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Topic: Dash AC low pressure switch (Read 249 times) previous topic - next topic

Dash AC low pressure switch

To the collective...

So, I am bewildered as to why FT did not use a low side switch on their Dash AC systems.  My coach ( a 2002 U320) as well as others I have seen appear to have the switch deliberately not used (switch installed but terminals capped).  My coach drawings show the switch but not wired. 

I know enough about refrigeration to understand the need for LP compressor cut out and would like to know FT's thinking and what they hoped to achieve.  I know the numbers, and realize the expansive line sets and other oddities associated with motor homes can result in lower than typical low side pressures, but there are appropriate LP switches that would allow for appropriate compressor cycling based on the system load ...

Any enlightenment would be appreciated...

Bob....
2002 U320
3620 PBDS
Build 5985
2021 Equinox Toad
Motorcade 19006 & all those "other" clubs too!

Re: Dash AC low pressure switch

Reply #1 –
The low pressure switch on my '99 is behind the condenser grill at the dryer filter.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Dash AC low pressure switch

Reply #2 –
Quote from: craneman –
The low pressure switch on my '99 is behind the condenser grill at the dryer filter.
That's where mine is on my 2003



Keith
The selected media item is not currently available.Keith & Jo
2003 U320T 4025 PBBS Designer series
Build 6203    Cummins 500hp
2000 U320 4010 WTFE / Build 5762 —Sold—
Motorcade #18070   
Pasadena, Texas
2015 Jeep Wrangler Sahara-Sunset Orange pearl coat
Don't argue with a fool, people watching might not be able to tell the difference.

Re: Dash AC low pressure switch

Reply #3 –
Wow! I gotta look for mine now.
Richard & Betty Bark & Keiko our Golden Doodle
2003 U320T 3820 PBDS
Build # 6215
MC # 16926
2016 Chevrolet Colorado 4X4 diesel

Re: Dash AC low pressure switch

Reply #4 –
Mine is  on my dryer.
Peter and Frieda Morin
1999 36ft. U320 Foretravel
Build # 5436
1998 Suzuki Sidekick Sport

Re: Dash AC low pressure swi

Reply #5 –
It's not an issue of where it's at...it's on the low side line at the compressor, where it should be.

  The issue is why FT opted not to use it and just cap the connector on it?  Funny thing is it is shown on. The FT dash A C wiring drawing....  Shown just out there in "space" not connected. 

There is a reason low side switches are installed....to protect the compressor from a low/no refrigerant flow condition.  To some extent the compressor depends upon the cold, expanded refrigerant to help cool the compressor.  It can cycle the compressor under periods of extreme cooling loads allowing the system to  catch up and not freeze the evaporator.  It's also an indicator of restrictions or other potentially detrimental conditions. 

So the question still remains, why did FT nope to not implement this standard safety feature?  This adds to my list of "what were they thinking" as I encountered many of those thoughts during my recent house DC system lithium upgrade..

Thanks!

"Bewildered Bob"...


2002 U320
3620 PBDS
Build 5985
2021 Equinox Toad
Motorcade 19006 & all those "other" clubs too!

Re: Dash AC low pressure switch

Reply #6 –
Mine is installed and hooked up. I'll check my print later if i get time. I have found several receiver dyers  corroded internally and although I dont understand how reccomend changing them anytime the system is opened. Being corroded causes large pressure splits with the expansion valve being restricted. Ive been using R/Ds with an external desiccant indicator.

Parker 3520-016 Receiver dryer

Re: Dash AC low pressure switch

Reply #7 –
Wonder if it came from the factory that way, OR if someone in the last 22 years has "re engineered" it.

Agree, there should be a low pressure switch to protect the compressor.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020