electric radiator fans power savings

[blueovalz]

No great discovery here, but, after some experimenting, I found out that with enough forward velocity, that the fans windmilling will actually put a small charge back into the battery. What this means to me is that the amp draw listed by the manufacturer, is with the car at rest. Once up to speed the current draw become less and less as the ram effect of the air being pushed into the radiator becomes greater with higher speed. This explained the lessened current draw off the battery at speed before I installed the alternator. But at speed I did not need a fan anyway. Just an observation FYI

[Guest Aaron]

So, would it be possible to put some sort of speed switch on your speedo to turn the fans off at say 45-50 mph? Then you would only have the free charging of the fans.

[Modern Motorsports Ltd]

"So, would it be possible to put some sort of speed switch on your speedo to turn the fans off at say 45-50 mph"

Many of us run adjustable thermo switches, mines set at 190 and I run a 180 Tstat. Once rolling unless you're roadracing IME, the car cools easily without any fan input, hence I rec'd a temp-related switch (ie. no point having it on all times). My rad got very low in fluid over the last while....yesterday my coolant temp went from 185->222 F in right about a minute while sitting at a light. Less than 20 seconds of rolling and it was back below 190. I added 4+ litres to it today (got a fix I need to do).

 

YMMV depending on rad/water pump/fan etc.

[Guest tom sixbey]

thats funny - i was wondering about this just the other night... i noticed my battery was charging a lot with the fan on at about 70 MPH.. could this be the windmill effect you guys speak of, or a bad voltage regulator?