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99 AWD BadAstro
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Discussion Starter · #1 ·
Title says most of it, I ahve a conversion van and it has a rear heat setup, with a switch operable from the dash. I want to repurpose the vents in the 'wall' of the van so they are connected to my diesel heater system, so I don't need the rear heat setup anymore. Where do the heater lines run, and can you just unbolt them or do they need to be looped?
 

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Common Sense + Critical Thinking
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With a conversion van it's going to depend on what/how the aftermarket outfitter decided to proceed. Basically follow the lines up where they attach to the factory cooling system hoses and cap or remove the tees, depending on the setup.
 

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Discussion Starter · #4 ·
Thanks, figured it was pretty straightforward. Just checking to make sure it's not unexpectedly stupid.
 

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My van is not conversion. The rear heat comes out under the front seats and is supplied by a duct that comes down the doghouse. Just removed it to get to one of those pesky vacuum lines that controls it.
 

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My van is not conversion. The rear heat comes out under the front seats and is supplied by a duct that comes down the doghouse. Just removed it to get to one of those pesky vacuum lines that controls it.
Thats sounds the floor vent heat setting, the rear heat has its own heater core and fan, mounted in the side panel behind the drivers seat, and a separate switch. on the dash to control the rear fan.
 

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Thats sounds the floor vent heat setting, the rear heat has its own heater core and fan, mounted in the side panel behind the drivers seat, and a separate switch. on the dash to control the rear fan.
Exactly, unless it's an aftermarket conversion, then it's usually in the rearmost drivers side corner where our rear A/C sits.
 

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01 Astro Cargo RWD, 97 Astro Mark III AWD
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Just checking to make sure it's not unexpectedly stupid.
You did say it was a conversion.
Take mucho, mucho pics so we can start documenting this unexplained phnomenon.
 
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The rear heater lines on my 02' LT rusted out. Direct-fit parts are no longer available. The time and effort involved in fabrication did not make sense for my vehicle, which no longer sees Winter roads.

I updated to the valve used on Front-Heat-Only fans and let the rear lines go empty/dormant.

Some very minor rework of the vacuum hoses will also need to be done but it's a straightforward process.

GM Genuine Parts 15-5557 Heater Bypass Valve
 

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Hi.
I did this with my conversion van recently. There is a post on it somewhere. the rear heat and AC are just hoses threaded from front to rear.

for the heat I just removed the connections at the 6 port valve and placed a silicone U hose in their place. I left the metal part of the hose that runs across the engine in place but cut the rubber hoses out just past the ABS unit under the van.

for my AC It was similar. The rear was AC had just been ’T’ connected into the system. I j removed the t and put the two sections back together. I did find that there were no o rings when I disconnected, that would explain why I kept losing AC!

from there I just pulled everything out at the rear.

here are some random pictures of the removal process

Gas Auto part Metal Engineering Pipe


Motor vehicle Automotive tire Electrical wiring Automotive exterior Computer hardware

Electrical wiring Gas Cable Wire Electrical supply

Automotive exhaust Gas Household hardware Automotive fuel system Auto part


I mounted the heater underneath and used the space inside for a small fuel tank but that’s up to you.

i also used the roof vents at first but I did find that the distance from the floor up to the roof and then a couple of 90 degree turns really sucked the heat and flow out of the heater blower.

i ended up cutting the pipe back and placing the output just before the roof.

White Wood Automotive exterior Gas Wood stain

it’s not as elegant but the heat output is so much better now

hope this helps.
 

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Correctamundo! The U-hose in the rear heat defeat works, but I would always recommend replacing the bipass valve (aka the octopus) to the version WITHOUT rear heat (4 port) since this stupid valve loves to break apart after a few years and leave you overheating and stranded.
 
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