Today's Coleman Mach 15 Incident

[j-d]

We're right on a beach in FL, temp in the upper 90's with high humidity, bright sun and no shade. Our A/C had been keeping the coach on the warm end of the comfortable range, around 80. Till this afternoon. It'd run 10 minutes, compressor shut down, need 20 minutes to recover on High Fan Only, then run another 10 minutes. I went to the roof to do two thingd:
1. Verify that the Evaporator and Condenser Coils I'd recently cleaned, were still clean.
2. Test and possibly Replace the Compressor RUN Capacitor. This is a 40 uF capacitor, and I had a new spare. Old (from 2002) capacitor read 36 uF on my Fluke 12. New read 40. I don't think 10% off spec is too much, but I installed the new one and buttoned the unit up.
It has run since, blows colder, and sounds better. I can only figure the capacitor has gotten "tired" without total failure. It isn't swollen or leaking.
VERY glad I had a spare!

[time2roll]

j-d wrote:
This reminds me of testing TV Tubes with my dad as a kid. We'd go to (drug store as I remember, can that be right) and use the Tube Tester.

Yup the drugstore. This is also a childhood memory of mine. 😉
Sometimes it worked, sometimes you take it in, eventually you just get a new one. Very expensive compared to today.

[j-d]

I plan to try the "baking test" on the failed capacitor, not done yet.

I also have not gone back to the roof to see how the new one is labeled. The BOX says "IEC 252 Class B Reliability" and "Assm in Mexico."

Can't find the IEC-252 spec on gOOgle, but it seems the premium spec is EIA-456-A with 60,000 hour reliability.

The one I installed, ordered on Amazon is a Proline Brand, and IEC-252 as noted. I plan to get another capacitor to carry as spare. So far I've found Genteq, formerly GE, that's IEC-456-A. If it's actually a higher spec, I'll install he Genteq and drop the Proline back to onboard spare status.

I'd love to hear from anybody with details on these specs. I do know that I had a couple home HVAC capacitor failures and took a failed one to a different parts house. Countergirl said the one that failed had a much lower hours rating than the line they carried. And their price was LESS!

[down_home]

Our units at home have a run start capacitor. They also have provision or another capacitor, if hard to start, if needed. I don't know at this moment what the capacitor requirement is on our mh units. They installed a higher rated cap, last time.

[allen8106]

TenOC wrote:
I am not sure . . . :S . . But I think the Capacitor is only "used" to start the compressor. After the compressor is running, the capacitor has no effect. May be a real electrical engineer can verify.

Some AC's come with a duel purpose start/run capacitor.

[down_home]

The company that services our appliances, is great, and at our door within hours i not minutes. Just had to replace the motor in one o the house units.
Earlier this year we had another Capacitor replaced.Three or four in the alst several months. Only paid for two.
He stated that capacitors are now the number one reason or call outs.
They are all made in China.
He bought a supply of them necessary in his business, marked product of USA.
He showed me two capacitors,the one marked USA and the one he took off, marked made in China. Identical in every detail.
Where I buy our air conditioner filters, which are out sized. I asked him the difference between the two he stocked. He said about 10.00.
They stock and sell all kinds of AC parts and units to Installers or anyone.
I was told they use very thin treated paper or plastic, I have forgotten, in construction to cut costs, in China.
So your antique American made capacitor is made to last a lot longer.
Nothing worse than,the heat pump going out at 11:00 pm and it ninety degrees or, ten below but a great income for Producer and and importer and reapirmen, for what appears to the universal source.

[wa8yxm]

You have described ICING synptoms rather well

Many A/C's have a sensor stuck (hopefully) in the evaporator coils. THis is a "Frost" sensor. if it senses the think icing up it will shut down the compressor.. Some work better than others and of course that old Realator's line "Location, Location, Location" is all important. Some are where they sence icing swiftly and swiftly shut down the Copressor so 3 or 4 minutes later it's ready to try again, Others take a bit longer and then ice needs to melt.

