Going to update the AC unit with a Tosot

[ChristianD]

Tosot is having a sale, so I thought I'd pick one up and do the swap.  Just ordered it last night from tosotdirect.com, so it should get to me in about a week.  It's even cheaper on Amazon right now, but the seller doesn't have the best reviews so I went to the source instead.

Sale price is $1,059.99 with the soft start and around $960 without.  I went with the soft start option.

When I get it and do the install, I'll update this post.  Looking forward to this next upgrade!

Looking forward to the quieter than Dometic ac unit, and I think it will be nice to have the heater too. 

Ronbrink did a great write up on his install, so I'm going to comb over his post since I thought his install looked so clean.

 

[ChristianD]

I started the install, but have a question about the DC thermostat wire bundle loom, if anyone knows or has done this?

I'm assuming I cut these wires and wrap them since they won't be used for the new AC unit, but I wasn't sure if that would affect the Suburban furnace control from the thermostat? 

From reading the Atmos install from @Ronbrink, it looks like he had a Dometic furnace and a control box.  

 

I ordered the Tosot with the Turbro soft start and got that installed.  I followed this install video 

Here's the pictures from my wiring of the soft start:

After I figure out these thermostat wires, then I'll attempt to get the Dometic down and the Tosot up onto the RV.  I'm doing this solo, but think I have a method with a winch, some straps and using a beam from my garage barn to hoist them up and down.  Should be good, but will take some maneuvering.  

Planning a trip to Death Valley and Yosemite soon. Last weekend, we went up to Prescott, AZ for my our first trip together.  It was great!  

 

 

 

 

Edited October 26 by ChristianD

[ChristianD]

I asked ChatGPT.  Seems I will need a separate thermostat for the furnace now since I'm removing the Dometic control board.

------------------------------------

🧩 What You Have Now

That wiring harness under your Dometic Penguin II is the thermostat communication/control loom for your Dometic wall thermostat.

• It’s a 12 V DC control system (not 120 V).

• The loom carries low-voltage signals for both the A/C and the Suburban furnace (via the Dometic control board).

• The Dometic system acted as a “hub” — your thermostat told the A/C control box what to do, and that box sent the furnace signal out on the blue wire when “heat” was called for.

When you remove the Penguin II and its control box, you break that communication path. The Suburban furnace won’t get its 12 V heat-call signal anymore unless you rewire it to a simple independent thermostat.

---

🧰 What You Need To Do So the Furnace Still Works

Since your new Tosot A/C runs entirely off its own remote, you can leave those Dometic control wires disconnected and instead wire the furnace directly to a standard 12 V RV thermostat (or reuse your existing wall thermostat if it supports direct furnace control).

Option 1 – Add a small 12 V mechanical/electronic thermostat just for the furnace

1. Find the two furnace control wires coming from the Suburban unit (typically blue and white, sometimes blue/white stripe).

   • Those are the “thermostat loop.” When connected together, the furnace runs.

2. Route those two wires to a simple RV thermostat (like the Honeywell TH1100DV or Dometic single-stage heat only).

3. Connect them to the “R” and “W” (or “+” and “–”) terminals — polarity doesn’t matter on a basic furnace circuit.

4. Cap or tape off all the old Dometic A/C control wires safely; they’ll be unused.

Option 2 – Reuse the existing Dometic wall thermostat (only if it has a furnace setting and can directly switch 12 V)

If your Dometic wall stat is one of the basic analog models with a heat switch, you can bypass the old A/C control box:

• Connect the furnace’s two thermostat wires directly to the furnace terminals on that thermostat.

• Ignore all the data-bus or multi-wire cable that went to the A/C.

If your wall thermostat is digital and used an RJ-11 phone-type cable, it won’t work standalone — you’ll need a new simple furnace thermostat.

[katanapilot]

IIRC, the Dometic thermostat used originally for the Dometic Turbojet  Penguin A/C, had a digital communication protocol to the control box located in the Penguin.  This box had a couple of relays that were used to control the Suburban furnace.  There are a few posts somewhere on this forum on how I (and others) modified that box to continue to work with the Suburban.  Others have replaced the Dometic thermostat with a more conventional "analog" style to work when they removed the Penguin. 

[Treasure Coast Vault]

I eliminated the control box and used this Thermostat for the Heater.

Honeywell TH1100DV1000 Pro-Digital 2-Wire Heat Only

 

[Treasure Coast Vault]

I have a step by step on how I did my change out.

[ChristianD]

Thanks.  

From your write up, and for my to-do list, I need to:

Step 9 set the roof top unit in place. All the foam seal and leveling is attached don't overthink it just mount it. Hole is perfect size already.

Step 10 Open Dometic Furnace and use a continuity tester to ID the 2 wire from the Furnace. They were blue on the Furnace but changed to blue and green somewhere before arriving up at the interior hole on my Ollie

Step 11 Remove Dometic Thermostat and ID the wires to the Interior hole. I had a 3 wire Green, Red, White.

