electric cooling fans

[kglowacky]

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

[RustyPile]

Originally Posted by kglowacky

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

Changing to a different fan probably won't cure your voltage drop problem.. Fans that have good cfm ratings draw about 20 amps each. That's 40 amps just for the fans. They should be relay activated and the wiring should be no less than 10 gauge.. If the fans are wired on separate circuits, 12 gauge will work.. If your alternator is less than 85 - 90 amps output, that's part of the problem..

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..

[kglowacky]

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.

[Joyridin]

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.

[kglowacky]

What is PMW?

[Joyridin]

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