1991 12 volt fridge info

[Planck]

Just joined the forum after 7 years of owning a 91 190. I now have a 93 190, but would like to share a little info on the 12 volt fridge mode on my 91. When acquired I had problems in the 12 volt mode and found that no 12 volt power was getting to the fridge. I traced the problem to under the bed where the circuit panel is. There was a relay there that had been altered that was tied in to the 12 volt fridge. I called Airstream and they did not know what the relay was for. I bypassed it and the fridge worked ever after with no problem. However, I now think the relay was to cut out 12 volt power to the fridge either while the ignition was on, or while it was off. The high current draw could possibly damage the alternator if used while driving, or could possibly run down the house battery quickly when not driving. I don't know which it did. I also called the fridge manufacture and they said that the 12 volt is only a maintenance mode, and will not cool down a warm fridge. They also shared that the 3 mode fridge is no longer made and that LP was to be used while driving. Note that the Airstream manual says that all gas appliances should be off when refuling.

Just thought I would share this for anyone who has the first generation 190

Phil

[skater]

Interesting. My fridge actually has 12 volt power when the ignition is on, and not while it is off. My understanding is that this is because the alt can produce enough power for the fridge while it's running (10 amps, if you're curious), but it'll quickly kill a battery if the engine is off.

The odd part is why that would need a relay - it could easily just be wired to the accessory power of the ignition. Mine has no such relay that I'm aware of, and I replaced the circuit panel and all.

[Planck]

Okay, you answered one part, that the fridge kicks in in 12 volt when igition is on. The relay on mine was to the left of the power panel, sort of down on the floor. My guess is because of the 10 amp draw, either Airstream or someone added the relay.

Since I hardwired the 12 volt fridge, it was always on. But, we usually(98%) stayed at campgrounds with electric hookup, so never had a problem with the house battery.

[skater]

Okay, you answered one part, that the fridge kicks in in 12 volt when igition is on. The relay on mine was to the left of the power panel, sort of down on the floor. My guess is because of the 10 amp draw, either Airstream or someone added the relay.

Since I hardwired the 12 volt fridge, it was always on. But, we usually(98%) stayed at campgrounds with electric hookup, so never had a problem with the house battery.

The more I think about it, it makes sense that it could be done through a relay - run a heavy gauge wire from a power source, then use a relay to trigger it (this is how amplifiers in cars are essentially wired, for example, and I use a relay to cut power to my Sirius tuner in the camper). I guess it depends on whether there is a spot to connect something that's going to draw 10 amps from the engine's electrical system. But there are plenty of 15 and 20 amp fuses in the fuse panel so you'd think that wouldn't be an issue...

[bobbyv]

Hey there skater and planck, have been reading your comments about the fridge and am just wondering. When the fridge is in 12v mode, just exactly what is going on. What is actually happening in the 'maintenence mode'? Is there some kind of a sepeate refrigeration unit built in the fridge? I'm not fully understanding how the fridge stays cold in 12v. Can anybody shed some light on this. Thanks

[skater]

Hey there skater and planck, have been reading your comments about the fridge and am just wondering. When the fridge is in 12v mode, just exactly what is going on. What is actually happening in the 'maintenence mode'? Is there some kind of a sepeate refrigeration unit built in the fridge? I'm not fully understanding how the fridge stays cold in 12v. Can anybody shed some light on this. Thanks

All three modes work by heat: they heat up the ammonia (or whatever liquid is in there), and as it cools it sucks in the heat from the fridge compartment. Check this out for a more detailed explanation of the physics behind it.

So, it's all about creating heat. Gas mode is obvious - it burns the propane to make heat. The two electric modes use a heating element, like an electric range or water heater uses. The 120 volt element can generate a lot more heat than the 12 volt element can, though.

So, the 12 volt mode basically works the same way as the 120 volt mode, just not as well. (I think the 12 volt mode uses a separate element, but I could be wrong - it may also use the 120 volt element.)

[Planck]

Don't think I can explain it any better than skater did.

[Roadhog]

There are two electrical elements. The main one is 120 volt AC, which I had to replace recently, and is used when connected to shore power (campground). A seperate 12 volt DC element is used for traveling. The 12 volt element is marginal in keeping the fridge cool. During the travel day if we stop to eat or tour, I usually switch over to gas and give the fridge a boost cool down before continuing on. This seems to hold the cooler temerature until we stop for the night and connect to 120 volt at a campground or switch to gas if dry camping. The 120 and 12 volt elements are stacked with the 12 volt above the 120volt.
Happy Travels, Howard

[bobbyv]

Thanks everyone for the great info. You all made it easier to understand, I just wish that the 12v element drew less amps. I used to own a Sportsmobile with a Norcold 12v/110v only, no gas. The 12v worked equally as well as the 120v and drew less than 5amps. Go figure! In the future I will get her cold on either 120v or gas and then switch to 12v while I'm cruising, that way at least on long trips I won't have to do anything when I stop at a gas station to fill up. Love this site and love my Airstream.

[skater]

I used to own a Sportsmobile with a Norcold 12v/110v only, no gas. The 12v worked equally as well as the 120v and drew less than 5amps. Go figure!

I wonder how that worked. Perhaps it was a compressor-based fridge (they're putting those in some RVs now), which would explain the lack of a gas mode.

[bobbyv]

not really sure skater, mine was a 95 and it instantly started getting super cold as soon as I turned it on. We could put ice cream in this thing within 20 min. and never worry about thawing. It was a great fridge, but I always wished I would have had the gas option especially after dry camping for a few days. Oh well I've adapted and I'm thankful for what I've got. Have a good day, bobby

[skater]

not really sure skater, mine was a 95 and it instantly started getting super cold as soon as I turned it on. We could put ice cream in this thing within 20 min. and never worry about thawing. It was a great fridge, but I always wished I would have had the gas option especially after dry camping for a few days. Oh well I've adapted and I'm thankful for what I've got. Have a good day, bobby

Yeah, that has to be a compressor-based fridge.

For those who may be unaware: compressor fridges are what you have in your house. They tend to cool down much faster and are much more resilient to hot weather and opening the door frequently. I think they're also able to deal with off-level situations better than an absorption fridge. The downside is they have a motor and thus require some form of electricity to operate, and they can make noise.

[bobbyv]

ok how about a 110/12v compressor fridge that could also run on gas? Wouldn't that be sweet, albeit probably too costly.

[skater]

ok how about a 110/12v compressor fridge that could also run on gas? Wouldn't that be sweet, albeit probably too costly.

How would the motor run? I suppose it could have a generator or something, but the complexity, noise, and expense would be pretty annoying.

[bobbyv]

hey I just thought about it, I'll leave it up to you brainiacs to figure it out.