Carrier A/C Compressor making a humming noise

[CLIPPERGUY]

The Carrier A/C on my 2006 Jayco Greyhawk is making a buzzing noise. I'm getting ready for a trip and afraid my a/c may go out in the summer heat.

Carrier A/C model is 68RV15102A

Here is a video of the noise.

[j-d]

While you were up there, did you get pix of the Capacitors and the Wiring Diagram?

An A/C may have

As few as ONE,
Probably TWO, and
Likely THREE,

Capacitors.

Only a Compressor Run Capacitor
Compressor Run and Fan Run Capacitor (could be individual or a combined unit)
Two Run Capacitors plus a Start Assist

Start Assist is a Capacitor plus a device to get it OUT of circuit once the Compressor starts. Think of that as the starter in a car. The Key has to be released, from Start to Run when the engine starts. Compressors with Start Assist have to get that component off line to get into RUN mode.

I'd like to see Diagram AND a Pic of the actual capacitors because Start Assist can be an option that's shown on every Diagram but not installed in every Unit. You also need to get the specs from the Capacitor(s) if you plan to replace one. We've had enough capacitor trouble with out home A/C that I keep spares at the house. I also have spares and spare start assist for the RV A/C, based on the issues at home and several OP's here mentioning failures in their RV's.

You can replace a Combined Compressor + Fan RUN capacitor with two individual ones, replace two individuals with a Combined, use only one side of a Combined, etc. The capacitance (40-MFD as an example) and voltage (probably 440, maybe 370 and you can replace a 370 with a 440) are the two specs you need to match in replacement capacitors.

Your neighbor can explain safety in working with electrical components, and capacitors in specific.

[CLIPPERGUY]

My neighbor came by but he was not very much familiar with RV air conditioners. He used his wrap around gauge to measure flow to the compressor. He said the electrical flow was good and perhaps the bearing are bad in the compressor.

I've re-read the feedback provided and I'm leaning toward testing/and replacing the capacitor but it appears that it's function is starting the compressor as oppose to running it.

Thoughts?


Here is the manual for my ac. It contain the wiring diagram and other info. I have the Standard Unit

http://www.transportaircon.carrier.com/Files/AirV/Local/US-en/customer_service/99-00469-00.pdf

[CLIPPERGUY]

Funny you mentioned leak from rust. While looking at the unit, I noticed that water is accummalating at the rear of the unit where the fan turns. I don't see a drain but will look closer and drill a small hole to allow drainage if a drain port doesn't exist.

At any rate, while the compressor is on, I noticed what look like bubbles from the pool or water. I attributed it to the fan turning becuase the pool is at the base of the fan blade. I neglected to turn off the compressor and see if the bubbles still appeared. I'm going to do that before he comes to see if I have leak in the system. That may save him some troubleshoot time.

I suspect if there is a leak it wouldn't be cooling and the freon would have leak during a single use. I noticed the noise a few trips back.

I will report out the results

[j-d]

Even better! Please let us know the process used and the results found.

Be surprised if he says "compressor" but ya never know. Central systems have service ports where a tech can attach gauges, but "room" units, home fridges, etc. do not. They're sealed upon assembly with a "lifetime charge." Which is about true. Barring damage or rust/corrosion, there's little chance for the charge to get away. There are "Saddle Valves" sometimes called "Bullet Valves" but experience usually show they create leak points.

Commendable you want to quiet that A/C even though it may be working.

[CLIPPERGUY]

Thanks again for the feedback.

I have a neighbor who is a a/c guy. He going to come by this evening to check it out.

[CLIPPERGUY]

Excellent feedback on troubleshooting. Thank you so much. I do have meter from Harbor Freight as well.

I will post picks as requested.

[j-d]

If we've noticed one thing about RV A/C failures:

It's RARELY the Compressor! Most failures stem from:

Dirt,
Controls,
Capacitors,
Refrigerant Leaks

Dirt and Capacitors are easy fixes.

Controls can be tricky, but

Refrigerant Leaks and Compressor Failure usually mean "Replace the A/C Unit" at least for most of us.

