Electric Fan Opinion

[Trevor Jessie]

I drove the Ugly Bug around today to start working kinks out of it. First let me say "wow". It is amazing how much faster the Ugly Bug is than the Midget despite using the exact same drive train. I overheard several people comment today (as I was sitting at red lights) that it must be some sort of British Rat Rod. I'm quite stoked that people recognize it for what I've tried to make it.

Anyway... here is my question. I have a 10" electric fan mounted behind a newly recored vertical flow radiator. It seems to be doing the job quite well. I can run the car hard and when I stop the temperature hand creeps up to 185/90 and the fan kicks on and the temperature will stop to drop if I just let the car idle. So... should it be wired to switch off with the ignition or be allowed to run after the key is removed?

 

[Sarastro]

Good question, but I doubt it matters much. I've noticed that some of my modern cars keep the fan on after the ignition is off, so the fan operates independently. However, I have an electric fan on my Sprite, it's off when the ignition goes off, and that's just fine. After all, the original cooling system works that way.

I guess it also depends a lot on how much you trust the thermostat--if it stays stuck on, dead battery.

 

[regularman]

I drove the Ugly Bug around today to start working kinks out of it. First let me say "wow". It is amazing how much faster the Ugly Bug is than the Midget despite using the exact same drive train. I overheard several people comment today (as I was sitting at red lights) that it must be some sort of British Rat Rod. I'm quite stoked that people recognize it for what I've tried to make it.

Anyway... here is my question. I have a 10" electric fan mounted behind a newly recored vertical flow radiator. It seems to be doing the job quite well. I can run the car hard and when I stop the temperature hand creeps up to 185/90 and the fan kicks on and the temperature will stop to drop if I just let the car idle. So... should it be wired to switch off with the ignition or be allowed to run after the key is removed?

Off with the key. I don't have the time to get into it, but for God's sake off with the key. The engine is going to cool down without the fan continuing to run, trust me.

 

[spritenut]

Yes for safety sakes, off with the key.
Imagine working under the bonnet and the fan decides to kick on just as you drop the screwdriver down the front of the engine, or the breeze blows your shirt tail.
All modern cars do stay on but the first line in any manual is
to remove the battery cable, this is so the fan doesn't kick on when you are under the hood.

 

[leecreek]

Time for a relay.

 

[Trevor Jessie]

It is wired to a relay that is powered by the ignition circuit, so it currently shuts off with the key. I just had thought I should ask the question since I knew some moderns will run the fan after the ignition is off.

Thanks for the opinions.

 

[tosoutherncars]

Yup... and I've never really understood what good an electric fan would do after shut-down if the water pump is mechanical. If the coolant is no longer circulating, what good is cool fluid in the rad?

 

[Trevor Jessie]

I dunno, but I would assume there would still be some convection within the fluid because of the temperature difference.

There are some old water cooled engines that do not have a water pump. (I'm thinking tractor)

 

[PAUL161]

I dunno, but I would assume there would still be some convection within the fluid because of the temperature difference.

There are some old water cooled engines that do not have a water pump. (I'm thinking tractor)

Early Model T Fords had no water pump. Water circulated by convection. A pump was installed on later models and was operated by a flat leather belt. Who said serpentine belts were new?

 

[Morris]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Who said serpentine belts were new?[/QUOTE]

Was it made out of snake skin?

 

[GeeBee1]

I dunno, but I would assume there would still be some convection within the fluid because of the temperature difference.

There are some old water cooled engines that do not have a water pump. (I'm thinking tractor)

Early Model T Fords had no water pump. Water circulated by convection. A pump was installed on later models and was operated by a flat leather belt. Who said serpentine belts were new?

Early MG's as well :wink:

 

[PAUL161]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Who said serpentine belts were new?

Was it made out of snake skin? [/QUOTE]

Never thought of that!

 

[glemon]

If you live in a hot climate I can think of some reasons you would want the fan to run after the car stops, mostly to cool off the engine compartment and carbs, many British cars I have had are hardest to start not in the cold, but after having shut down for 10 or fifteen minutes after being "rode hard and put up wet" on a hot day, don't know if the gas is boiling or vaporising in the carbs or what, but the usual trick is to give it some or a lot of gas to get it to start.

Even with the water pump off the air flowing to the block and moving in the engine compartment will cool things off faster.

I am not saying necessarily do it, but there are some reasons for it.

I suppose the fan could kick on while the you are under there, most electric fans are plastic and well shrouded, and many are mounted in front of the radiator, so I don't think we are talking about losing a hand or anything.

My concern would be running down the battery if it stayed on.

 

[RonMacPherson]

glemon makes a good point, which I was going to bring up, but will elaborate a bit on.


Almost all modern engines now come with lots of expensive electronics and a fairly high pressure fuel system, covered by a plastic shroud(s) on top of the engine. These things when shut off retain a LOT of heat.

So almost all modern cars now have fan timer relays, which will run the fan for anywhere from 30 seconds to 3 minutes(that I know of, may be longer for some cars that I don't pay close attention to). Then the timer relay opens and the fan turns off. You also will see a fan warning label on the upper radiator cross support or radiator fan shroud for all these engines, warning you that the fan may turn on at any time.

 

[Trevor Jessie]

So if I consider anything it should involve a timer relay to avoid running down the battery. I think I could wire something up such that the timed circuit becomes active once the ignition is off. But I think it is going to be OK. I haven't seen it go much above 195 once shut off (and that was sitting in the hot sun with no breeze).

 

[DrEntropy]

I wouldn't be too anxious to start burdening the beast with more gizmos. If the fan works with the iggy, you have what you need, IMO. One more relay means one more component to fail.
Leave "complexity" to th' Germans.

 

[Trevor Jessie]

I'm not going to do it immediately, but if (later in the summer) I see the temperature creep to uncomfortable levels then I'd like to have some options.