Step 12 wire 2 wires from Furnace to Red and white going to ThermoStat. Push the wires into the channel the wires are in up top to get them out of the way

Step... get heat only thermostat and place it somewhere.  

I saw ronbrink's post and write up and it looks like he grabbed the control box from the Dometic and was able to wire it that way.  At least that's what it looks like to me.  I removed the Dometic cover last night, but then my wife came out to the garage and wanted dinner, so I didn't get a chance to look at anything yet.  I'll get back up there later today and look for the control box.  My thought was that I'd sell the Dometic, so i'm not sure if I should remove that box.  I'll report back after I figure this out.  Thanks all for your help.

[Ronbrink]

6 hours ago, ChristianD said:

My thought was that I'd sell the Dometic, so i'm not sure if I should remove that box.  I'll report back after I figure this out.  Thanks all for your help.

Shortly after getting our 2020 OLEll I had trouble with the Dometic thermostat, one of the wire connector setscrews had been overtightened during assembly and the terminal block was cracked. Oliver sent a replacement, which was packaged along with another control box. I sold my Dometic with the original control box and installed the extra control box in the Atmos using the stock DC wiring harness. In my model year Oliver started installing the 11K Dometic Penguin ll, your’s is likely the 13.5K and may not have the same wiring/control setup. Regardless, the control box is readily available at etrailer.com and comes with a wiring harness which could easily adapt to your install. If you need more time to decide, cut the DC wires on the a/c side of the crimp connectors (for future reference), bundle them in the black wiring loom and complete your a/c install. You can then use the heat pump until determining how best to get the Suburban furnace back online. That’s exactly what I did! 

 

 

Edited October 26 by Ronbrink

[ChristianD]

7 hours ago, Ronbrink said:

I sold my Dometic with the original control box and installed the extra control box in the Atmos using the stock DC wiring harness. In my model year Oliver started installing the 11K Dometic Penguin ll, your’s is likely the 13.5K and may not have the same wiring/control setup. Regardless, the control box is readily available at etrailer.com and comes with a wiring harness which could easily adapt to your install. If you need more time to decide, cut the DC wires on the a/c side of the crimp connectors (for future reference), bundle them in the black wiring loom and complete your a/c install. You can then use the heat pump until determining how best to get the Suburban furnace back online. That’s exactly what I did!

 

Ron, you're using the Dometic thermostat controls only for your furnace?  I may wire up the furnace to a separate thermostat.  That seems like the easier route and cheaper too.

I ended up getting the old Dometic down and the new Tosot mounted.  It took some finagling and a trip to Harbor Freight for a snatch block. The pictures show the old coming off and the new going up.  I pulled the Oliver up once I got the old unit up and then lowered down the AC.  Then I pulled the new unit up and backed the trailer under it before lowering it back down.

Glad that's over.  I hooked the power up, but need to get my generator out in order to test it.  I don't have electrical / power yet in the garage.

[Ronbrink]

8 hours ago, ChristianD said:

Ron, you're using the Dometic thermostat controls only for your furnace?  I may wire up the furnace to a separate thermostat.  That seems like the easier route and cheaper too.

That is correct, only DC control wires to the furnace were used to operate it. I did not like the standard Suburban mechanical thermostat supplied with my Atmos from SDG. I tend to forego cheap and easy over a better option, but that’s just me. Nice garage, you got this!

Edited October 27 by Ronbrink

[ChristianD]

Slight update.  I'm waiting for a thermostat, but I also found the Dometic control box that Ron posted a bit cheaper on 
https://thervsurplus.com/search?q=Dometic™+OEM+3316230.700+(9600024570)&options[prefix]=last so I ordered one. 

We're going on a weekend trip and I don't think I'll have either of them hooked up, so maybe next week.

Buttoned up the AC unit for now.  Works great and it's quiet. 
I tried to power it with my Honda EU2000 generator, but it didn't turn on.  Thought it might, but no bueno.

Edited October 28 by ChristianD

[jd1923]

2 hours ago, ChristianD said:

Buttoned up the AC unit for now.  Works great and it's quiet. 
I tried to power it with my Honda EU2000 generator, but it didn't turn on.  Thought it might, but no bueno.

Next, we'll have to get you into a Victron Multiplus II with PowerAssist! I've used ours a couple of times when on 15A shore power connections. From Victron:

PowerAssist – Extended use of generator or shore current: the inverter/charger “co-supply” feature, allowing the inverter/charger to supplement the capacity of the alternative source. Where peak power is often required only for a limited period, the inverter/charger will make sure that insufficient AC mains or generator power is immediately compensated for by power from the battery. When the load reduces, the spare power is used to recharge the battery.

