Author Topic: Electric fans  (Read 2588 times)

Offline dieselman123

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Electric fans
« on: June 27, 2019, 10:17:12 PM »
I have a 83 c10 with dual electric fans and want to know how to go about turning the fans off at higher speeds with A/C on. is there a way to wire this up
Gotta clean my back windshield cause I'm too busy kicking up dust

Offline VileZambonie

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Re: Electric fans
« Reply #1 on: June 28, 2019, 06:31:31 AM »
Why would you turn it off with the AC on? You need the fan to keep the high side pressure in range. You could install a pressure switch on the high side but it would hardly be worth it.
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Offline dieselman123

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Re: Electric fans
« Reply #2 on: June 28, 2019, 07:16:33 AM »
I feel as though there is no need to have the fans on while driving 50+ mph.....
Gotta clean my back windshield cause I'm too busy kicking up dust

Online Rapid Roy

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Re: Electric fans
« Reply #3 on: June 28, 2019, 09:42:03 AM »
Fans are necessary for system cooling.

You can connect a cut off switch on each one. Go for a drive.

Please report back with the results.
« Last Edit: June 28, 2019, 10:09:25 AM by Rapid Roy »
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Offline VileZambonie

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Re: Electric fans
« Reply #4 on: June 28, 2019, 11:45:43 AM »
Modern systems use a high side pressure transducer where the PCM closely monitors high side pressure. If it determines system pressure is in optimal range for conditions it can energize and de-energize the fan relay as needed. Unless you can closely monitor this you run too high a risk of damaging the system. Relying on ram air isn't good enough as high side pressure can climb too rapidly.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline bd

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Re: Electric fans
« Reply #5 on: June 28, 2019, 12:06:46 PM »
Why would you turn it off with the AC on? You need the fan to keep the high side pressure in range. You could install a pressure switch on the high side but it would hardly be worth it.

Modern systems use a high side pressure transducer where the PCM closely monitors high side pressure. If it determines system pressure is in optimal range for conditions it can energize and de-energize the fan relay as needed. Unless you can closely monitor this you run too high a risk of damaging the system. Relying on ram air isn't good enough as high side pressure can climb too rapidly.

Agreed.  A/C performance can suffer dramatically to the extent of blowing the pressure relief valve and releasing refrigerant into the atmosphere, to tossing belts, to damaging seals, switches and/or the compressor.
Rich
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Offline JohnnyPopper

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Re: Electric fans
« Reply #6 on: June 29, 2019, 02:52:43 PM »
I just installed a electric fan, with a thermo adjuster that has a temp probe.

I also have AC so thanks for the tip, I will adjust it to the lowest setting so it runs most of the time.

ALL I KNOW IS that I feel like I picked up15+ horsepower!

Does anyone know how much it takes to drive a five blade fan and clutch?

Must be a lot, because she acts like she just woke up and wants to run!
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Offline bd

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Re: Electric fans
« Reply #7 on: June 29, 2019, 04:20:41 PM »
Rather than have the fans turn on at low engine temperature, install a relay to override the temp control when the A/C compressor clutch engages.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline JohnnyPopper

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Re: Electric fans
« Reply #8 on: June 30, 2019, 05:47:49 PM »
THAT is an excellent idea!

Thanks BD!
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction

Offline roundhouse

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Re: Electric fans
« Reply #9 on: July 04, 2019, 09:13:57 AM »
Most modern cars run the fans when the AC compressor is on

Be pretty easy to use a relay that uses water temp and is over ridden by the AC compressor signal

https://youtu.be/-954_wpRWsQ

Offline Mario

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Re: Electric fans
« Reply #10 on: October 08, 2019, 07:35:40 PM »
Run one fan on with a relay based on temperature or A/C ON.  Run the 2nd fan on a manually switched relay.  You could have the 1st fan on a manually off circuit with the ground wire.  I know first hand that ram air from speeds above 25 mph is enough cooling especially with a large aluminum radiator.  As long as you're not in Arizona in mid-summer.   
Mario
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Offline 75gmck25

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Re: Electric fans
« Reply #11 on: October 10, 2019, 05:13:31 AM »
A/C performance is much better with consistent air flow, so I would set up one fan to run whenever the A/C is on, and then use a temp controller to turn on both fans when needed for cooling.  This is a very typical setup for modern cars.  There are aftermarket electronic controllers that do this, but they are usually quite expensive. 

My understanding is that both Volvo and Ford used similar high-amperage controllers that you could pull from the junkyard.  I think it was Ford Windstar that used the dual fan controller and there are quite a few conversion articles online.

Bruce