At 01:22 PM 6/21/2003, Dave Cromwell wrote:

>This works well, except as soon as I shut the fan off the 16amp fuse pops !
>I guess I could put the hot wire on the lower speed of the radiator fan,
>but that isn't as efficient and the engine still heats up a little.

Send me a diagram of how it's wired...sounds like something is getting a
big inductive kick.  If you've just added something to the wiring in
Bentley, I have that.

>it. I put in a separate toggle switch so I could start the high speed
>radiator fan  while I'm still on the flat to keep it from overheating.

I don't understand -- there's an automatic system to take care of
this.  Temp goes up, the fan comes on.  Temp goes up more, fan cranks
up.  The system is designed to give noticeable movement of the gauge
between stages -- there's not a problem unless you've got the high-speed
fan running and the temp is still going up. You don't lose anything that I
can see by letting the system take care of itself like every other car on
the road since 1930-something, and I don't think you gain anything to speak
of by starting early -- you cool the radiator down and the engine
thermostat simply closes off the flow from the radiator -- aside from
cooling down the water in the radiator which I think is minor.  Lessee...

Suppose the radiator holds two gallons, assume heat capacity same as water
(it's really less).  Two gallons is 16lb, so cooling it off by 100 F will
get you 1600 BTU, or about 500 watt-hours.

Suppose engine puts out 44 Hp, or 60 kilowatts.  Assuming 1/3 efficiency
it's rejecting 120 kW as heat.  I found a study using an Alfa Romeo engine
where the engine output was 33 KW and heat rejection into the coolant was
25 kW, so I think it's fair to double that for your 60 KW engine running
flat out; therefor somewhat over 40 kW being rejected by the radiator.  So
it's putting out 40 kWh per hour, or 500 watt-hours every 45 seconds.  So
500 watt-hours could be significant or not, I guess.

But that still leaves the question of why it should be necessary in the
first place.  Answer: it shouldn't.  The Vanagon has a cooling system with
large capacity; if it's working right it should be able to handle even
extraordinarily adverse conditions and considerably larger engines.  If
it's not working right then it needs fixing, not a band-aid switch...

YMMV -- I guess.  :-)

d

--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"