[ChristianD]

1 hour ago, jd1923 said:

Next, we'll have to get you into a Victron Multiplus II with PowerAssist! I've used ours a couple of times when on 15A shore power connections. From Victron:

I started looking into the Victron stuff, but that's on the back burner for now.  If you saw a picture of my garage, you'll notice I don't have garage doors, electrical, or the built out workout area that I told my wife about 🙂   

Yesterday, we had a crew out here working on the outdoor cement aprons.  Got the dug out and framed. Next is the concrete pour.  Garage doors are getting installed in a few weeks and I'll probably put a EG4 inverter and a 48v battery in with a few solar panels for now.

[jd1923]

9 hours ago, ChristianD said:

If you saw a picture of my garage, you'll notice I don't have garage doors, electrical, or the built out workout area...

Wish we had that much flat ground, let alone a garage large enough for the Oliver and much more! First thing I would do is trench some power to that garage, install a sub-panel, add a 30A outlet and a few lights and regular outlets to start.

Our home has 200A service and I've run cable and added 4 sub-panels for many needs. The last one was to our TuffShed next to where we park the Oliver, with a 30A outlet there.

Electrical work is the easiest upgrade, though everything costs $$$. Do the doors later. It's not like it's going to snow down there! 🤣

Edited October 29 by jd1923

[ChristianD]

We're on about 1.25 acres.  When we moved to AZ, about 5 years ago, my wife wanted a house that was move in ready, had a pool and I wanted a large garage.

We bought a house that was move in ready and that was it.  No pool and a 2 car garage with very little extra room for "stuff".  We had a pool built about 2 summers ago as our first major project.  Took over 2 years to get it done with permitting and contractor issues. 😞  I steadily cleared the back of the lot and a pathway to the back.  Before I started doing that, you could barely walk to the backyard, it was so overgrown and unkept. 

Next project is/was the garage.  Just got the garage barn up a few weeks ago.  I grew up with uncles that had barns, so it's been a dream most of my life to have one.  I'll enjoy the build out, since I like doing those kind of projects.  I have a few generators for now to power the building and plan to add solar.  I may trench a line for power and water, but want to get some other stuff done first.  I've remodeled a few houses and can do basic electrical but haven't done anything like a subpanel or full electrical wiring yet.  I don't think it's beyond me, but I'll have to go to Youtube and ChatGPT school for a lot of it.

Like you said, everything cost $$$, time is limited too and I'm not as young as I used to be.

[jd1923]

3 hours ago, ChristianD said:

I grew up with uncles that had barns, so it's been a dream most of my life to have one.

Our last home in Chicagoland was a dilapidated 1943 farm house, but we had a 40x60' pole barn on 3.2 acres (50 miles NW of downtown). I poured concrete on half of it, ran power, was able to work on cars in the winter with a bullet heater, was in heaven!

We have 3/4 acre here within Prescott city limits. Bought our home with a GREAT deep 3-car garage, an outbuilding just smaller than a 2-car garage and I added a 10x20' TuffShed. Carports are not allowed by the city anymore and our Oliver must be outdoors. I do have an idea to mount some metal panels top of the TuffShed to provide more shade, but worried the city would frown on this idea!  

[SeaDawg]

7 hours ago, ChristianD said:

I steadily cleared the back of the lot and a pathway to the back.  Before I started doing that, you could barely walk to the backyard, it was so overgrown and unkept. 

Next project is/was the garage.  Just got the garage barn up a few weeks ago.  I grew up with uncles that had barns, so it's been a dream most of my life to have one.  I'll enjoy the build out, since I like doing those kind of projects

We'll look forward to the finished photos. Then again, many of us with small lts  will have a pang of jealousy....

Best of luck!

[Ronbrink]

On 10/28/2025 at 8:32 AM, ChristianD said:

I tried to power it with my Honda EU2000 generator, but it didn't turn on.  Thought it might, but no bueno.

There have been a couple of occasions when trying to run on my smaller generator or 15A service that the inverter’s charger would also kick on and the a/c would shutdown shortly thereafter due to a power exceedance. You may try reducing the charger output or turning the inverter/charger off completely. Your EU2000 should run the TOSOT with a soft start if there are no other power demands. You could also charge the batts to 100% SOC with the EU before attempting to operate the a/c. Food for thought!

Edited Friday at 07:17 PM by Ronbrink

[ChristianD]

I found the issue with the generators now working.  My Honda generators have a "floating neutral" and the Tosot won't power on without the neutral grounded.  I made a plug that jumps the neutral (silver side) to ground and plugged in the regular plug, plugged into the rv, fired up the generator and the AC powered on!  Both my Honda EU2000 and 3000 work with it like that.

Solution:

Ground / Bonding Plug

Some RV A/C units + soft starts will NOT start from an unbonded generator (floating neutral).
They see it as a fault and won't engage the compressor.

Honda portables = floating neutral

Fix: Use a neutral-ground bonding plug in a spare outlet on the generator.

Example DIY bond plug:

• Standard 3-prong plug

• Jumper neutral to ground inside

[Ronbrink]

32 minutes ago, ChristianD said:

Some RV A/C units + soft starts will NOT start from an unbonded generator (floating neutral).

This is a thing all Oliver owners using generators deal with, no supplied AC for anything without one!