Why not use van's built in fan?

[KMAG YOYO]

The Fantastic Fan I had on my last rig was great, but I got to thinking, there is already a fan built into the dashboard. Why put a redundant fan in the ceiling, and reduce the stealthy profile?

I understand that a roof vent fan can suck the hot air out of the top. But the ventilation fan in the dashboard is very quiet, has several speeds and a cabin air filter.

Yes, the dashboard fan could run down your starter battery, but it wouldn't be so hard to wire the fan into the house battery with a relay that switches over when the motor starts.

Maybe someone has already figured this out?

 

[highdesertranger]

the factory fan is a energy hog. it's meant to run with the engine running. highdesertranger

 

[BigT]

I pulled this off the "Intraweb" just a moment ago.  It's for a VW Jetta so YMMV, but probably not by very much.

Fan Speed           With Recirculation           Without Recirculation

4                              19.8 Amps                           18.0 Amps

3                              11.5 Amps                           10.8 Amps

2                              6.8 Amps                             6.5 Amps

1                              3.9 Amps                             3.8 Amps

 

[highdesertranger]

and there you go, ^. highdesertranger

 

[BigT]

Fan Speed           With Recirculation           Without Recirculation

1                              3.9 Amps                             3.8 Amps

By comparison, the 3-speed Fantastic Fan only draws 3.0 Amps on its highest setting.

 

[GotSmart]

The Fantastic Fan I had on my last rig was great, but I got to thinking, there is already a fan built into the dashboard. Why put a redundant fan in the ceiling, and reduce the stealthy profile?

First things first.  Stealth is a mirage.  A roof vent is a common item on a van.  It is not an indication that it is a permanent dwelling.

I understand that a roof vent fan can suck the hot air out of the top. But the ventilation fan in the dashboard is very quiet, has several speeds and a cabin air filter.

Location location location.  A dash fan helps when you are in the front seat facing the front.  ONLY.  A roof vent helps with the rest of the van.

 

[LeeRevell]

Engine accessory electric motors are not designed for efficiency, as the gasoline engine is always running to charge the system.

 

[KMAG YOYO]

I pulled this off the "Intraweb" just a moment ago.  It's for a VW Jetta so YMMV, but probably not by very much.

Fan Speed           With Recirculation           Without Recirculation

4                              19.8 Amps                           18.0 Amps

3                              11.5 Amps                           10.8 Amps

2                              6.8 Amps                             6.5 Amps

1                              3.9 Amps                             3.8 Amps

Well that's just stupid. I had no idea.

 

[SternWake]

Those numbers BigT pulled as to amp draw, are very similar to what I have measured on my Dodge van's blower motor.


I toyed with your idea, and using a PWM motor speed controller to use an extremely low setting and figured it would still be annoying loud for overnight use, and draw between 1 and 2 amps, and would move less air than a 12v 120mm computer fan for 300% more amp draw

The windings in the motor would likely make a high pitched whining sound under PWM speed control too.  It would likely still be easily heard by any passers by even at a very slow speed.

I installed a new VDO blower motor last year.  When it is uncaged, spinning with no squirrel cage, it draws 1.2 amps at 14 volts, but when the cage is attached and installed in the Hvac box, I was measuring 18.3 amps at 14.7v.

The blower motor circuit was a problem circuit on my 89 dodge van.  I improved the speed switch contacts and connector, and ran 8awg replacing the 14awg from the speed switch to the motor and improved the ground too, directly to alt(-) stud.  The new motor with improved circuit moves as much air on Medium high as it did on high speed before.

 

[ascii_man]

How hard would it be mechanically to replace the factory blower motor with a Fantastic motor?

 

[highdesertranger]

well a factory fan motor is a squirrel cage type fan and a fantastic is a propeller type. so I would say pretty hard to impossible. besides a squirrel cage has a much higher cfm rating. highdesertranger

 

[SternWake]

How hard would it be mechanically to replace the factory blower motor with a Fantastic motor?

Yeah, it would be a lot less work to cut a hole in the  floor and install a computer fan  blowing filtered air upwards. or some other ventilation solution.

The Hvac squirrel cage fans have to fight a lot of resistance in narrow vents with a bunch of hard turns, a regular fan would not be as effective in its place.