Your A/C is 2004, but ten years isn't senior citizen age for the Sealed System (Compressor, Coils and Tubing) in an RV A/C.

We had an OP who worked in A/C on Boats. Thinking of it, Window Units, Boats, and RV's all use A/C of about the same capacity with similar components. In Boats the Condenser is water-cooled vs. outside fan in the others, but Compressor is likely to be similar. He pointed out cases where the Motor portion inside the Compressor Shell had separated from the Compressor portion inside there. In those, you'd hear the Compressor "Running" but no cooling. But that could also happen if the refrigerant had leaked out OR the valve(s) in the Compressor had gone bad.

Do you have access to an AC (alternating current) clamp-on Ammeter like this?
I picked a Harbor Fright item because they're cheap, I could find a photo, and I have one that's been very useful.

Compressor should have a plate or label showing two or three amperages:

"Start" (which many clamp-on's can't report since the compressor shifts into Run so fast)

"LRA" (Locked Rotor Amps) which is when the motor portion can't turn

"Run" which is what a normal compressor, proper refrigerant charge and supply voltage, should draw

You don't have LRA, at least yet. If you ever do, compressor or capacitor bad.

If RUN is Low, Charge could be low, or Valve(s)weak.

If RUN is High, Motor Bearings/Compressor Pistons dragging.

A Compressor Run Capacitor (which all A/C's have) of the wrong value can cause compressor overheat. Hot compressor could have high Run Amps. If you want to get into Capacitors, remove the access cover if you need to, and post a photo of them. Many compressors also use a Start Assist Capacitor and some form of device to cut that compressor out once the unit starts. Photo'd help sort out what you actually have.

OH!!! You may see a Wiring Diagram. Photo that too.

[CLIPPERGUY]

Running the a/c on generator and shore power produces the noise.

I havent checked the voltage yet but will.

Thanks for the feedback.

[j-d]

Read above reply more carefully. Capacitor is only a guess and I don't have much confidence that a failing capacitor would make the compressor noisy. Was Voltage OK? If you're running the A/C at home on a 15- or 20-Amp circuit and/or standard duty extension cord, you could easily have low voltage to the compressor. Still, we've had low voltage and the compressor didn't get loud. Just tripped the breaker.

[CLIPPERGUY]

Yes it is cooling and airflow is normal. I can only hear the noise from the outside. It slightly annoying and I don't wish to disturb any neighbor while at a campground

[CLIPPERGUY]

The noise starts when the compressor kicks in. No noise when it is fan only.

The noise is coming from where the small container connects to the larger compressor tank.

To eliminate bad damper feet, I shook the tank to make sure the noise wasn't coming from the base.

I used a hose up to my ear to locate the source of the noise.

I have no experience with capacitors or the like. I'm pretty handy but prefer not to mess with electricity, if I can help it.

[j-d]

I take it you tried the Fan Only settings and no humming sound then?

It IS cooling, right? Air flow seems normal?

You can run the compressor BRIEFLY with fan disconnected and confirm the noise. Are you sure the outdoor fan blade and inside blower wheel are tight and undamaged?

We had a Coleman that made noise because one of the shock mounts at the base of the compressor got out of place.

Noise also possible if refrigerant lines get to rubbing, against each other or against the cabinetry.

I don't know if a failing capacitor can get the compressor out of phase enough to make noise but capacitors are cheap.

Have you worked on 120VAC equipment? And with Capacitors? If you haven't you'll need some coaching and a Helper/Safety Observer.

Two suggestions:

1. Update this thread with Model Number of the A/C. Maybe we can find a wiring diagram to show how to temporarily disconnect the Fan, and how the Capacitors are connected.

2. Click "Notify Moderator" and ask to move the thread to Tech Issues. This A/C is used by all RV types, and more techy OP's hang out there.

[RoyB]

Have you checked the 120VAC VOLTAGE. Being too low will cause that...

[CLIPPERGUY]

It's the compressor

[Toddupton]

What is humming the fan or compressor?