But you have described Cycling due to ICING..

OF course. OTHER causes are possible but you mentione both heat and humidity in the 90's and that can ice 'er up.

[j-d]

Thumb wrote:
The start capacitor is only in the circuit during start up, then is automaticaly disconnected

The run capacitor stays in the circuit as long as the compressor /fan motors are running

Yes. Compressor and Fan in these RV A/C units are "PSC Motors" and I looked up this definition:
***
A permanent split capacitor (PSC) motor has neither a starting switch, nor a capacitor strictly for starting. Instead, it has a run-type capacitor permanently connected in series with the start winding. This makes the start winding an auxiliary winding once the motor reaches running speed.
***
In the RV A/C units, this means TWO RUN Capacitors, one for Compressor and one for Fan. If there's also a START Capacitor, it supports only the Compressor.

Our Mach 15 has a START Capacitor connected to the Compressor RUN Capacitor. It's controlled by a "Potential Relay" which I'm told provides better management of the Start Cap than the less expensive PTCR device (like SUPCO SPP6 has) and even the "electronic" versions (like SPP6e has), so I left it in place. FYI, in addition to the spare RUN cap, I have an SPP6e aboard as a spare Start Cap. "Start Assist" is probably the better term, since it's a Cap Plus a PTCR, Relay or Electronic switch.

@SVCJeff - YES, I suspected Frosting too. So when it was in its failed state, right after quitting, I had my tools in a bucket ready to go. Bolted for the roof and pulled the Shroud then Evaporator Cover. Clean and dry. From there, jumped into the Capacitor.

@GordonThree - I left the OEM Compressor Run Cap in place and moved the wires to the HERM (Hermetically Sealed, meaning Compressor) terminals of the two-way spare I had. Didn't connect FAN, and left the unit that way. When I get home, I'll clean that installation up by removing Old and securing New in place. When I do, I'll warm the Old and test it again.

This reminds me of testing TV Tubes with my dad as a kid. We'd go to (drug store as I remember, can that be right) and use the Tube Tester. Call the TV Tech when we couldn't find the problem. He had a caddy packed with new tubes, and one of those usually fixed it when our old one tested good. Name was Roy Ong and Roy explained that Testing and Using were two different things.

EDIT: This A/C does not have a Wall Thermostat, so NO Frost Sensor. That makes Freeze-Up a real concern. We have to run on High Fan all the time or it will frost over. Just wasn't the case this time...

[Thumb]

TenOC wrote:
I am not sure . . . :S . . But I think the Capacitor is only "used" to start the compressor. After the compressor is running, the capacitor has no effect. May be a real electrical engineer can verify.

Hope this helps,
The start capacitor is only in the circuit during start up, then is automaticaly disconnected

The run capacitor stays in the circuit as long as the compressor /fan motors are running

[SCVJeff]

And it wasn't iced up? All the symptoms are there mebbe with the hard start cap in trouble as well

[ScottG]

The other thing about testing caps with any kind of tester is that they don't get the high voltage they see in actual use.
They will slowly break down internally as they age and temperature cycle.
While it may only come into play to start the compressor or fan, if they short or even soft-short at any time they will cause problems.

[TenOC]

I am not sure . . . :S . . But I think the Capacitor is only "used" to start the compressor. After the compressor is running, the capacitor has no effect. May be a real electrical engineer can verify.

[j-d]

That's sorta what I was thinking. Breaking down hot. Definitely reduced the effectiveness of the compressor. A/C is quieter inside and outside the coach than it's been for awhile.

I'd like to connect the FAN side of this new Capacitor too, but it's confusing to me. The original ones are two separate capacitors, but there is no jumper between them to serve as a COM terminal like the new two-way capacitor has.

[GordonThree]

I bet if you put the old cap in an oven and warmed it up to 150F and tested again, you'd find it was more than 10% out of spec.

Glad to hear it was a quick fix for you!