Refrigerator not working correctly on DC

[Dagrip]

Hey folks,

This past weekend I discovered that the fridge in our 2007 2720SL was not cooling correctly when in DC mode. It does appear to be working when the TV is running (I need to test this further) but it is definitely NOT working when the TM is plugged in and the battery is charging. Everything appears to be working fine when the fridge is set to AC. I have not tested the propane mode.

I am going to dig into this tonight (taking the TM out on Thurs) so I wanted to see if anyone had any pointers on what I should be checking.

FYI...I spoke with the factory yesterday and was told that the fridge will only cool in DC mode when the TV is running. Based on what I have read on this board this appears to be false information.

As always...thanks a bunch for any information that you may have to share.

Scott

[Bill]

Scott -

If the refrig cools on DC when the tow vehicle is running, then the problem is not in the refrig.

It sounds like something is weird in the converter or the power distribution - but I can't imagine what.

As for the frig "not cooling on DC unless the tow vehicle is running", that is definitely not right. However, it sounds like a misunderstanding. When set to DC, the refrig draws a lot of current and can quickly exhaust the TM battery. The recommendation is that you not run the refrig on DC unless a) the tow vehicle is running, or b) the TM is connected to shore power. In those cases, the current drawn by the refrig will be replaced by either the tow vehicle's alternator or the converter.

The easy way to test whether the refrig is running? Switch it to DC, wait half an hour, then go outside and remove the vented panel over the top of the refrig. Put your hand inside the compartment, and feel for heat around the top of the vertical tube on the right. If there is heat, the refrig is running. If not, then it's not.

Having said that, I suppose it is possible that there was a change in the '07 models, to prevent the refrig from killing the TM battery. But I think this is highly unlikely.

Bill

[Speckul8r]

What they said but... I would remove the lower panel and cautiously put my hand near, then on the foiled covered insulation at the bottom right of the fridge. If that is hot, it should be working.

I routinely run my fridge on DC from shore power.

I usually prep the TM the weekend before a trip. This includes putting canned beverages of my choice in the fridge, setting the fridge on DC and the fridge fan to on and then closing the TM. The TM is stored in the garage and the battery is disconnected.

On Wednesday I plug the TM into shore power and connect the battery.

On Friday I pull the TM out of the garage and away we go. The fridge is still running on DC, but from the TV instead of shore power. When I arrive in camp the batteries are fully charged and the fridge is fully cold, and so is the contents of the fridge.

If the fridge was not running from Wednesday to Friday, I have no doubt that it would be warm when I arrived in camp. I don't think cooling while towing for 3 hours would be enough to cool down the fridge plus the contents.

The trouble with running the fridge on 12 v when plugged in to shore power is that it doesn't have a thermostat on 12 v.

[Dagrip]

So I just returned home and checked the fridge. The TM has been plugged in all day with the fridge set to DC. The temp inside the fridge is about equal to the temp inside the trailor so obviously the DC cooling is not operating. I pulled the exterior panel and also verified that the coil is not even warm.

Does anyone know if the DC power to the fridge is fused at some point? I mentioned earlier that the fridge does cool when the TV is running but really am not positive about this since the fridge was already cold (from AC power) when we left the campsite this past weekend.

Thanks again for the assistance!

Scott

[Dagrip]

Yes...I did a quick check of all connections and they appeared to be intact. I just finished going through the wiring diagrams and it appears that there should be a 3A fuse inline so my next quest is to find this fuse. It's getting dark so I will dig into this further tomorrow.

Thanks again!

Scott

Another note: From my experience, don't use the 12v intransit if you are going to dry camp.....it still depletes the battery some, even with the TV charging the system and running the fridge.

Chap

[Bill]

Scott -

My TM Blue Book - the bible - is in my TM, which is closed up across town, so I am working from memory. Bear with me.

First. Yes, the refrig has an internal power fuse for the DC power. You mentioned finding a 3-amp fuse, but that's too small for the DC power fuse. This one is probably the AC power fuse. In the DC line, the fuse should be something on the order of 20 amps. Without my book, I don't know where to tell you to look for it - but it is there.

Second. Jim/Freedom mentions that there is no thermostat control of temperature when running on DC, and this is true for the refrigerators that TM has been using since about 2005(?) Just for the record, I don't think that was true for earlier refrigerators (Dometic/Suburban?), so owners of earlier TMs can take heart.

Third, mtnguy mentioned that it may not be wise to run your refrig on DC while in transit, if you won't have hookups at the end of the day, and in many cases this is also true. The wiring in many (but not all) tow vehicles is too light to support the high current demand of the refrigerstor, and the TM battery is depleted. I finally had to run a new charge wire and ground wire down the length of my Explorer to remedy the problem.

Finally, you wrote

So I just returned home and checked the fridge. The TM has been plugged in all day with the fridge set to DC.

Plugged into what? I'm still a bit confused about when DC-power works and when it doesn't. When the TM is plugged into shore power? When it is plugged in the tow vehicle? When the tow vehicle engine is running?

At the moment, my guess is that the refrigerator's internal 12-volt fuse has let go.

Bill

[commodor47]

Bill,

Here is a copy of the wiring diagram for our unit.

http://picasaweb.google.com/commodor...orInlineFuses#

If I am reading the diagram correctly, there is a 20 A circuit breaker for the AC leg of the refrigerator and a 15 A (blade type) fuse for the DC leg.