Date: Mon, 17 Aug 1998 09:15:32 -0700
Reply-To: Bill Davidson <davidson@SIERRA.NET>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: Bill Davidson <davidson@SIERRA.NET>
Subject: Off list Dometic Solutions:
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I just joined in on 'the list' in the past two weeks or so and didn't
realize that 'Reply to Author' messages do not show up on 'the list'. Since
the "Pesky Dometic" is such a big issue, I am including below my 'Reply to
Author' responses thinking that perhaps others on 'the list' may find them
heplful:
sent 8-10:
Re: Fridge:
I know it sounds like a contradiction but trust me, what makes the fridge
work is heat applied to a particular part of the tubing on the back. (I
will not attempt to explain the physics, and it is not necessary to know.)
If you were to take out the fridge and look at all the tubes, etc. on the
back of the Fridge you would see that the heat, weather created by 110V,
12v, or gas is applied at the same spot in the tubing. So, assuming that
your propane does indeed light and stay lit, the refridge should work
pretty much the same weather you are using 110v or gas. However, if the
refridge was empty when you got it going the night before you left for your
trip and then you packed it with food, the problem may be that the food is
packed in so tight that it restricts air flow. Check to see if the fins in
the upper part of the fridge get cold on gas and 12v (give it at least 1/2
hour). If the fins get cold, the fridge is working. In order for the fins
to cool the food in the fridge there must be air movement over the cold
fins and down into the bottom of the fridge. When you pack the fridge you
must leave a space for the air to circulate. In addition, and this is
extremely important, go to an RV place that sells gadgets and buy a small
battery operated fridge fan. That will blow air up over the cold fins and
through the space you left for airflow down to the food at the bottom of
the fridge. This really is necessary for the fridge to keep food cold!
Good Luck! .... Bill
sent 8-11:
Marty:
We need more information:
Here are some things to check out:
1. Make sure you try the fridge on gas and 12v under the same conditions as
the 110v/
(ie: level in your garage, close to same outside air temp, etc)
2. Check the two fuses behind the driver's seat.
3. Make sure the gas burner stays lit: (put your ear to the exhaust vent
outside the van)
4. Check the connections at the relay in the aux battery compartment under
the driver's seat.
5. Does the fridge indicator light come on both for 12v and gas operation?
6. Does the fan behind the fridge come on (check it on a hot day running on
gas)?
7. What was the outside air temp when you tried the gas when camping?
(these fridges only cool about 40-45 degrees below outside air temp...
from the mid 90's on up your fridge won't be very cold inside!...
outside air temp means at the foot of the fridge where you find the
cooling air intake... if the van is closed up in the sun it will be a lot
hotter inside the van than outside!)
8. Unless you have an aux battery or have by-passed the relay under the
driver's seat (not recommended as this will allow the fridge to drain
your starter battery), 12v will only work with the engine running,
and the fins inside the fride won't begin to get cold for 1/2 to 1 hour.
Bill Davidson 90' Westy Syncro
sent 8-11:
George:
If nothing has changed mechanically on your fridge since it was not blowing
out and you have not changed altitude, I suggest checking the gas pressure.
It should be set at 11 inches w.c. You either need a manometer to check it
yourself or have a RV shop check it for you. Let me know if you have
success because I have the same problem, but in my case I know that I have
turned the pressure down so that the fridge will start on gas at altitude!
Good Luck: Bill Davidson
sent 8-11:
Darrell:
After running your fridge all night so drastically out of level (front 2ft
higher), does the fridge still work on 12v and 110v?? If the fridge works
on both 12v and 110v it should work be working on gas if the flame stays
lit.
If you don't know already, you should know that running the fridge far out
of level like that can ruin the fridge such that it will not work in any
mode (12v, 110v, or gas)! If you can't park the van close to level it is
better to turn it off than to ruin the fridge.
Good Luck: Bill Davidson
sent 8-11:
Dometic fridge does work at altitude, but you may have to turn down the gas
pressure to compensate for less oxygen to burn at altutude, especially if
the weather is cold. Dometic claims that at altitudes like 8,000ft you may
have to turn the gas prussure down as low as 5 inches w.c. I live at 6,0000
ft and have found that 10 inches w.c. works fine here and up to about 8,000
ft as long as it is not too cold.
