AC Units, to replace or not to replace, that is the ?

[Doc Vegas]

Greetings: We just returned from 5,000 miles (7 weeks) on the road. Good trip overall, despite numerous failures on the rig. We are back in Arizona and the temps are still hot. It seems my AC units have lost their spunk and can barely keep it cool. The rear unit would not even fire up unless I turned off all other applicances (I got 30 amp sadly). I am wondering if after 10 years, if it best to replace at least one of them...? I read as much as I could find on-line and it sounds like after 10 years, they are usually replaced (other than the capacitors). Curious to get some opinions from the pros on here. Is there a temp that should be coming out of the registers? I cleaned out both units before the trip and both were VERY clean from the top side. The inside exchanger probably needs cleaned as the filters got very dusty within a week or two consistently. Would appreciate some advice as I am planning to move to a DP within 1-3 years. Thanks!

[jacwjames]

I would try cleaning the evaporator coil before doing anything. Not an easy job. I had to replace a motor on my front AC a couple years ago and while I was doing that I took the time to blow out the evaporator.

After I took the shroud off I had to take some screws out and peel back the sheet metal. This gave me access to the fan that I had to remove from the shaft of the motor. While it was apart I used a blow gun to blow the coil out.

Also blow out the condenser coil.

See if this helps and if doesn't then consider replacing your AC.

[mchero]

Originally Posted by jacwjames

I would try cleaning the evaporator coil before doing anything. Not an easy job. I had to replace a motor on my front AC a couple years ago and while I was doing that I took the time to blow out the evaporator.

After I took the shroud off I had to take some screws out and peel back the sheet metal. This gave me access to the fan that I had to remove from the shaft of the motor. While it was apart I used a blow gun to blow the coil out.

Also blow out the condenser coil.

See if this helps and if doesn't then consider replacing your AC.

Evaporator coil easy to clean if you know how to propery get to it via ABOVE, not from within the coach. Most AC units you can remove the shroud on the topside.

Replaced after 10 years?

If maintained properly they can outlast the coach. I owned a 93 Pace Arrow Diesel Pusher. Sold it 2 years ago. To this date still has original;
Furnaces (2) with original ignitor boards.
Hot water heater with original ignitor board.
Roof AC units.

The rooftop AC/Heatpumps on our current rig nearing 10 years and still cooling well.

[Lt Dan]

Originally Posted by Doc Vegas

Is there a temp that should be coming out of the registers? I cleaned out both units before the trip and both were VERY clean from the top side. The inside exchanger probably needs cleaned as the filters got very dusty within a week or two consistently.

Measure the air temperature going into the intake on the AC. Then measure the cold air coming out. A twenty degree drop in temperature from the ambient is about all you can expect. Cleaning the evaporator coils on the inside is a good idea and might help with air flow and temperature drop.

[deandec]

Just replaced one 21 year old roof AC. Other is still doing fine.

Mine did not hear about the 10 year replacement idea.

Air temp from cold air duct should be about 20 degrees lower than room temp.

Two roof AC's on 30A means very little power left over for other appliances.

Try not to start both AC's at the same time.

Keep the return air filters clean.

Be sure that the cold air duct does not leak into your return air duct. (they are close together in a roof AC) If it does, the AC may think the temp has been attained.

Be sure and AC duct is not blowing on the remote thermostat.

[spyderRV]

My last camp out everybody was running full A/C. The pedestal showed 109 volts with one A/C on and 101 with two, if I could even get the second one to start. I was worried that the low voltage would damage the motors, so I fired up the generator, MMMMM 126 volts, so I cooled off the RV with the two A/C's than switched to one without the generator. I got one of these after reading about it in another thread.

DROK Flat Plug AC 80-300V Voltage Panel Power Line Volt Test Monitor Gauge Me...

[Gary RVRoamer]

I don't subscribe to your 10-year replacement theory. A/c units generally work or they do not. Yours should be dropping the air temperature through the unit by 20-25 degrees, measured in the air at intake and outlet. If it is, they are good. If not, the question is why? Could well be dirty heat exchangers, inside or out.

