Home » Public Forums » GMCnet » [GMCnet] Roof AC Rattles on startup
| [GMCnet] Roof AC Rattles on startup [message #144463] |
Sun, 25 September 2011 08:31  |
Erv Troyer
Messages: 125
Registered: February 2004
Location: Lagrange, IN
Karma: 0
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Senior Member |
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On Sat, 24 September 2011 18:08 D C "Mac" Macdonald wrote: <in part>
>>>>>>>>>>>>>>>>
Figured I'd turn on the on-board air system just for grins. Great
clattering and rattling occurs,
but what the heck! Maybe it will just die and be done with it.
<<<<<<<<<<<<<<<<<<
Mac, about that "clattering and rattling" -
This is for all of you with the original Duo-Therm roof air conditioner
(and there are quite a few, judging from the coaches at Goshen at GMCMI). You
can tell if you have an original Duo-Therm AC if you have a third control
knob that controls the air flow to the front or the rear of the coach.
These units use a piston type compressor which vibrates somewhat on the
first startup, but they are mounted on rubber grommets so the noise in the
coach should not be very loud, and should quiet down to a gentle "purr"
within a few seconds. However, if you hear a very loud metal-to-metal hammering
when the compressor first starts, then you probably have a mis-installed
mounting bolt.
The compressor is mounted directly above the mounting bolt hole located at
the passenger side rear of the unit. We (Duo-Therm) provided a special
mounting bolt that had a 1/2 inch thread at one end and several inches of
thread at the other end. The installer was supposed to install the short end
into the air conditioner, and if the bolt was too long for the roof thickness
they were supposed to cut off the long threaded end to fit. However, I
have seen many of these where the installer was too lazy to cut off the bolt
so they put the long threaded end up, put a nut on the short thread, and
cranked up the bolt. This forces the bolt against the bottom of the compressor
- and you get a severe noise when the compressor starts.
To check this bolt you have to remove the complete air box from the
ceiling. If you find this bolt with the short thread at the bottom, then you will
have this problem. Remove the bolt, cut it to the right length, then
re-install it with the short thread turned up.
I would have thought that after 30 years these problems would have been
corrected, but I guess there were some owners that just thought that was how
they were supposed to work - I found a 1977 Birchhaven in 2010 that STILL
had this problem. This was a Coachmen built unit, and it reflects the
typical poor workmanship that I have seen so many times in northern Indiana built
RV's in the 70's and 80's. I am not trying to get an argument started with
that statement - but I calls 'em as I sees 'em.
Erv Troyer
Lagrange, IN
(26 years with Duo-Therm)
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Erv Troyer Lagrange, IN
74 Sequoia
reo43@aol.com
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| Re: [GMCnet] Roof AC Rattles on startup [message #144465 is a reply to message #144463] |
Sun, 25 September 2011 08:48  |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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Senior Member |
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The "clattering and rattling" was from the
air suspension system's compressor, NOT the A/C.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
~ ~ Amateur Radio - K2GKK ~ ~
~ ~ USAF and FAA, Retired ~ ~
~ ~ ~ Oklahoma City, OK ~ ~ ~
~~ ~ ~ "The Money Pit" ~ ~ ~~
~ ~ ~ ex-Palm Beach, 76 ~ ~ ~
~ www.gmcmhphotos.com/okclb ~
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
> From: Reo43@aol.com
> Date: Sun, 25 Sep 2011 09:31:36 -0400
> To: gmclist@temp.gmcnet.org
> CC: k2gkk@hotmail.com
> Subject: [GMCnet] Roof AC Rattles on startup
>
> On Sat, 24 September 2011 18:08 D C "Mac" Macdonald wrote: <in part>
>
> >>>>>>>>>>>>>>>>
> Figured I'd turn on the on-board air system just for grins. Great
> clattering and rattling occurs,
> but what the heck! Maybe it will just die and be done with it.
> <<<<<<<<<<<<<<<<<<
>
> Mac, about that "clattering and rattling" -
>
> This is for all of you with the original Duo-Therm roof air conditioner
> (and there are quite a few, judging from the coaches at Goshen at GMCMI). You
> can tell if you have an original Duo-Therm AC if you have a third control
> knob that controls the air flow to the front or the rear of the coach.