Bill Davidson
sent 8-11:
Frank:
The basics of the Dometic are simple, however the circumstances of optimum
cooling can be complex. Since the heat is applied in the same spot to make
the fridge work, if all three systems are supplying heat, then, assuming
all other circumstances are the same, all three modes (12v, 110v, and gas)
should cool the fridge. After you have confirmed that all three modes do
indeed supply heat without interruption to the back of the fridge, it is
important that you test all three modes under as close to the exact same
circumstances as is possible. That means level of the vehicle, outside air
temp, length of cooling test, how the food is packed in the fridge (leaving
room for air circulation), fridge fan, etc, etc.
I suppose it is possible that you have an intermittent thermostat problem
or something odd like that, but I suggest that you check out the more
mundane items above first.
Good Luck: Bill Davidson
sent 8-11:
If the air temp behind the Dometic fridge is warm enough, the fan comes on
regardless of 12v, 110v, or gas mode. In fact, the fan will come on even if
the fridge is turned off! That's because it is controlled by an independent
air temp switch.
Bill Davidson
sent 8-11:
Larry:
I have heard this advice before regarding equal length exhaust and air
intake pipes. However, there are two problems with the advice:
1. How do I measure such irregular pipes. I heard that the measurement must
be exact, but just you try to measure the pipes! The pipes twist and turn,
and the exhaust pipe, for instance, connects to the more rigid pipe that
leads to the burn chamber. But this more rigid pipe is wrapped in
insulation to facilitate the heat transfer from the exhaust pipe to the
cooling tube system. In short, very irregular and difficult to measure at
all, not to mention measuring exactly!
2. Where does one measure from? For instance, both pipes fit into a
manifold that fits into the wall of the van. Do we measure just the pipes?
Or do we include the part of the air pathway that is created by this
manifold? Also, where does the burn chamber come into play? Do we measure
from the flame or just to where the two pipes enter the burn chamber?
The advice is simple, but the measurements are more complex. I attempted to
cut the pipes such that the entire air pathway, including the van wall
manifold, was equal for the exhaust and the intake. But my flame still
blows out at about 40 mph! Do you have sage advice on the proper measuring
technique??
Thanks... Bill
sent 8-15:
Hi Roy!
I have played around a lot with my dometic. Especially the fan and heat
activated fan switch. The hair dryer should be enough to make the switch
come on if you can get it close enough. All it needs is to get up to 126
degrees F and it should come on. You could also try one of those long
lighters or long match stick that is used for lighting fireplace fires &
BBQ grills. I don't think I would use hot water since it is an electrical
component. When it switches on you should hear a distinctive pop sound
(unless the hair dryer is too loud). But if you're going to take the fridge
out of the cabinet anyway you could just connect the fan wires to a 12v
source with alligator clips to see if it works or not.
I don't have much data to support this but I think the fans are known to go
out more frequently than the switch. In any case, you should be able to buy
either or both the fan and the switch at any Dometic authorized service
center. There is a really good on in Sacramento, CA that will even mail
order the parts to you: AAA Appliance: 916-920-1032 -- for parts ask for
the parts counter. They also have a guy that is really great with these
Dometics. His name is Rick and he's been working on Domeitcs for many
years. I made an appointment ahead with him and he had me in and out in 2
hours. In my case the fan was burnt out and the thermocouple needed
replaced (flame not staying lit). I suggest if you are going to work on
these yourself go down to Radio Shack and get yourself a volt meter that
can test for continuity, amps, etc., It really helps.
I went through all this last spring and after Rick got the fan working I
heard how loud it was for the first time and decided it would be an
annoyance out in the quiet of the desert canyons. So I replaced the one
stock fan with 3 strategically placed Fridgemate fans. They are much
quieter and after testing them with my amp meter I found that three of them
used about the same amps as the one stock fan that comes on the Dometic.
And though no single one of them is as powerful as the stock fan, I think
the fact that they are better located along the path of air circulation
makes for better over all ventilation and therefore cooling.
It does concern me that you had to turn the fridge upside down to get it to
work. Was it working on 12v and 110v before you turned it upside down?? If
not, I would be wondering if you have a restriction someplace inside the
cooling tubes. That would explain it cooling again for awhile after turning
upside down. It is my very limited understanding understanding that these
fridge tubes eventually clog up, especially if you run the fridge out of
level. And I don't think these clogs can be repaired. It would be get a new
fridge time I think. But if it was working fine on 12v and 110v, perhaps
the problem is indeed the fan. The propane uses more heat to get the fridge
going so the fan would be even more important to the fridge getting cold on
propane than on 12v or 110v.
Good Luck Roy! These Dometics can be pesky. We may need all of our brains
and experience to keep them running! So let us know what you find out so we
can add it to the data file!
