Domestic sl135 roof top a\c on 1987 honey 421s rv. Unit has 2 capacitors and 1 relay now. Can I add a 2 supco spp6 hard start capacitor?

A thermostat or a relay activated by the thermostat turns power on to the capacitor for the compressor.

Hi, I did some research and found nothing on the a/c unit. If I had the model and serial numbers from the condenser and compressor this would help me. This would be a run capacitor doing the start up, dropping out the start relay and keeping it running. If you have only one run capacitor and its a dual, will have 3- female spades coming from the top, with marks that say Fan, C for common, and Herm. for compressor. If it has only one capacitor with2- female terminals, several places to connect more than 2 wires, its a single cap. If it just runs the compressor, it could be a 370 volt x 20, 25, 30, 35, uf?? If its a dual it could be a 370 volt x 5 u f for the fan and the same , 20, through 35 u f or microfareds. The best way to find out is to take off the wires on it, and make sure you draw a diagram so you know they are right, and take it to a appliance parts house and let them check it to see what they are. Larger units can have a 440 volt x 20 to 35, 40, 45 and so on. Your unit is not that large, so it will only be 370 volts as far as voltage, but the u f value will need to be checked with a meter that will check the value of these and give you a number such as 4.99 u. f. and you will no its a 5 u f. It may be higher like 5.24 u.f.and that is OK. Make sure the capacitor has no oil leaking from it or its not swollen looking or distorted in anyway, it will be open or shorted out. Please let me know if I have been of help to you when you go to rate me, please be kind. I will be here if you need my help if you are having problems with the compressor not starting.
Sincerely,
Shastalaker7
A/C & Heating Contractor
PS If this capacitor is black plastic and mounted on the side of the compressor, it will be a start, run capacitor with 2 wires. It snaps in a metal type holder you will need to take it out and check the terminal area it was connected to and remove it. If only 2 wires, it won't make a difference what side the leads hook to.

It could be the capacitor, it could be a loose wire connection, it could be a delay switch or a contactor/relay.

check the condensor fan in the rooof unit. It's the fan blowing on the cpil on the roof.. If it failed, the head preasures can becme excessive andwork the compressor hard causing the breaker to trip. Let me know and good luck, Ned_

If it has a start capacitor the papper hole in the top of the start capacitor
will be broken if the capacitor was shorted I would have the run capacitor frist But if there is not a burnt wire then the compressor may be bad. You can try a hard start kit that pulgs on the two terminals of the run cap to see if the compressor will start but you will need a amp meter to tell if the compressor will continue to run

Yes. Use all the replacement parts. Your compressor is hard starting due to increased tork and wear. That is what burned out the original cap.

No, the units are sealed and the rain should not have affected the system at all. I would remove the outer cover of the unit and access the capacitors. Your start capacitor may be bad. You can visually inspect this and tell if there is a problem. Small black relay on top of capacitor often burns out, if so, replace capacitor and relay. If this looks fine, then we need to start at the thermostat and work our way forward.

Thanks,

Jeff

Hi, If the 3 posts are top center and bottom right left, the black wire goes top the top center post. The red wire will go to the bottom right and the white goes to bottom left.
If the posts are bottom center and top right left, the black goes on bottom center and the red goes top left. The white goes top right.
If you do not see a capacitor, disregaurd the wires in the 3-1
I hope this helps you. Please let me know if I can assist you further.

Vic

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.

I Had a similar problem with my Air Conditioning unit, the repair man said without the information their was nothing he could do, but that he would go look for it.

This is what i was able to find, This litterally all just took place within the past hour so i don't know if its workable information, but here is my two and a half cents.
http://www.transtaracsupply.com/pdf/s3ba.pdf