The one that won't start reliably may have a start capacitor problem, but that doesn't usually depend on turning off other appliances. I think it more likley that yu may have corrosion or broken wires in your shore cord, or a bad shore outlet, and you are not getting full voltage & amps into the RV.

[Doc Vegas]

Wow, thanks guys!!! I really do not want to replace these as I do not plan to keep it that long. I read about the 10-year concept from a link on Google, just said if they are failing and over 10 years old, replace. Again, I do NOT want to replace them.

On the cleaning, I did remove the shrouds and cleaned the heat exchanger on the roof units. But, what is the other one you guys are talking about? Is it the one I get to inside the rig (under the air filter???)? If so, yes, those look a bit dirty. I figured I would hook up a shop vac with a brush attachment. Any other ideas?

Thanks again!!!

[UncleBilly]

Mine are 20yrs old and original too the rig. I've measured cold air in the high 40's coming out. Not kidding 😜👍🏻


1996 Country Coach Intrigue 😜

[TQ60]

First get a copy of the manuals for your units and read the maintenance section.

Get an ir thermometer and a dial on stick one too if yiu can find one.

Do pre and post measurements on each "single step" you do.

You need to confirm how units are working then do an action and measure the results so you can be sure of your efforts.

Also note that ambient temperature makes a huge difference.

The outside temperature is how the heat is removed from condenser or outside coils so the inside temperature drop across the evaporator or inside coils may be less on a hotter day so consider that when comparing your notes.

A few things.

Air flow is critical so fans need oiled bearings for full flow and coils need to be clean and nit mushed together.

Often outside ones are squished together and a comb is used to straighten them.

Check air flow if ducted.

Often ductwork restricts air flow which reduces cooling.

There is a sensor in the evaporator that shuts compressor off if it gets too cold.

If air flow is slow then it gets cold and shuts off compressor.

More air flow transfers more heat and keeps it from doing so.

You can use a match to create a smoke trail or use a computer fan connected to a voltmeter to measure air flow.

Many have leakage between in and out flows that result in cool air not flowing into the cabin.

Many things to tinker with

[mchero]

NICE writeup TQ60!

[TQ60]

You are welcome.

Many things learned over time and most as a result of units that support communications sites.

One site had the unit that monitors the evaporator temp fail so it would not shut compressor off which does not seem too big a deal until filter starts to restrict air flow so the normal condensation that drips off gets frozen to the evaporator resulting on the total unit turning into a huge ice block as the equipment is still generating the heat so ac stays running.

Nothing like hiking into a snow bound building and digging snow from front of door with no snow touching building and opening the door to a 140 + heat. (Thermometer pegged at something above 140)

[Starsekr]

Doc,. Desert AC is a little different. As outside air temps increase, up into the desert 105-115 F we have been having, the AC isn't as efficient; the motor compressor has to work a lot harder because the refrigerant pressure is higher and the outside air through the condenser is hotter, so the motor draws more amps, gets hotter, etc. AC units in the desert are just punished more and have a higher failure rate. That said, the temperature difference method quoted above is a good way to keep track of your AC performance. If you have an energy center/amperage monitor that is another good tool. A compressor rated at 9 amps at 80 degrees outside will draw 11 or 12 amps at 110 degrees. Because there is a pressure differential across the compressor after it shuts off, there is minute or two time delay to allow the pressure to drop before it restarts. This delay is usually long enough for normal environmental temperatures but might not be for the desert. Give it about 5 minutes before a restart if you can.

[slowmachine]

I believe that the "10 year rule" is likely to be valid in one context. When I see the parts/labor cost of repair rise to around half of replacement cost, I begin to seriously consider replacement instead of repair. This is especially true in cases where I can perform the replacement without professional assistance, but don't have the time, tools, or skills to perform the repair.

With appliances of all types, 10 years seems to be a common replacement age. If I'm planning to keep using it for another 10 years, I usually buy a new one. We just finished this cycle with our home appliances (two kitchens plus the laundry) which were all replaced in the 9-12 year age window, as they began to fail and need repair. Newer models are most often more efficient, and parts support for the old ones is often poor.


Mike
2000 HR Endeavor