post the upper roof unit part numbers. inside the camper, up under the mesh filter, is a sticker on the bottom of the roof unit. That is the sticker you will need. We can help see if we can find the right part numbers, or take all this to a RV dealer who sells Dometic parts and let them tell you the right part numbers and sell you one.

This is what a 2003 roof unit sticker looks like


The last time I bought one of those combo capacitors, it was about $20, 10 years ago. Looking tonight, assuming the one for yours is still available, the prices range from #36 to $75 depending on what Dometic part number you are after.

The new fan motor I bought, again 10 years ago, was about $135. I'm sure with Covid price increases, odds are high they will cost more than that.

I did a quick hit on a new Dometic roof unit, the prices are all over the map. From $600 to $900 and some even more. And that is not the new air box and controls to make it work. For sure, try and get the fan motor to work.

Hope this helps

John
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Old 07-17-2021, 10:22 PM   #9
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If you want to post some pics to better help the casue,

There are 3 ways to add pics.

1. Upload pics to a specific post attaching them at the end of the post.

2. Linking them in from a public viewable web photo hosting service you have.

See here for 1 and 2 https://www.sunlineclub.com/forums/f...html#post86041

3. You can upload pics to the forum in your own personal photo album. Then link them to anywhere in the text of a post. See here on how to create an album. https://www.sunlineclub.com/forums/f...html#post87945

If you still get stuck, let us know. Pic's go a long way in helping show things you are working on.

Hope this helps

John
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Old 07-18-2021, 07:07 AM   #10
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I'll go with the cap. When the AC shuts off on normal cycle the compressor head pressure is at it's highest point. After the internal pressure drops it will start again. The capacitor is kind of like a "kick start" to over come the normal "body at rest" thing then add high head pressure you really need a good kick to get every thing moving again. By comparison a "cap" is cheap replace it just because you can.
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Old 07-18-2021, 07:53 AM   #11
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Now this morning I turned it on..fired right up..ran about 20 seconds and started to slow down and stopped..
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Old 07-18-2021, 08:41 AM   #12
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OK bigger issues then. Usually the cap is for starting only. Now obviously you are plugged in, a long extension cord can be a factor with voltage drop. The camper cord is pretty beefy but connected to a # 14 or less extension that plays a big factor in voltage drop there is a bit of science as the voltage drops the current rises making the problem worse. If you are directly plug in with the camper cord it should work fine. A clamp on current meter will tell the story pretty quickly. Kind of think it's time for an electrician if plugging it in directly doesn't work.
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Old 07-18-2021, 09:33 AM   #13
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It worked fine for 3 days.. continuously
I tried it with just the fan..not ac...same thing..blows about 20 seconds and dies slowly
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Old 07-19-2021, 11:08 AM   #14
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Quote:
Originally Posted by Buffetman View Post
It worked fine for 3 days.. continuously
I tried it with just the fan..not ac...same thing..blows about 20 seconds and dies slowly

Are you at home or in a campground? Low voltage and campgrounds with all the campers running the AC on a hot summer day is sort of a classic problem. If your camper voltage is low, motors do not like that. Power loads change by the day, hour and sometimes, minutes. When many of the AC units stop, then the voltage goes back up. I have a small plug in volt meter in a camper wall outlet just to see this problem.

If you are at home, are you plugged into a dedicated 30 amp RV outlet or on an adapter to a normal looking 3 prong plug that all the normal wall outlets are? If you are not on the 30 amp dedicated outlet, then other other power uses in the house may be on the same circuit as the camper trying to run the AC unit. And as was stated, the power cord size and length plugging in the camper is part of this low voltage issue.

You may have 2 issues going on. Low voltage and or a motor starting capacitor going bad at the same time.

If you have one of these volt meters plugged into the camper, it can help tell about the low voltage problem. https://www.amazon.com/Eversame-80-3...6714262&sr=8-5
I just found this one on the web quick, there are lots of different brands of them. I never used this one, mine is a lot more expensive and part of a power monitor that alarms for low voltage and other things that go wrong with campground wiring.

Give us some more to go on with how the camper is plugged in. We can only go off of what you tell us.

Hope this helps

John
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Old 07-19-2021, 03:48 PM   #15
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The best you can do in the camper is 20 amps unless some one went to the expense of installing a 30 amp outlet complete with #10 wire. It might scare people to know the adaptor rating is no better than a 20 amp circuit and some cheap one may do just 15 with out an over heat. The AC is on a 20 amp circuit inside the camper that's all you get. So if the microwave or the water heater or what ever is on too you maybe able to draw a fair amount of current It should run just fine on a 20 amp circuit. There is some thing beyond a normal problem as just the blower alone quit last time and it's current draw isn't that much. My concern is poor connections some where crispy wire connections are not a good thing.
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Old 07-22-2021, 12:34 PM   #16
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I'm surprised nobody suggested checking the motor for oiling ports at the bearing caps and/or shaft end. These DO get dry and the motor will start normally and die off within a minute or 2. Severe lack of lube can accelerate this to 30 seconds or less or it may mimic a capacitor problem. Oil the motor every season when you do maintenance on the roof unit (hose down/etc).



Check the motor for an oiling port around the center of the ends. May be a Red, white, or Black plastic plug (flattened golf tee shape). Remove it, and install some Zoom Turbine Oil(most ACE Hardware stores have it. DO NOT USE 3in1 oil (RED CAN!) In a pinch you can use straight 30W non detergent motor oil. Go Slow and add about 2 TSP (Teaspoons) per port. There is some felt that will soak it up, and the bronze bushings or ball bearings will soak up some additionally. Hand rotate for a minute or two to make sure it does freely and to make sure the shaft is fully coated! Then fire it up and see what happens.



It sounds to me more like dry motor bearings than a starting cap. I would investigate the motor and see if it has oiling ports, if yes add oil. After that if it still acts up get a capacitor. HVAC Parts houses usually have caps for AC Units that can be used. And generally they're cheaper than an RV Dealer.



Larry
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Old 07-22-2021, 07:35 PM   #17
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At a campground..just tried it again tonight..ran about a minute then slowly died.
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Old 07-22-2021, 07:37 PM   #18
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Going to open it up tomorrow morning..we shall see what goes on
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Old 07-23-2021, 11:44 AM   #19
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While you are looking, try and get a model number of the roof unit. Inside the camper, up under the mesh filter is the sticker, or at least is on the newer units.

By knowing the model, we can look it up and better understand what you have.

As FYI, the Brisk Air AC roof units from at least year 2003 and newer, (maybe even back into the 90's) have no oiling ports on the fan motor. It is a sealed double shaft motor with sealed bearings. The bearing closest to inside blower blade housing is totally inaccessible to even see the bearing. The bearing next to the outside fan blade, while it has no oil cup, you can try and squirt the shaft in hopes the something of the squirt reaches the bearing.



This is the exposed end of the fan motor. The rusted OD one is the original, no lube port




The bearing inside the motor.


If yours has sealed bearings, when they start to go you can many times feel a rough rotation of the shaft by hand.

Yours being older, might have an oiler, if so, try oiling it.

Take pics while you have it apart, that helps too.

Good luck, let us know how you make out.

John

PS, odds are high you do not have a walk on roof, so small sheets of plywood are needed over the rafters to spread your weight out. Just a heads up before you go up there.
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Old 07-23-2021, 03:22 PM   #20
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Not sure how to load a picture
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