A/C tech question

EMD_Driver · 07-12-2011, 06:08 PM

I took the Dometic/Duo-therm unit I got to an appliance repair shop, so I could get the refrigerant checked yesterday. The guy tol me that he could run the A/C without the control board, or thermostat. He said that he could simply jump the white and black wires, to run the unit for charging.

This afternoon, I get a call from them and was told that the compressor is bad and they were unable to charge it.

Not being technically proficient with these units, I would like to know if it's possible to do what he said he could. Could he have destroyed the compressor?

I have the control/relay board and thermostat and plan to hook it up, when I go back. I'm curious to see if the unit works, when it's properly hooked up.

Gene · 07-12-2011, 07:22 PM

Doesn't sound quite right. Maybe apply 110/120 volts to white and black...

Here is the diagram from my 579 series book. The control module is on the left of the picture and the compressor and fan on the right.

EMD_Driver · 07-12-2011, 07:25 PM

Thanks Gene.. I have the control/relay board, with a thermostat wired to it. It also has the wiring diagram on it. I sure hope he didn't smoke the compressor!

Drake · 11-21-2011, 09:08 PM

EMD Driver,
I was reading through some old posts and wondered what you found out on the situation above...did he smoke it?

**JohnB** · 11-22-2011, 11:08 AM

Hi Gary

Some how I missed this post when it came out a while ago.

I'm making a wild assumption this might be the AC unit from the T299?

To answer the question: Can you hot wire the AC unit without the control module or the t start? That answer is yes you can and I have done it trouble shooting a frozen fan motor from condenstation. The control module is pretty simple in these things. It is basically a relay setup that the T stat truns on the relay and the relay contact acts as the switch to turn on the fan and compressor as needed. Both fan and compressor have their own relay if I remember right.

Now as to the wire colors, I have no idea which hot wire trick he could have done. Done right it does work.

Gene's wiring diagram looks different then I remember on mine. The roof unit looks about right but the control unit does look a little different. His being a smaller TT may not have ducted air. Mine and your T299 had ducted air. The control module may be slightly different, not that that really may matter much in this case. There should be a furnace tie in on that module so you cannot start the AC with the furance on. I know mine has it.

If this is the T2999 unit, it may have had issues during the crash. The shock to the compressor being on it's side may have taken it's toll.

Here is my control module. On mine the large power comes out as Blue off the relay. I have to find the total wiring diagram to be sure as colors can some time change going across the plug.... These where the only pics I had up on the server right now. more at home.

Old one next to a new one. It wasn't the control module... so now I have a spare.

Here are the start capacitors

John

EMD_Driver · 11-22-2011, 07:34 PM

Quote:

Originally Posted by Drake

EMD Driver,
I was reading through some old posts and wondered what you found out on the situation above...did he smoke it?

Sorry for not following up on this thread.. He did not smoke the compressor. It was bad from the factory.

Quote:

Originally Posted by JohnB

Hi Gary

Some how I missed this post when it came out a while ago.

I'm making a wild assumption this might be the AC unit from the T299?

To answer the question: Can you hot wire the AC unit without the control module or the t start? That answer is yes you can and I have done it trouble shooting a frozen fan motor from condensation. The control module is pretty simple in these things. It is basically a relay setup that the T stat turns on the relay and the relay contact acts as the switch to turn on the fan and compressor as needed. Both fan and compressor have their own relay if I remember right.

Now as to the wire colors, I have no idea which hot wire trick he could have done. Done right it does work.

Gene's wiring diagram looks different then I remember on mine. The roof unit looks about right but the control unit does look a little different. His being a smaller TT may not have ducted air. Mine and your T299 had ducted air. The control module may be slightly different, not that that really may matter much in this case. There should be a furnace tie in on that module so you cannot start the AC with the furnace on. I know mine has it.

If this is the T2999 unit, it may have had issues during the crash. The shock to the compressor being on it's side may have taken it's toll.

Here is my control module. On mine the large power comes out as Blue off the relay. I have to find the total wiring diagram to be sure as colors can some time change going across the plug.... These where the only pics I had up on the server right now. more at home.

Old one next to a new one. It wasn't the control module... so now I have a spare.

Here are the start capacitors

John

Hi John,

The A/C I was working with, was given to me by a friend. I had hoped it would work, but the compressor was bad from the factory.

I still have hopes of installing the 299's A/C on the 311...

The guy that gave me the bad A/C also gave me a brand new shroud, to go with it... Free.....

**JohnB** · 11-22-2011, 08:04 PM

Quote:

Originally Posted by EMD_Driver

I still have hopes of installing the 299's A/C on the 311...

The guy that gave me the bad A/C also gave me a brand new shroud, to go with it... Free.....

A brand new shroud for free? You lucky duck! It's amazing what they what for those things. When I bought my last one I up'ed the bucks and went for life time warranty. My Dometic had truned into crack city. The lack of love from 303 UV protectant when it was new...

A double AC on the 311? Now that would be "cool"

I couldn't resist.

John

EMD_Driver · 11-22-2011, 08:22 PM

Quote:

Originally Posted by JohnB

A brand new shroud for free? You lucky duck! It's amazing what they what for those things.

I almost fell over, when he said "You can have it..."

Quote:

Originally Posted by JohnB

My Dometic had truned into crack city. The lack of love from 303 UV protectant when it was new...

The shroud on the 299's A/C isn't in the best shape. The shroud on the 311's is in surprisingly good shape!

Quote:

Originally Posted by JohnB

A double AC on the 311? Now that would be "cool"

I couldn't resist.

John

I certainly hope so!!!

I'm still undecided, about the best way to wire it. Since our generator is only capable of producing 3,600 watts, It almost seems foolish to upgrade the whole coach to 50AMP. I could tear a page out of your book and simply run a 12g cord to the pedestal, for the second A/C. My only reason for wanting to put the second A/C on, is because the existing one cannot keep up when it's very hot and "Sunny" (Pun intended)

If you would be up to the task, I wouldn't mind bringing the unit to Buttonwood and getting a bit of help with the install... (Hint Hint!)

**JohnB** · 11-22-2011, 09:08 PM

Well I suppose we carried it "off" the roof, why not put it back up there?

Yes even ours in the hot summer gets a work out. I find if we time it just right and still have the window shrink plastic left on from winter camping it helps with the heat entry.

John

Drake · 11-29-2011, 11:37 AM

When I bought my ' 88 Seville, the the shroud was as brittle as a cracker. It also had a big hole in the middle of the top and several of the side vents were broken. I was like you guys...STUNNED at the cost of a new one. So I wrapped up the A/C unit in plastic after carefully removed the shroud to see if I could possibly salvage it. I found that about $30 worth of fiberglass cloth and resin from the auto shop did a great job in restoring the old shroud. I put some screen over the hole in the top...resined that in, them put some fiberglass cloth over the screen and resined that on as well. I went over the whole shroud top with resin and used resin and cloth on any cracks. When the whole shebang had dried and I sanded out the rough spots and repainted it, it didn't look new, but it was as strong or stronger than a new one. I recommend this process to anyone who can't shell out the big bucks for a new shroud and doesn't mind taking off a year or so of his life by inhaling resin fumes.... seriously...do this outdoors and wear a mask!!!!