>
> These units use a piston type compressor which vibrates somewhat on the
> first startup, but they are mounted on rubber grommets so the noise in the
> coach should not be very loud, and should quiet down to a gentle "purr"
> within a few seconds. However, if you hear a very loud metal-to-metal hammering
> when the compressor first starts, then you probably have a mis-installed
> mounting bolt.
>
> The compressor is mounted directly above the mounting bolt hole located at
> the passenger side rear of the unit. We (Duo-Therm) provided a special
> mounting bolt that had a 1/2 inch thread at one end and several inches of
> thread at the other end. The installer was supposed to install the short end
> into the air conditioner, and if the bolt was too long for the roof thickness
> they were supposed to cut off the long threaded end to fit. However, I
> have seen many of these where the installer was too lazy to cut off the bolt
> so they put the long threaded end up, put a nut on the short thread, and
> cranked up the bolt. This forces the bolt against the bottom of the compressor
> - and you get a severe noise when the compressor starts.
>
> To check this bolt you have to remove the complete air box from the
> ceiling. If you find this bolt with the short thread at the bottom, then you will
> have this problem. Remove the bolt, cut it to the right length, then
> re-install it with the short thread turned up.
>
> I would have thought that after 30 years these problems would have been
> corrected, but I guess there were some owners that just thought that was how
> they were supposed to work - I found a 1977 Birchhaven in 2010 that STILL
> had this problem. This was a Coachmen built unit, and it reflects the
> typical poor workmanship that I have seen so many times in northern Indiana built
> RV's in the 70's and 80's. I am not trying to get an argument started with
> that statement - but I calls 'em as I sees 'em.
>
> Erv Troyer
> Lagrange, IN
> (26 years with Duo-Therm)
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| Re: [GMCnet] Roof AC Rattles on startup [message #144468 is a reply to message #144465] |
Sun, 25 September 2011 08:56 |
Erv Troyer
Messages: 125
Registered: February 2004
Location: Lagrange, IN
Karma: 0
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Senior Member |
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| k2gkk wrote on Sun, 25 September 2011 08:48 |
The "clattering and rattling" was from the
air suspension system's compressor, NOT the A/C.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~~ ~ D C "Mac" Macdonald ~ ~~
|
OOPS! Can't help you with that - sounds like it is tired - i.e. - worn out (?)
Erv Troyer Lagrange, IN
74 Sequoia
reo43@aol.com
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| Re: [GMCnet] Roof AC Rattles on startup [message #144469 is a reply to message #144465] |
Sun, 25 September 2011 09:07 |
PETEinLongBeach
Messages: 90
Registered: June 2007
Location: Long Beach, CA
Karma: 0
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Member |
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Erv,
When I first used my Duo-Therm I thought something was wrong with the compressor mounts. It generates an alarming amount of vibration/noise upon initial start up, but quiets down after a few seconds. I would not characterize it as a metallic hammering, but it seems to vibrate the whole roof when it starts. Perhaps this is due to the mounting bolt you mentioned. It wouldn't surprise me if this has gone uncorrected all these years, as the coach was not used much for camping and still only has 38,000 miles on it. I will check the bolt assembly and correct if needed.
Thanks very much for this obscure information - we wouldn't find it anywhere else !
Pete Smay
Long Beach, CA
1977 Kingsley
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| Re: [GMCnet] Roof AC Rattles on startup [message #144470 is a reply to message #144463] |
Sun, 25 September 2011 09:36 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Wow.. this is the best misdirected thread ever!..
That is some great information. My front main larger unit does this and the rear smaller shorter unit does not. I'll have to have a look. These units IMHO were some of the best made as proven by how many are stil funtioning. Given the ravages of exposed weather conditions, long lack of use periods and wet environments inside and out, other than oxidized flag terminal connections and fan motors need a re oiling after 30 years, they have held up so well and the capacitors are even still intact! I know we had a Duo Therm lawn mower as a kid with Clinton power. Unique dusl discharge design steel chassis. The handle flipped over to reverse directions, somthing OSHA would not approve these days allowing you close proximity to be the blade, (though somehow I've driven in snow and ice all my life W/O ABS and never crashed..HMMM) I know they also made water heaters as well, perhaps the source of the name?? Thanks.
John Lebetski
Woodstock, IL
77 Eleganza II
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