Date: Thu, 17 Jul 2008 09:33:46 -0700
Reply-To: Michael Diehr <md03@XOCHI.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Michael Diehr <md03@XOCHI.COM>
Subject: Re: Dometic won't light troubleshooting
In-Reply-To: <20080716173816.UOJI18077.eastrmmtao105.cox.net@eastrmimpo03.cox.net>
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Update --
A homemmade manometer revealed that my (5 year old) Marshall 290
regulator was only putting out 7 inches of pressure. I stretched the
spring and screwed the adjuster in full stop, which only took it about
9.5 inches. So probably my regulator is failing. With this
adjustment the flame looked a little stronger, but I still see
something glowing red. And, after running all night on LPG the temp
was only 60F. This same fridge on 120VAC will reach 33F over night,
and used to work reasonably well on LPG last year.
I'm skeptical that LPG pressure of 9.5 (instead of 11) would cause a
nearly complete failure of cooling. I'm thinking I better pull the
fridge again and bench test it to see what's going on. I'm getting
good at this fridge removal thing.
I've noticed that all the LPG connections have what appears to be a
coating of light machine-oil on them. Is this normal to have an oil-
like substance in the LPG tank and circulating through the feed tubes?
On Jul 16, 2008, at 10:37 AM, David Beierl wrote:
> At 12:55 PM 7/16/2008, Michael Diehr wrote:
>> However, left it running over night, and in the AM the temperature
>> was
>> about 60 (on 120VAC the temperature overnight was 33). Grr. :(
>
> :-( But it runs well on AC, so you know the cooling unit is ok. Has
> to be a matter of the flame. Gas pressure is first, since you can do
> that without taking the fridge out again. You want 11 inches of
> difference between the arms of a U-tube manometer filled with water
> for operation at sea level, one or two (?) inches less for way up in
> the big mountains (this is in lieu of the high-altitude orifice that
> Dometic doesn't supply any more). The manometer is simply a few feet
> of plastic tubing any convenient size, with the last three feet
> stapled onto a board in a tall thin U half filled with water and
> supported in vertical position to read. Press other end to regulator
> output to measure -- the gas pressure is only a few ounces per square
> inch. Approach the correct setting from below, and release the
> pressure any time you turn the regulator down. Try not to
> chain-smoke while doing this. <g>
>
> If that doesn't cure it, or spread the whole works over the
> landscape, you might think about getting a spare regulator and
> hooking it up to a BBQ tank with fittings to make up to the fridge
> directly so you can run it on the bench. Might be as much as $50 all
> told, which is about what I think uninstalling and reinstalling that
> thing once is worth -- not to mention the wear and tear on the
> bodyside flue fitting.
>
>
>> Taking a look at the flame, I see that it's blue, but with some red
>> glowing part as well.
>
> That might well be the piezo electrode in the wrong place, or it
> could be the thermocouple which of course has to stick into the
> flame. IIRC the thermocouple barely glows in the dark or not at all,
> so prolly not it unless the flame is too big.
>
> Next think I'd look at would be the orifice -- if you've run anything
> hard through it it's probably too big; if not I'd clean it per
> Dometic instruction with stove alcohol, grain alcohol from the liquor
> store (can't think of the name right now, but they'll know) or
> similar. I used to shove it through with a syringe IIRC.
>
> And this is a long shot, but there's some kind of turbulence
> generator in the boiler stack -- might be dimples pressed in the
> sides or might be something inserted inside, I forget. If the
> latter, and it's missing, the hot gases won't be hanging around as
> they should to do their work.
>
> It's possible to run the flame with the combustion box open, by the
> way. A nuisance, and you can't open it far, but enough to see the
> flame through.
>
> And if that fancy silicone gasket tears or whatever, high-temp RTV
> silicone gasket-maker works fine to supplement or replace it.
>
> IIRC the pilot flame hardly exists; the working flame about the size
> of a medium candle flame.
>
> Keep the faith!
>
> d
>
>
> --
> David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
> '84 Westy "Dutiful Passage," '85 GL "Poor Relation"
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