Electric cooling fan current draw, engine idle speed
06-12-2016, 12:08 PM
#1
Le Mans Master
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St. Jude Donor '05, '09, '15
Electric cooling fan current draw, engine idle speed
I am in the process of getting my 65 running again after an accident. I had to replace the radiator and fan so I changed from the belt driven fan to a DeWitts BB aluminum rad with dual Spal fans. They work fine and cycle on and off as they should. Problem is when they cycle on the engine speed drops about 200 RPMs. I guess from the increased load on the alternator . Is this normal?
Thanks
Tom
Thanks
Tom
06-12-2016, 12:20 PM
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Weak battery?
06-12-2016, 03:22 PM
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I am in the process of getting my 65 running again after an accident. I had to replace the radiator and fan so I changed from the belt driven fan to a DeWitts BB aluminum rad with dual Spal fans. They work fine and cycle on and off as they should. Problem is when they cycle on the engine speed drops about 200 RPMs. I guess from the increased load on the alternator . Is this normal?
Thanks
Tom
Thanks
Tom
Last edited by Geralds57; 06-12-2016 at 03:23 PM.
06-12-2016, 05:44 PM
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It depends on how many amps your fans are pulling and how many amps your alternator is putting out.
06-12-2016, 06:20 PM
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06-12-2016, 06:46 PM
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I upgraded my alternator when I added a SPAL fan. My battery gauge needle swings to the left momentarily but rpms don't drop.
Steve
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06-12-2016, 08:23 PM
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I ran an extra 12gauge wire from the alternator to parallel the original wire (the original wire is spliced into the new 12gauge with a pigtail wire running to the horn relay to power those things running from the relay terminals) to the starter, just like the original. the fan power & controller were spliced into the new 12gauge, the old wire continues to 'power' the rest of the car.
because part of the circuit no longer runs thru the ammeter, it is not exactly accurate anymore; but, who cares....
other than feeling like I've been 'kicked in the chest', I'm doing fine... thanks for asking...
Bill
Last edited by wmf62; 06-12-2016 at 08:28 PM.
06-12-2016, 09:13 PM
#10
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St. Jude Donor '05, '09, '15
Sorry I left some info out. I have a new AAW wiring harness and my old 100A Power Master alt. Charging wire from alt is 6 gauge to battery. Battery cables are 2 gauge Pos and Neg. Fans are powered by an 8 gauge wire from main fuse panel to an aux fuse block next to the fans. 2 30A fuses with 10 gauge wire to separate 40A relays. One for each fan. Fans are grounded to frame. I feel good about the circuit capacity. The engine is a modified 355. Probably 425 hp. Maybe it has to do with the cam grind?
Thanks
Tom
Thanks
Tom
Last edited by Sky65; 06-12-2016 at 09:22 PM.
06-12-2016, 09:33 PM
#11
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I have spalls on my old Cherokee (with a circa 1988 chevy 350). their web site will tell you exactly how many amps they draw, mine draw 40amps each on startup.
while you're at it, may also want to check to see if output wire on your alt needs to be upgraded. and make sure you connect them to properly rated relays.
edit-- looks like you already took care of the wiring.
powermaster is a decent alt -- I have their 200amp, but 100amp should be more than enough, assuming you're not running a crazy 'thump'n stereo or other large draw.
FWIW, I had a 110amp alt in my Cherokee w/ 3x spalls, before upgrading to a 200 amp power master, the rpms did dip momentarily (a second or two) when they kicked in. Now I notice nothing.
while you're at it, may also want to check to see if output wire on your alt needs to be upgraded. and make sure you connect them to properly rated relays.
edit-- looks like you already took care of the wiring.
powermaster is a decent alt -- I have their 200amp, but 100amp should be more than enough, assuming you're not running a crazy 'thump'n stereo or other large draw.
FWIW, I had a 110amp alt in my Cherokee w/ 3x spalls, before upgrading to a 200 amp power master, the rpms did dip momentarily (a second or two) when they kicked in. Now I notice nothing.
Last edited by JMG2; 06-12-2016 at 09:36 PM.
06-13-2016, 08:12 AM
#12
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St. Jude Donor '05, '09, '15
Dewitts told me the fans draw 26 amps total when running. Did not mention startup amps. I bumped the base timing up a little and it seemed better. I have to "clearance" one if the header tubes. Then I'll get back to it.
Thanks
Tom
Thanks
Tom
06-13-2016, 11:46 AM
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Steve
I ran an extra 12gauge wire from the alternator to parallel the original wire (the original wire is spliced into the new 12gauge with a pigtail wire running to the horn relay to power those things running from the relay terminals) to the starter, just like the original. the fan power & controller were spliced into the new 12gauge, the old wire continues to 'power' the rest of the car.
because part of the circuit no longer runs thru the ammeter, it is not exactly accurate anymore; but, who cares....
other than feeling like I've been 'kicked in the chest', I'm doing fine... thanks for asking...
Bill
I ran an extra 12gauge wire from the alternator to parallel the original wire (the original wire is spliced into the new 12gauge with a pigtail wire running to the horn relay to power those things running from the relay terminals) to the starter, just like the original. the fan power & controller were spliced into the new 12gauge, the old wire continues to 'power' the rest of the car.
because part of the circuit no longer runs thru the ammeter, it is not exactly accurate anymore; but, who cares....
other than feeling like I've been 'kicked in the chest', I'm doing fine... thanks for asking...
Bill
I upgraded to a 100 amp alternator because I have Vintage Air and a DeWitt's/Spal Combo Fan. I didn't change any of the car's wiring.
I didn't install the combo fan or the A/C but the fan was set up to take power directly from the alternator's power supply post and the A/C was set up to take power from the starter. FTF advised me to switch to the horn relay as a power source for the A/C to resolve a battery gauge aberration so I changed it and all is good.
"Kicked in the chest" by an angry mule is probably more accurate than just "kicked in the chest" <LOL>.
Steve
06-13-2016, 12:34 PM
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St. Jude Donor '07
With a 140 amp alternator, you must be running more stuff than just a fan.
I upgraded to a 100 amp alternator because I have Vintage Air and a DeWitt's/Spal Combo Fan. I didn't change any of the car's wiring.
I didn't install the combo fan or the A/C but the fan was set up to take power directly from the alternator's power supply post and the A/C was set up to take power from the starter. FTF advised me to switch to the horn relay as a power source for the A/C to resolve a battery gauge aberration so I changed it and all is good.
"Kicked in the chest" by an angry mule is probably more accurate than just "kicked in the chest" <LOL>.
Steve
I upgraded to a 100 amp alternator because I have Vintage Air and a DeWitt's/Spal Combo Fan. I didn't change any of the car's wiring.
I didn't install the combo fan or the A/C but the fan was set up to take power directly from the alternator's power supply post and the A/C was set up to take power from the starter. FTF advised me to switch to the horn relay as a power source for the A/C to resolve a battery gauge aberration so I changed it and all is good.
"Kicked in the chest" by an angry mule is probably more accurate than just "kicked in the chest" <LOL>.
Steve
I am no longer using the Lincoln Mark VIII fan as I managed to burn up a couple of expensive controllers through some dumb things I did, so I'm back to the mechanical flex fan.
BUT I do have the a/c and a condenser pusher fan to run, and I have plenty of amps to spare...
and, you are correct in what you did with your wiring as my ammeter is no longer accurate because the additional wire splits the current flow (only part going through the gauge); but then I don't care how accurate the gauge is..
Bill