Home » Public Forums » GMCnet » Have you run an extra evaporator?
| Have you run an extra evaporator? [message #358661] |
Tue, 15 September 2020 09:43  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Bob Dunahugh called and asked about running a second evaporator. Well, do know a lot about refrigeration, but I have never had anything to do this. If you can contact him and guide him, he would appreciate that.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Have you run an extra evaporator? [message #358665 is a reply to message #358661] |
Tue, 15 September 2020 10:47  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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As far as I know. You just T it into the existing Lines. The aux evaporator will have it's own expansion valve.
Jim K I know will instruct as his vintage air kit is just that. a couple T fittings.
you do have to have somewhat of a balance, to what the compressor and the evaporators can do. The old a-6 compressor can handle most sizes, but if you put two larger Aux evaporators off a sandeen, you will have some issues.
been getting a crash course in aux evaporators this past year.... it should be simple, but it is not as simple in some cases. I currently believe I have too small of an aux evaporator, and I did not tie it to the OEM. so I will be swapping out the 13700 btu evaporator and install one 2x that BTU rating for next summer. I was not paying enough attention to the BTU ratings of some of the units last year, and how the vary.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Have you run an extra evaporator? [message #358681 is a reply to message #358661] |
Tue, 15 September 2020 23:36 |
Rick Staples
Messages: 126
Registered: May 2014
Location: Johnstown, Colorado, USA
Karma: -1
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Senior Member |
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Several years ago I added a second evaporator mounted under the co-pilot seat. (Credit to the late Jim Anstette for the idea.)
I put a cookie sheet (baking pan?) on the floor to catch the condensed moisture and lead it down through a tube in the floor. I bought (years ago) a rear A/C - heater unit from an ambulance on e-bay for parts. This unit is a bit bulky which made connecting the lines in the limited space a bit tedious. The dual squirrel-cage blowers are mounted on the back of the seat pedestal, tucked neatly between the pedestal and the dinette seat back. (My dinette is raised ~5" giving a little more room.) A couple of computer fan grilles keep fingers and debris out of the fans as they blow into the seat pedestal. Air travels forward through the evaporator which is located just ahead of the seat pivot post. The space forward of that (about 8" or so) serves as a plenum chamber (and a place to lay a few beverage cans for quick cooling). Cold air discharges through a couple of vents on the front left side of the pedestal, which can be aimed towards the driver or back towards the couch. A couple pieces of old vacuum cleaner hose (!) exit the front right corner of the pedestal, curve upward where they enter the armrest and discharge through another adjustable dash-type grille. If one needs a LOT of cool air (and the co-pilot is wearing insulated boots) we can just open the pedestal storage door and dump a huge blast of cold air. A fan switch is also mounted on the co-pilot's armrest.
The refrigerant lines were easier than expected. A couple of tee fittings near the receiver-dryer feed a pair of hoses running rearward outboard of the A/C compressor, then up through the floor to connect to the evaporator. Of course the compressor is still controlled by the original dash air thermoswitch, so the dash air must be on for things to work. It works about as well (or poorly) as it ever did. No special refrigerant valves or controls were needed. Dura-Cool (thanks Emery!) does the work. The GMC's A6 compressor is about the most powerful ever made for a passenger car (45,000 btu/hr), so it has no trouble pumping the refrigerant. I figure it's about as powerful as my home's central A/C system.
Does it work? Does it ever! Puts out at least as much air at a MUCH lower temperature than the original dash air. We are COOL! Best modification I ever did.
HTH,
Rick Staples
Rick Staples, '75 Eleganza, Johnstown, CO
"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
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| Re: Have you run an extra evaporator? [message #358682 is a reply to message #358665] |
Wed, 16 September 2020 00:10 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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Senior Member |
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lqqkatjon wrote on Tue, 15 September 2020 08:47As far as I know. You just T it into the existing Lines. The aux evaporator will have it's own expansion valve.
Jim K I know will instruct as his vintage air kit is just that. a couple T fittings.
We have one of JimK's installations, with the original S6. We have a '74, so the dash air is not great. Works fine. Sometimes just the fan stirs the air enough to make Ruth happy. On AC mode you can adjust either the dash or the auxiliary unit and the compressor engages. If it is getting too cold sometimes I run the dash fan on slow to keep the compressor from coming on too often.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: Have you run an extra evaporator? [message #358788 is a reply to message #358764] |
Sat, 19 September 2020 12:37 |
Hal StClair
Messages: 971
Registered: March 2013
Location: Rio Rancho NM
Karma: -12
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What did those two evaporators come from? Aftermarket?
Hal
"I enjoy talking to you. Your mind appeals to me. It resembles my own mind, except you happen to be insane."
1977 Royale 101348,
1977 Royale 101586, Diesel powered,
1974 Eagle Bus 45',w/slideout,
Rio Rancho, NM
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| Re: Have you run an extra evaporator? [message #358826 is a reply to message #358661] |
Mon, 21 September 2020 07:48 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Sean, why the solenoids? GM never used them on OEM vehicles with rear air, they just let the expansion valves handle it.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Have you run an extra evaporator? [message #358838 is a reply to message #358824] |
Mon, 21 September 2020 20:51 |
Rick Staples
Messages: 126
Registered: May 2014
Location: Johnstown, Colorado, USA
Karma: -1
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Senior Member |
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Sean,
Impressive system! What I want to know is does the original dash air still work? ie: Do you have THREE evaporators in your system? I always wondered if that's possible.
Rick Staples
Rick Staples, '75 Eleganza, Johnstown, CO
"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
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| Re: Have you run an extra evaporator? [message #358965 is a reply to message #358661] |
Sat, 26 September 2020 10:38 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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I'm missing something here. My Suburban had only expansion valves on both evaporators, and they only ran when the fan(s) were running. GM saves a nickle every chance they get.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Have you run an extra evaporator? [message #359045 is a reply to message #358965] |
Mon, 28 September 2020 12:50 |
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SeanKidd
Messages: 747
Registered: June 2012
Location: Northern Neck Virginia
Karma: 4
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Senior Member |
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It’s my impression, that on a warm system, the txv will operate, until the sensing element reached temperature then, txv would close, if the fan was off, evaporator would still get cold, bleeding off some energy. The solenoid is normally closed (NC) therefore no loss to the system until cooling was selected ( opening the solenoid and allowing the txv to operate). I can still run the fans in “vent” mode just circulating air If I want (these are cooling only with no hot water coil)
Sean
Sean and Stephanie
73 Ex-CanyonLands 26' #317 "Oliver"
Hubler 1-Ton, Quad-Bags, Rear Disc, Reaction Arms, P.Huber TBs, 3.70:1 LSD Honda 6500 inverter gen.
Colonial Travelers
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| Re: Have you run an extra evaporator? [message #359104 is a reply to message #358661] |
Wed, 30 September 2020 07:19 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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The suburban rear was recirculate so vent mode wasn't there. If you use it as a vent only, the valve would be a necessity.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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