Original dometic ac replacement options

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Original dometic ac replacement options

July 05, 2018, 10:52:43 am

My rear roof ac wasn't working on the weekend. We made it through on the front one. I have tested the capacitors and they are ok but the compressor is not running so it looks like a new unit.

Will a new dometic unit still hook up and work with the thermostat from my old unit? If not can I at least reuse the cable?

I need to keep this simple we are headed out again in two weeks.

Thanks

Re: Original dometic ac replacement options

Reply #1 – July 05, 2018, 11:00:46 am

Toby,

Before you give up on this one did you check the compressor start relay? If it is bad the compressor won't start. Here is the Dometic number for our A/C unit 3311547.000 it is pretty much a standard part. This won't help if the compressor is locked up or has a burn't winding internaly. (you can check the windings with an Ohm meter)

Mike

Re: Original dometic ac replacement options

Reply #2 – July 05, 2018, 11:14:22 am

Agree - check everything before replacing. But, if you DO have to replace, here's my experience on our 1996:

I replaced both units with new Dometics, and had to replace the original 4-button thermostat with the (then) newer 5-button one. That all worked fine.

However: I recently experienced a friend's coach with new Atwood units, and they are much quieter than mine. I think you can find discussions here about them; I'd suggest you consider them instead of the Dometics. His had remote controls for the ac units, and you'd still use your existing thermostat for your furnaces I think.

Re: Original dometic ac replacement options

Reply #3 – July 05, 2018, 12:31:40 pm

We used the Atwood unit to replace the Dometic. Much better. You do not use the existing thermostat as the unit runs continuously on low and senses the temperature which you set on the unit or with it's remotes.

Keith

Re: Original dometic ac replacement options

Reply #4 – July 05, 2018, 01:00:04 pm

Keith what size Atwood A/C did you buy? I see they list their 13.5Kbtu as equivalent to a 16Kbtu on other brands.
Have you or anyone else experienced that the Atwood 13.5 actually cools better than other brand 13.5s?

Re: Original dometic ac replacement options

Reply #5 – July 05, 2018, 01:11:07 pm

Thanks for the info. My diagram doesn't show a start relay only the run and start capacitors and a ptcr. I can't blame it for packing it in at this age. I have found a seller of scrathyand dent units for 500 plus 125 for the inner panel I will see what he has.

Re: Original dometic ac replacement options

Reply #6 – July 05, 2018, 03:02:51 pm

Toby,

Yours must have the relay that is mounted to the PC board. Now this is from memory but on that print it should be a little square in the lower left side of the print. Yes it can be replaced but I don't know that number off the top of my head. Now one other thing you need to check out, there should be a little fuse on the PC board, check to see if it has came loose or is blown.

Mike

Re: Original dometic ac replacement options

Reply #7 – July 05, 2018, 04:30:36 pm

I replaced my front A/C a couple years ago with the Atwood 15,000 unit and was very happy with it.
Last week I replaced the bedroom unit with the same 15,000 unit. I went with the 15,000 btu units because they offer the heat pump.
As stated, the Atwoods come with a control unit that hinges down off the A/C inside cover, there is also a very small remote to control the units.
These control options are good for me, I don't miss having to use the wall mounted controls.
I bought the newest Atwood from the 12v Store. Turns out they are local and I was able to pick the unit up at the warehouse and avoid almost $100 in S&H costs.

Re: Original dometic ac replacement options

Reply #8 – July 05, 2018, 05:57:11 pm

We did the same as Lon, 1500 unit.

Keith

Re: Original dometic ac replacement options

Reply #9 – July 05, 2018, 06:31:46 pm

Is the pc board located on the inside half of the unit?

Re: Original dometic ac replacement options

Reply #10 – July 05, 2018, 06:55:24 pm

I'm curious, how do these Atwood AC's hold up?
Mike

Re: Original dometic ac replacement options

Reply #11 – July 05, 2018, 07:08:42 pm

Quote from: its toby – July 05, 2018, 06:31:46 pm

Is the pc board located on the inside half of the unit?

Toby,

No you have to take the outside cover off then there is a metal side cover that you have to remove then you will find the board. There should be a capacitor or 2 in there also.

Mike

Re: Original dometic ac replacement options

Reply #12 – July 05, 2018, 07:10:26 pm

Going to have to look further. I accessed the capacitors but didn't notice the board.

Re: Original dometic ac replacement options

Reply #13 – July 05, 2018, 08:39:43 pm

Quote from: its toby – July 05, 2018, 07:10:26 pm

Going to have to look further. I accessed the capacitors but didn't notice the board.

Toby,
That is where our P/C board was on our '92, in the same area as the capacitors. Ours had the remote relay though so yours must be somewhat different.

Mike

Re: Original dometic ac replacement options

Reply #14 – July 05, 2018, 09:18:51 pm

If you buy new Dometics, can't you use the old boards in the new ac's?
John M.

Re: Original dometic ac replacement options

Reply #15 – July 05, 2018, 09:39:53 pm

Keith,

When does the Atwood run continuously? While it would be nice to move air all the time and just cool when needed, doesn't run all the time seem a bit too much, and just add sound and maybe wear. Even a low sound level could be annoying after a while? Does motor ever shut off in cool mode?

