Originally Posted by Buffetman
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