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Bandit,
thanks for chiming in. That info is very informative and something car cars should consider when buying parts It pays to have engineers around. Good stuff
I have the same Windstar fan setup in the LS powered 72 A-body wagon in my avatar.
I run this dual relay setup in mine...
These are 70 amp relays...I'd have to look, but I think I run 30 amp fuses for each fan...never had a problem running both or just one. (I trigger mine with the factory ECM)
I know this is probably a mute point if your going PWM.
70/71 Vett as I remember. I had to cut them way down as you can see. One row off the bottom and the rearward splay. I in-layed them so the fit was perfect. Took a ridiculous amount of time but so didn't the entire resto.
thanks for chiming in. That info is very informative and something car cars should consider when buying parts It pays to have engineers around. Good stuff
Any time. You can find a lot of fuse performance curves here: https://www.eaton.com/us/en-us/produ...nt-curves.html The trick is knowing the magnitude and duration of the inrush current for a given fan & electrical circuit.
To illustrate the difference in fuse form factor, l'll propose a hypothetical. Let's assume the fan draws 20amps when running continuously. The inrush current to start a DC motor can be 2-3times the running current (rule of thumb), so let's assume 2.5x or 50amps. If you have a 30amp ATM fuse, based on the performance profile linked, it will last less than 3sec before the fuse blows at 50amp. If you use a 30amp MAXI fuse, you'll get 40sec before the fuse blows. If that 50amp inrush current only lasts say 5miliseconds, that would be a difference of 600 starts for the ATM vs 8,000 starts for the MAXI. Both are 30amp rated, but there is a significant difference in how many times they can start the fan before they blow.
Electrical engineers have several techniques available to limit inrush current so these things don't happen. I'm a mechanical guy so my knowledge is limited.
And part of the reason for the PWM/variable current controllers is they "soft start/stop" the fans significantly reducing the inrush - and a similar thing happens when they turn off - you get a "spring" like bounce of voltage. I had mine on the stereo circuit and the starter (big mistake), and every time I'd start the car, the voltage spike/drop was low enough to clear my presets. Duh.
I'm also building a 70' chevelle with windstar fans. Originally was going to do 2x 30-40A relays, which can set you back $60-90 once all said and done, not to mention it burns up an ECU output.
Thanks to the suggestions above, I looked into the Northern Rad PWM (Spoke to Carl from Vaporworx yesterday, who was part of bringing this to market, and also running his Vaporworx PWM for my fuel module) and am sold on the concept due to these benefits:
Costs about $175, not much more than relays.
Standalone, does not require ECU ouput. Will be using termx with only 4 avail.
Soft start
Super simple wiring
Small in size (I was also looking at DCC and autocoolguy)
I'm also building a 70' chevelle with windstar fans. Originally was going to do 2x 30-40A relays, which can set you back $60-90 once all said and done, not to mention it burns up an ECU output.
Thanks to the suggestions above, I looked into the Northern Rad PWM (Spoke to Carl from Vaporworx yesterday, who was part of bringing this to market, and also running his Vaporworx PWM for my fuel module) and am sold on the concept due to these benefits:
Costs about $175, not much more than relays.
Standalone, does not require ECU ouput. Will be using termx with only 4 avail.
Soft start
Super simple wiring
Small in size (I was also looking at DCC and autocoolguy)
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