Bill davidson@sierra.net
sent 8-15:
Hi again Roy!
You can pull 12v off your battery under the passenger seat. You can also go
to most any auto store like Grand Auto or Kragen or even Radio Shack to buy
the male cigarette lighter accessory plug with two wire ends on it. Then
attach alligator clips (the ones with shields are better: less likely to
short out on each other) between these two wires and the fan to see if it
will go.
The 3 fans that I used are Fridgemate Model A10-2710 Coil Fans. They are
sold in RV places like Camping World to improve fridge performance. Camping
World has a web site that you can mail order from. I added one of these
fans pretty close to where the original fan was mounted. The second I
mounted about half way up the back of the fridge just beneath the upper set
of cooling fins. The third I mounted on top of the fridge directly in front
of the side air vent by the table. (I also felt the side vent too small so
I enlarged it and used 3/4 or 1/2 inch flat expanded metal for a new grill.
Even without the third fan this lets a lot more hot air out from behind the
fridge than the original set up. With the third fan directly in front of
the larger fan and new grill, the hot air really blows out fast!). All
three fans together use about the same amps as the one original fan. And
since they are spread out more or less evenly along the air pathway, I feel
that they keep the air moving better than a the single original fan. All
three fans are wired to the original air temp switch! This was quite a bit
of work, but I am a nut about noise out when I'm camping and I believe the
fridge cools better now in warm weather. There are a few subtle details
about reworking/fitting the fans. If you are interested let me know and I
will take the time to remember and write the details out as best I can....
Good Luck Roy! And let me know how it goes... Bill davidson@sierra.net
sent 8-16:
Frank: I have to say it sure sounds strange when a Dometic works fine on
12v & 110v and not on propane (assuming propane lights and stays lit)!
Really the only problem I've had with it working on propane is starting it
and keeping it lit. It turned out that most of that problem was from an
intermittently failing thermocouple AND the fact that I live at 6000 ft.
The solution was to replace the thermocouple and turn the gas pressure down
so that the amount of gas in the burn chamber was more balanced to the less
oxygen available at higher altitudes. But I did tinker with my fridge quite
a bit last spring and have done a lot of thinking and trying to understand
this fickle creature. I always take an interest in knowing more about the
Dometics, probably because I have this intuition that eventually another
problem will surface and I will need the information to keep the thing
going. Anyway, the following are my thoughts (in no particular order) on
possible reasons why a fridge would work/cool on 12v and 110v and not on
propane:
1. Air intake or exhaust pipes restricted or clogged (spider webs, dust,
etc)... blow or brush them out. (possible but would expect there would be
problems starting or keeping flame lit).
2. Flame not staying lit.
3. A crazy thermostat that only works on 12v and 110v??? (I don't believe
this is possible, but who knows??)
4. The fan behind the fridge is burnt out. (a burnt out fan would inhibit
cooling more in the propane mode than 12v or 110v since the propane mode
creates more heat behind the fridge).
5. A restriction in the cooling pipes on the back of the fridge that for
some reason is more likely to clog up on propane than 12v or 110v (propane
does create more heat than the 12v or the 110v so perhaps this more heat
somehow affects the chemicals in the pipes differently?).
6. Some combination of 4 and 5 above along with the van being out of level.
(a fridge on propane, creating more heat that a burnt out fan does not
dissipate, along with a previously existing restriction in the pipes, might
be even more susceptible to clogging when out of level.)
7. Perhaps 12v & 110v modes are being tested under different conditions
(air temp, level, warm food just put in fridge, food stuffed in fridge
restricting air circulation from cooling fins to food, etc.)
8. Gremlins in your propane tank??
I would suggest checking out items 1,2,4,6,&7 yourself. If one or more of
those is not the solution I would suggest finding a VERY good Dometic
service person who has lots of experience with these particular models. If
you are in or are coming to Northern California I can recommend Rick at AAA
Appliance... 916-929-9777.
Regarding out of level operation of Domeitc: As I understand it, if you
operate the fridge too far out of level too often a certain chemical comes
out of solution and forms crystals that clog the cooling tubes on the back
of the fridge. I think this is a fairly slow process that takes place over
the years like clogging of the arteries. So you could have gotten away with
it running the fridge out of level many times before seeing the effects and
at a certain point the effects could be intermittent. Some people suggest
taking the fridge out and turning it upside down to clear the clogs. I
would think that this would only be a temporary solution. Good Luck... Bill
davidson@sierra.net
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