On Thu, 20 Sep 2007 12:47:43 -0700, firstname.lastname@example.org wrote:
If this is a typical "Rear Air" system you have to have the front
air on so the AC Compressor is running to have rear air.
Unless they have a positive refrigerant shutoff solenoid valve or a
thermal expansion valve (TXV) on the front heater box AC evaporator
coil, they can't run the back air only, because the refrigerant will
waste a lot of energy trying to cool the front AC coils.
Even with a TXV on the front evap core, you will waste some energy
chilling down the front evaporator coil till the TXV senses it's over
cold and throttles off the refrigerant flow. But it will work. You
just need a separate wire to engage the AC Compressor clutch from the
rear air controls.
Yes - on the heater hose from the engine if you catch it before the
Y splitter sending the hot water back to the rear heater.
If you want these to function as emergency heater water cut-offs in
case you spring a leak while on the road, you need to put positive
shutoff ball valves in both the supply and return lines. Otherwise
the system can and will still leak 'backwards' through the return
hoses - it's all pressurized.
--<< Bruce >>--
Thanks Bruce, I guess I wasn't clear. I don't want to run the a/c, I
just want blow non-hot air. For example, today it was 65 degrees and
sunny. Sitting in the parking lot the van gets very hot inside.
There is no reason to run a/c in those conditions, just turn on the
VENT to COOL. However, VENT COOL does not work in the back of the
van. If you select VENT (i.e. not a/c and not max a/c), then it
doesn't matter what you set the temperature selector to; it ALWAYS
blows hot air to the back. Even if nice cool (65 degree outside) air
is coming in the front vents, the back vent still have HOT air coming
I am coming to the conclusion that this is just a design flaw, a not-
supported feature. Basically if you use the rear fan you must either
HEAT or A/C. There is no other choice. For one thing, the rear fan
does not have any option for fresh air intake, which is a pity.
Apparently in my van, the rear heater coils are always flowing. If
the AC is on, the rear unit is BOTH HEATING AND COOLING the air. Not
very efficient -- to say the least. Perhaps my vacuum valve is not
working. I found a simple solution. In the summer months, I put a
clamp on the heater hose (just under the driver side running board)
and this prevent hot water from getting to the rear unit. If I get
tired of messing with the clamp, I may install a ball valve.
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