I finally got around to installing some elec. dual fans in my car this weekend (thanks for the upper mount duff!). Anyway, they can't be pulling more than 25 amps (have it on a 30 amp circuit breaker but tested it on a 25 amp fuse). but everytime I turn them on I get a wicked power surge through the car. The glaring check engine light (no computer) goes dim than comes back normal. I can live with this. I cannot live with however than when turning the fans on with the headlights on that the headlights go dim and are at about half power. The alt reads 13 - 15 during cruise and sometimes dips down to 11 at idle understandably. The alt. has always been sufficent on the car it's hard for me to believe that the dual fan cars came with a higher amp alt. Any info will be greatly appreciated. Thanks!

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1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration
13.98 @ 101

 

In this weather, I only use one fan, if I even drive my camaro at all. In the summer, I have the one fan running all the time, until I get off my lazy can and get it wired into the A/C. I also ran the power directly from the battery, using a seperate 30 amp fuse for each fan. It worked great all summer!

Good luck!


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Working on:
'84 Z28 LG4 305
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350
using primarily GMPP parts.
Block is in shop!

ASE Certified Master Tech

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I have them both off of one 30 amp relay (powered from the battery). so I put the the one fuse so I didn't melt a relay on accident. Thanks for the tip. I may just run one fan (so damn cold in Ohio if not for idle I could probably get away with running no fans).

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1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration
13.98 @ 101

 

FTA,

For about twenty bucks you can install an AutoMeter fan control switch and make the circuit a little more automatic. The fans probably wouldn'y even turn on most of the time, at least until April or so....

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Later,
Vader
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"I cannot take this any more... Saying everything I've said before..."
Adobe Acrobat Reader 4.0

 

Maybe I am crazy, but 25 amp is alot for fans. Normal electric motors of about that size usually only pull around 7 amps (haven't check a fan motor recently), but 25 is alot, are you sure the motors are OK?

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WHen I first installed mine, I had them running on 1 30 amp fuse, and it would blow when the fans kicked on. I think that while running, the current would be more like 10-15 amps, but the startup current to get the fans running is higher, and the fuse is just to protect the wiring.

I am running the stock dual relays also (I scored the whole mess, fans, wiring, relays, and mouting brackets for about $30, and I pulled everything myself so I knew I would get the right stuff!

I wish there was a switch that would only turn the A/C fan on when the pressure is high enough to need it, so that the fan wouldn't run while running down the highway.

Well, good luck with whatever way you decide to run it!

------------------
Working on:
'84 Z28 LG4 305
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350
using primarily GMPP parts.
Block is in shop!

ASE Certified Master Tech

Starting to look like the Kicker poster child!

 

I have a probe but its cold out and I wanted to run the override switch for a bit to make sure the fans worked before I wire it in permantely. The fans do not draw 25 amps, that was my test circuit. My cheap multimeter won't measure the current for some reason so I only have the amp guage on the battery charger. They kick in at about 9 ~ 11 amps and run around 6 ~7 amps each so combined would be around 12 ~ 14. The smallest circuit breaker I had was 30 amps and I'm a believer in something that auto resets that has this important of a function. The alt is stock so I may just get it tested.

------------------
1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration
13.98 @ 101

 

What do you have them wired to? It sounds to me like you probably have them hooked to the fusebox, which makes the current for them to have to go through a whole bunch of the car's wiring, such that it causes voltage drop in all those other circuits.

I would suggest getting their power either from the big starter terminal where the red battery cable goes, or the main terminal on the back of the alternator which also goes straight to the batt through large wire. Use an in-line fuse, like maybe one of those little rubbery ATO fuseholders. Get it off the fusebox.

It would not surprise me that cars with electric fans came with a higher output alternator than ones that didn't.

I believe I would have to lose the SES light bulb, it would drive me crazy... your insanity threshold must be higher than mine.

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"So many Mustangs, so little time..."

