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#1 |
Registered User
Join Date: Mar 2020
Location: The Woodlands,Tx
Posts: 574
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electric cooling fans
Thinking of replacing my current junkyard Dodge dual cooling fans with a new set. I would like to get some that draw less amps than my current ones. Not sure what mine draw but when they turn on it drops the amp gauge below 11. Anyone using a set that bolts right in and are happy with them? would like a one piece 2-unit bolt in. Again got these out of a junkyard 5 years ago and the alt. works fine while running everything else until they come on. During the day all good at night when it drops. Had alt checked it is 110 amps. all good.
Thanks Can someone move this to electrical. Thanks Last edited by kglowacky; 08-15-2024 at 07:39 PM. |
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#2 | |
Registered User
Join Date: Dec 2017
Location: Elkhart, Texas
Posts: 1,694
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Re: electric cooling fans
Quote:
My truck had a 78 amp alternator when a previous owner converted to internal regulator. I installed dual fans and the 78 amp alternator would just barely keep up.. At night with lights and AC running, it simply wasn't enough alternator.. I switched to a 100 amp alternator, 8 gauge charging wire to the battery and problem solved.. |
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#3 |
Registered User
Join Date: Mar 2020
Location: The Woodlands,Tx
Posts: 574
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Re: electric cooling fans
I have a 110 alt. I have a LS 1 swap. The new gauge wire is 10 on the fans to a separate relay for each fan. I am thinking the old Dodge fans are drawing more then 40 based on the fact the original wire looks like 8 or 10. ( I spiced in before the original plug of the fan unit.) Looking at some new replacement fans the wire size appears to be 12 or 14. or I will need to upgrade my alt to 120/130. trying to avoid this.
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#4 |
Registered User
Join Date: Sep 2020
Location: Cleveland, Ohio
Posts: 530
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Re: electric cooling fans
Changing from relays to a PMW set-up will do wonders. The fans come on slowly as needed and only hit full speed if needed. I have twin fans in my C10 and you can't see the volt gauge move at all driving in any temperature.
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#5 |
Registered User
Join Date: Mar 2020
Location: The Woodlands,Tx
Posts: 574
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Re: electric cooling fans
What is PMW?
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#6 |
Registered User
Join Date: Sep 2020
Location: Cleveland, Ohio
Posts: 530
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Re: electric cooling fans
Pulse Width Modulation. GM uses it on their electric fans and fuel pumps.
Instead of the fans coming on full blast and a specified temperature, then shutting off causing a huge load to be dumped on your alternator, you set the temperature down a bit lower and as the vehicle gets warmer, the fans slowly come on. If/when it hits your maximum temperature, the fans will be running at full speed. Most of the time though, that doesn't really happen because the fans have been running at half speed keeping the temperature in check. GM has used this on their fuel pumps since around 2015, maybe a bit earlier. Since the fuel pumps are being modulated constantly, there is not need for a return line. When the car needs more fuel, they speed up the pumps. When you are idling, the pumps run slow. It saves the pumps and again, reduces the need for huge alternators that are capable to handle the huge load dumped on them. Here is the fan unit I used. I have the HF-125 for my twin Derale fans. Supposedly the Derale PMW unit is not too good. https://www.autocoolguy.com/home I heard a few people use this one also. I have never used it. It is available at several places. https://www.northernradiator.com/HIG...S?pageSize=200 Last edited by Joyridin; 08-16-2024 at 03:28 PM. |
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#7 |
Registered User
Join Date: Jun 2015
Location: Carlos MN
Posts: 2,042
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Re: electric cooling fans
Over on LS1tech.com in the "conversions" forum there is a thread dedicated to PWM fans.
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#8 |
Registered User
Join Date: Mar 2020
Location: The Woodlands,Tx
Posts: 574
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Re: electric cooling fans
Good info. But not sure it will help my problem. which is I am wired that when I turn on my A/C the fans through 2relays turn on, this draws my volts at idle negative, It has nothing to do with engine temp. I know what you are going to say is then this is a problem when the pcm turns on both fans for engine temp. Yes and no. Most of the time the pcm only turns on the first fan and that is enough to cool the engine down and not draw enough amps to make me negative, The second fan when turns on is usually a short duration and I am running down the road at enough rpms to keep me positive. So I think I need smaller amp drawing fans so at idle I am positive,. Down here in Houston I got to run A/c almost always. . Beware I am very poorly educated in electric amps and volts so if this makes no sense I understand.
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#9 | |
Registered User
Join Date: Sep 2020
Location: Cleveland, Ohio
Posts: 530
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Re: electric cooling fans
Quote:
Either way though, you have some other issue. Here are the fans I am running. These work cherry on my truck. I have A/C, electric fans, Dakota gauges, decent stereo, and a bunch of other electric items and the alternator doesn't drop a bit when the fans kick on. https://www.summitracing.com/parts/der-16927 |
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#10 |
Registered User
Join Date: Mar 2020
Location: The Woodlands,Tx
Posts: 574
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Re: electric cooling fans
thank you I will look ino this fan set up
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#11 |
Senior Member
![]() Join Date: Dec 1999
Location: Southern California
Posts: 2,804
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Re: electric cooling fans
Good to the see the full amp draw does not change with the PWM setup was mentioned. With PWM control you get less heat at motor with variable speed or lower speed set points. There is some heat generated at controller. It is much less than a variable voltage setup though because voltage remains constant @ 12v.
A few remarks- note that typically a lower watt fan (lower amp draw) will move less air. With a good fan setup you do not necessarily needs fan/fans at full speed with A/C on. Am using a single oem 850 watt 19" PWM fan on my truck. The PWM signal is coming from the stock e67 ECU. A pressure sensor in the A/C lines sends information to ECU which will command fan @ 50% duty cycle when it is required. This method only turns fan on when needed, when pressure rises. ie- low speed or around town driving. Fan really not needed at highway speed. The duty cycle (fan speed) will change with engine cooling needs as well. The higher speed always takes priority.
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