Which Dometic soft start do I need for Penguin II AC? DMC52RR vs DMC77RR
Updated 04/23/2026 | Published 04/19/2026
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Question:
I have a Dometic Rv air conditioner model 970003821 one that has a duct system and thermostat and the other controlled on the sealing . and I am wanting to add a smart starts do I buy?
asked by: Pete F
Expert Reply:
Hi Pete, based on the model number 970003821, you most likely have Dometic Penguin II style rooftop air conditioners.
The correct soft start depends on how each of your air conditioners is controlled. If one of the units uses a wall thermostat and duct system, that is considered an electronic setup and you would want the Dometic Soft Start part # DMC77RR. If the unit has controls right on the ceiling assembly with knobs or buttons, that is a mechanical setup and you would use part part # DMC52RR instead.
To make sure you get the right one and avoid any headaches, the easiest way to confirm is to look at each AC unit individually. If you see a wall thermostat controlling that unit, it needs the electronic version. If the controls are built into the ceiling vent itself, it needs the mechanical version. Since you mentioned you have one of each style, it’s very likely you would actually need one DMC77RR for the ducted thermostat-controlled unit and one DMC52RR for the ceiling-controlled unit.
Both of these are designed specifically for Dometic Penguin II systems and reduce startup power by up to about 75 percent, which helps prevent breaker trips and makes it much easier to run your AC on limited power or a generator.
If you can, take a quick look at each unit and confirm which style you have on each one, and I can double check it with you so you know you’re getting exactly the right parts the first time. Which one are you planning to upgrade first, the ducted one or the ceiling-controlled one?
Product Page this Question was Asked From
Dometic Soft Start for Penguin II Mechanical Air Conditioner Setup - Single Zone - Qty 1
- RV AC Soft Start
- 20 Amp
- Plug-In
- No Surge Protection
- Single AC
- Dometic
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