Is there a mode that only runs when calling for cooling? Our current 20-yr OEM units run all the time on low, med or high, but only run when compressor runs if fan is on auto. Does Atwood have a similar Auto mode?

What other features do you like about Atwood? And disadvantages?

Re: Original dometic ac replacement options

Reply #16 – July 06, 2018, 09:18:44 am

I don't know about the Atwood, but I have carriers in a 5th wheel they are tied into the same duck system. If you do not leave the fans running when one unit is running the cold air makes the other unit think it is cold in Rv and not start, even if temp in Rv is 95+

Re: Original dometic ac replacement options

Reply #17 – July 06, 2018, 11:47:40 am

Quote from: Barry & Cindy – July 05, 2018, 09:39:53 pm

Keith,

When does the Atwood run continuously? While it would be nice to move air all the time and just cool when needed, doesn't run all the time seem a bit too much, and just add sound and maybe wear. Even a low sound level could be annoying after a while? Does motor ever shut off in cool mode?

Is there a mode that only runs when calling for cooling? Our current 20-yr OEM units run all the time on low, med or high, but only run when compressor runs if fan is on auto. Does Atwood have a similar Auto mode?

What other features do you like about Atwood? And disadvantages?

The Atwood has separate motors for condenser and evap fans unlike Dometic units that use a single motor for both. The evap fan runs continuously and is pretty dang quiet in low, a little less so in medium, and somewhat loud in high speed. Still quieter than my old Penguin in all speeds. The Atwood has an auto mode that keeps the evap fan in low and then cycles through low-high depending on what it thinks you need for cooling but the evap fan never turns off unless you turn the unit completely off. I had similar concerns about the fan running all the time before I bought it but I've not found it to be a bad thing in actual use.

The condenser fan comes on and off when needed and can be heard over the sound of the evap blower in low when laying in bed at night, for example. The overall noises made by the Atwood are far less annoying than the Penguin to me. Moreover, replacing a 13.5k Penguin with a 15k Atwood allows me to run only the rear roof air to cool the entire RV the vast majority of the time due to the increased airflow of the Atwood.

The Atwood is not low profile like the Penguin so it looks like a big lump on the roof in comparison. It is built incredibly well compared to the Penguin. I wouldn't even consider going back to a Dometic unit after having used this thing for a month. I just wish they would bring the variable speed inverter driven Dometic Harrier to the US that the Aussies get.

Re: Original dometic ac replacement options

Reply #18 – July 06, 2018, 02:33:12 pm

To add to the above the unit is used commercially on the Melbourne tram (streetcar) system. It looks a lot better built than the penguin.

Keith

Re: Original dometic ac replacement options

Reply #19 – July 06, 2018, 05:34:27 pm

Thanks Robert, I am aware of the separate condenser & evaporator fan motors.

Is there is mode that keeps the evaporator fan off until cooling is called for? That is instead of running at low speed.

Re: Original dometic ac replacement options

Reply #20 – July 06, 2018, 06:43:25 pm

No. The evap fan runs continuously unless you turn the whole unit off. It isn't a deal breaker for me but I've read a few reviews that said it was for them. Maybe somebody could rig something up to create the situation you want.

Re: Original dometic ac replacement options

Reply #21 – July 06, 2018, 06:50:36 pm

OK, lets look at what happens with a "constant run" evaporator fan:

It runs (as it should) when cooling is needed. It continues to run when cooling is not needed. When that happens, the water that has condensed on the evaporator (YES, this is very important in humid climates, not so in dry ones) is then returned to the interior as the fan blows air over the WET evaporator.

Not sure this works for humid areas. Please convince me.

Re: Original dometic ac replacement options

Reply #22 – July 06, 2018, 07:21:55 pm

I understand your issue but haven't found it to be a problem in real world use. I've been in Missouri since I got the Atwood and haven't had any issues with humidity with it running nonstop. We've had a couple of days recently where it rained all day and cooled off enough that the AC didn't run much but no excessive moisture. There is a DRY mode which provides a dehumidifier function if needed.

Re: Original dometic ac replacement options

Reply #23 – July 06, 2018, 07:29:10 pm

Quote from: wolfe10 – July 06, 2018, 06:50:36 pm

OK, lets look at what happens with a "constant run" evaporator fan:

It runs (as it should) when cooling is needed. It continues to run when cooling is not needed. When that happens, the water that has condensed on the evaporator (YES, this is very important in humid climates, not so in dry ones) is then returned to the interior as the fan blows air over the WET evaporator.

Not sure this works for humid areas. Please convince me.

Brett, believe you are correct, the water on the evaporator coil will now evaporate and be recirculated through the coach. But, only to a degree, and not enough to make a big comfort difference. I normally run my ac fans on low all the time so they never shut off. Just checked my hydrometer/thermometer in the coach. Temp was 82, humidity 33%
Outside temp. 92, humidity 78%

Re: Original dometic ac replacement options

Reply #24 – July 06, 2018, 10:57:41 pm

Quote from: its toby – July 05, 2018, 01:11:07 pm

Thanks for the info. My diagram doesn't show a start relay only the run and start capacitors and a ptcr. I can't blame it for packing it in at this age. I have found a seller of scrathyand dent units for 500 plus 125 for the inner panel I will see what he has.

The scratch and dent units from adventure RV are total toast, a friend bought 2 and they look like they fell off of a shelf about 20 feet up. He has had no luck returning them.

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