 

I measured mine and each fan pulls 21 amps at startup, they are old to. I should get new motors because some of you report only 10 amps at startup.

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86 Camaro Sport
383 Speed-O-Motive Crate Engine, Trick Flow Twisted Wedge G2's, 58mm Accel TB, 3.73 Auburn Pro, SLP Cold Air Induction and Headers, Dynomax Cat-back, Serpentine Belt Setup, Dual IROC Fans, Jamex springs, 16" IROC Rims, 36mm/24mm Sway Bars, Global West Steering Brace. Hotchkis Rear LCA's,Panhard Bar and SFC's.
My Camaro Project

 

Wiring is this.

Relay coil ground (electromagnet) to ground, relay coil hot to switch on interior that draws from the radio (nearest ign. hot and the coil only draws a couple mAs at 80 - 100 ohms). Then the supply voltage comes off the back of the alt to a fuse to the relay, then it goes to hot on each fan then each fan goes to ground. I've rewired many houses and when you wire up 5 4 pole switches in an attic in one box it makes this look rather simple

------------------
1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration
13.98 @ 101

 

That should definitely fly. The back of the alt is the second highest-current place in the whole car, so you'd think it should be OK. One other thing to check - where do the grounds go? best results would be obtained if they go to the block, rather than the chassis.

BTW I have spent most of the last 20 years as the chief engineer of TV and radio stations in major markets... car wiring doesn't scare me too much either! (at least when it hasn't been hacked)

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"So many Mustangs, so little time..."

 

I ran my grounds right to where the battery connect to the body for the body ground, and for the positive, I got one of those battery taps and bolted right to there. The realys mount right beside the battery in the stock setup anyway.

12 wiring in a car doesn't even phase me anymore. After working on the industrial equipment that I deal with daily, automotive electrical is simple as can be! You just have to remember the basics and not try to make things more difficult than they already are.

------------------
Working on:
'84 Z28 LG4 305
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350
using primarily GMPP parts.
Block is in shop!

ASE Certified Master Tech

Starting to look like the Kicker poster child!

 

All motors (AC or DC) will draw more current at start-up than during running. Like anything, it takes more energy to get something moving than it does to maintain that movement.

Both my electric fans will each draw ~22 amperes (at 14.1 volts) at start-up (in-rush current). This lasts for only a fraction of a second. Once they attain operating speed, current will be reduced to ~8 amperes (at 14.1 volts).

For that reason, you should calculate at least 30 amperes per fan for determining the fuse, fusible link or circuit breaker to use. (I prefer a fuse because when it opens, it will be permanent so any faults can be repaired - an automatic circuit breaker will restore the circuit when the breaker cools and repeat this cycle indefinately, allowing more chance of problems).

If you connect both fans together, figure that your total in-rush current will be about 45 amperes, and your run current will be about 16 amperes (based upon my measurements as described above). Often, the fuse rating is determined by adding about 50% to the current draw. This is just a guide.

[This message has been edited by Stuart Moss (edited January 12, 2001).]

 

Ah. I didn't even think of trying a non-chassis ground. I may just have to live with having too much power draw w/headlights on until I get another alt, good thing I do very little night driving.

------------------
1984 WS6 Trans Am Hartop
Former L69 Car under restoration
1984 WS6 Trans Am T-top car
4-bolt main 350, headers, Holley 650, T-5 and 3.23's.
Daily driver and restoration
13.98 @ 101

 

I feel better about my choice of fuse sizes after someone else agreeing! Actually, I came to my sizing conclusion, by trying to run both on the same fuse, it would blow a 25, but a 30 would hold. I know that you can double the actual amps for fuse sizing, therefore, I just threw in 2- 30's!



------------------
Working on:
'84 Z28 LG4 305
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350
using primarily GMPP parts.
Block is in shop!

ASE Certified Master Tech

Starting to look like the Kicker poster child!