How to vent cool air to the rear fan? Econoline-150 Waldoch conversion

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

jdhenckel@gmail.com - 20 Sep 2007 20:47 GMT

I just bought a used 94 Waldoch conversion with a rear heat/ac unit by
Pro-Air. The rear heat and a/c work just fine. However, when I turn
a/c off and set control to VENT and temp to COOL and turn rear fan ON,
then WARM air comes out of the rear blower. Is that normal?

I already read the "Van Conversion Manual" here (http://
www.proairllc.com/manuals-catalogs.html) but it does not say anything
about blowing cool air with a/c off. So I wonder if it is "not a
supported feature" ??

I am thinking about installing a shutoff valve such as this page,
http://www.panteraplace.com/page152.htm. If I do that, is there a
place I can put the valve so that it can shut off both the front and
rear hot water flows at the same time?

Thanks for any advice.

john

http://formulus.com/fave.php

Reply to this Message

Bruce L. Bergman - 21 Sep 2007 03:06 GMT

>I just bought a used 94 Waldoch conversion with a rear heat/ac unit by
>Pro-Air. The rear heat and a/c work just fine. However, when I turn
[quoted text clipped - 5 lines]
>about blowing cool air with a/c off. So I wonder if it is "not a
>supported feature" ??

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.

>I am thinking about installing a shutoff valve such as this page,
>http://www.panteraplace.com/page152.htm. If I do that, is there a
>place I can put the valve so that it can shut off both the front and
>rear hot water flows at the same time?

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 >>--

Reply to this Message

jdhenckel@gmail.com - 24 Sep 2007 14:47 GMT

> >I just bought a used 94 Waldoch conversion with a rear heat/ac unit by
> >Pro-Air. The rear heat and a/c work just fine. However, when I turn
[quoted text clipped - 35 lines]
>
> --<< 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
out.

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.

John

Reply to this Message

Backyard Mechanic - 21 Sep 2007 15:14 GMT

> I just bought a used 94 Waldoch conversion with a rear heat/ac unit by
> Pro-Air. The rear heat and a/c work just fine. However, when I turn
> a/c off and set control to VENT and temp to COOL and turn rear fan ON,
> then WARM air comes out of the rear blower. Is that normal?

Yes it is normal.

You are right that hot always flow through heater in most Ford cars.
Including 'Dual Heater'

There is usually no outside air into the rear unit, it is recirculate-
only

Many engines count on the heater flow for the coolant bypass necessary
during warmup. It's important that you dont shut this off completely. So
you have to make sure there is a circulation path for the coolant before
the thermostat opens, in fact the thermostat works better in this
scenario.

THAT said, you can go to HD or Lowes and get a valve like the one you
referred to and install it in the line to the REAR heater assy, as long
as the front continues to recirc coolant. It really wont matter which
line you put it in, as long as flow is stopped. Look for the valves that
come manufactured with the barb nipples.

If you stop flow to BOTH cores, you have to make sure there is a
continuous flow from the top of engine back through waterpump. If not
existing, and you want to shut off ALL heater flow, then you need to put
in tees on the engine side of valved heater lines and allow small but
reliable flow path, suggest 1/4 inch line minimum.
Like I said, the latter is not necessary if you only shut off flow to the
back.

Signature

Yeh, I'm a Krusty old Geezer, putting up with my 'smartass' is the price
you pay..DEAL with it!

Reply to this Message